Attention-deficit hyperactivity disorder (ADHD) and glial integrity: S100B, cytokines and kynurenine metabolism--effects of medication

Identification of immune cells and circulating inflammatory factors associated with neurodevelopmental disorders by bidirectional Mendelian randomization and mediation analysis

The roles of various immune cells and circulating inflammatory factors in neurodevelopmental disorders (NDDs) remain controversial. Therefore we employed a two-sample and bidirectional Mendelian randomization and mediation method to explore the causal relationships between immune cells, circulating inflammatory factors, and NDDs. All data were originated from Genome-Wide Association Study (GWAS) datasets. We found a significant positive causal relationship between 13 immune cells and autism spectrum disorder (ASD), including six CD8+ T cells, one CD3+ T cell, two CD20+ B cells, one CD38+  B cell, and two plasmacytoid DC. 9 inflammatory factors showed significant causal relationships with ASD: interleukins-7 (IL-7), interleukins-2 (IL-2), Interleukin-2 receptor subunit beta levels( IL-2β) and interleukins-18 receptor 1 levels (IL-18-R1) were negatively associated. In contrast, five inflammatory factors were positively associated, such as tumor necrosis factor-α (TNF-α). 14 immune cells exhibited significant causal relationships with attention deficit hyperactivity disorder (ADHD). CD3 on naive CD8br and CD4 on activated Treg were positively associated, while four CD27-expressing B cells were positively associated with ASD. Four CD40-expressing monocytes were negatively associated with ADHD. 7 inflammatory factors had significant causal relationships with ADHD: Fibroblast Growth Factor 23 levels (FGF-23), CD40L receptor levels, Glial Cell Line-Derived Neurotrophic Factor levels (GDNF), TNF-α were more important among these. Mediation analysis identified 12 mediating relationships, with three showing strong evidence: Natural killer cell receptor 2B4 levels (19.9%), FGF-23 (11%), and Eotaxin levels (- 5.95%). Strong causal relationships existed between immune cells, circulating inflammatory factors, and NDDs. Inflammatory factors mediated the pathways between immune cells and NDDs.

Parental kynurenine 3-monooxygenase genotype in mice directs sex-specific behavioral outcomes in offspring

BACKGROUND

Disruptions in brain development can impact behavioral traits and increase the risk of neurodevelopmental conditions such as autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and bipolar disorder, often in sex-specific ways. Dysregulation of the kynurenine pathway (KP) of tryptophan metabolism has been implicated in cognitive and neurodevelopmental disorders. Increased brain kynurenic acid (KYNA), a neuroactive metabolite implicated in cognition and sleep homeostasis, and variations in the Kmo gene, which encodes kynurenine 3-monooxygenase (KMO), have been identified in these patients. We hypothesize that parental Kmo genetics influence KP biochemistry, sleep behavior and brain energy demands, contributing to impairments in cognition and sleep in offspring through the influence of parental genotype and genetic nurture mechanisms.

METHODS

A mouse model of partial Kmo deficiency, Kmo heterozygous (HET-Kmo+/-), was used to examine brain KMO activity, KYNA levels, and sleep behavior in HET-Kmo+/- compared to wild-type control (WT-Control) mice. Brain mitochondrial respiration was assessed, and KP metabolites and corticosterone levels were measured in breast milk. Behavioral assessments were conducted on wild-type offspring from two parental groups: (i) WT-Control from WT-Control parents, (ii) wild-type Kmo (WT-Kmo+/+) from Kmo heterozygous parents (HET-Kmo+/-). All mice were C57Bl/6J background strain. Adult female and male offspring underwent behavioral testing for learning, memory, anxiety-like behavior and sleep-wake patterns.

RESULTS

HET-Kmo+/- mice exhibited reduced brain KMO activity, increased KYNA levels, and disrupted sleep architecture and electroencephalogram (EEG) power spectra. Mitochondrial respiration (Complex I and Complex II activity) and electron transport chain protein levels were impaired in the hippocampus of HET-Kmo+/- females. Breast milk from HET-Kmo+/- mothers increased kynurenine exposure during lactation but corticosterone levels were unchanged. Compared to WT-Control offspring, WT-Kmo+/+ females showed impaired spatial learning, heightened anxiety, reduced sleep and abnormal EEG spectral power. WT-Kmo+/+ males had deficits in reversal learning but no sleep disturbances or anxiety-like behaviors.

CONCLUSIONS

These findings suggest that Kmo deficiency impacts KP biochemistry, sleep behavior, and brain mitochondrial function. Even though WT-Kmo+/+ inherit identical genetic material as WT-Control, their development might be shaped by the parent's physiology, behavior, or metabolic state influenced by their Kmo genotype, leading to phenotypic sex-specific differences in offspring.

Association of Kawasaki disease with intellectual disability, attention deficit hyperactivity disorder, and autism spectrum disorder: a systematic review and meta-analysis

BACKGROUND

The relationship between Kawasaki disease (KD) and neurodevelopmental disorders (NDDs) remains unclear. This study aims to explore the association between them.

METHOD

A systematic review was conducted using PubMed and Embase databases from inception to May 1, 2024 (INPLASY202450017). We included case-control or cohort studies comparing KD patients to healthy controls in assessing attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability (ID). The meta-analysis employed a random-effects model to calculate effect sizes using hazard ratios (HRs) with 95% confidence intervals (CIs) for the disease occurrence. Moreover, mean differences (MDs) were used to calculate intelligence quotient (IQ).

RESULTS

Four eligible studies, including 1,454,499 participants, were analyzed for ADHD, ASD, and ID. The risk of ADHD in KD patients was higher than in healthy controls (HR[95%CI] = 1.76[1.21-2.57]). However, the risks of ASD (HR[95%CI] = 1.68[0.47-5.94]) and ID (HR[95%CI] = 1.39[0.52-2.63]) were not significantly different between KD and controls. Additionally, three studies with 365 participants were analyzed for IQ. IQ comparisons showed no significant differences in full IQ (MD[95%CI]=-0.01[-2.44-2.42]), verbal IQ (MD[95%CI]=-1.05[-4.42-2.33]), and performance IQ (MD[95%CI]=-0.08[-2.75-2.59]).

CONCLUSION

This study indicates that individuals with KD have a higher risk for ADHD but not for ASD or ID.

TRIAL REGISTRATION

INPLASY, INPLASY202450017. Registered 05 May 2024, https://inplasy.com/inplasy-2024-5-0017/ .

Alterations in Striatal Architecture and Biochemical Markers' Levels During Postnatal Development in the Rat Model of an Attention Deficit/Hyperactivity Disorder (ADHD)

Attention deficit/hyperactivity disorder (ADHD) is defined as a neurodevelopmental condition. The precise underlying mechanisms remain incompletely elucidated. A body of research suggests disruptions in both the cellular architecture and neuronal function within the brain regions of individuals with ADHD, coupled with disturbances in the biochemical parameters. This study seeks to evaluate the morphological characteristics with a volume measurement of the striatal regions and a neuron density assessment within the studied areas across different developmental stages in Spontaneously Hypertensive Rats (SHRs) and Wistar Kyoto Rats (WKYs). Furthermore, the investigation aims to scrutinize the levels and activities of specific markers related to immune function, oxidative stress, and metabolism within the striatum of juvenile and maturing SHRs compared to WKYs. The findings reveal that the most pronounced reductions in striatal volume occur during the juvenile stage in SHRs, alongside alterations in neuronal density within these brain regions compared to WKYs. Additionally, SHRs exhibit heightened levels and activities of various markers, including RAC-alpha serine/threonine-protein kinase (AKT-1), glucocorticoid receptor (GCsRβ), malondialdehyde (MDA), sulfhydryl groups (-SH), glucose (G), iron (Fe), lactate dehydrogenase (LDH). alanine transaminase (ALT), and aspartate transaminase (AST). In summary, notable changes in striatal morphology and elevated levels of inflammatory, oxidative, and metabolic markers within the striatum may be linked to the disrupted brain development and maturation observed in ADHD.

Differences in the Interleukin Profiles in Inattentive ADHD Prepubertal Children Are Probably Related to Conduct Disorder Comorbidity

Inflammatory cytokines are involved in attention deficit hyperactivity disorder (ADHD), a highly prevalent neurodevelopmental disorder. To quantify the baseline levels of pro- and anti-inflammatory cytokines and their changes after methylphenidate (MPH), a total of 31 prepubertal children with ADHD were recruited and subclassified into only two ADHD presentations-ADHD attention deficit (n = 13) or ADHD combined (n = 18). The children were also screened for oppositional defiant conduct disorder (ODCD) and anxiety disorder. Blood samples were drawn at 09:00 and after 4.63 ± 1.87 months of treatment. Four pro-inflammatory cytokines (interleukin-1beta (IL-1β), IL-5, IL-6, tumor necrosis factor-alpha (TNF-α)) and three anti-inflammatory cytokines (IL-4, IL-10, IL-13) were measured using a Luminex® assay. For statistics, a factorial analysis was performed in Stata 15.1. Overall, there were no statistically significant differences in the interleukin (IL) values induced by treatment. When grouped by presentation, the differences were present almost exclusively in ADHD-AD, usually with a profile opposite to that observed in ADHD-C, and with interactions between comorbid factors, with IL-1β (p = 0.01) and IL-13 (p = 0.006) being the ones reaching the greatest statistical significance. These differences are probably related to the ODCD factor, and they disappear after treatment. In conclusion, the changes observed in cytokine levels in prepubertal children only in the ADHD-AD presentation are probably related to comorbidities (specifically ODCD) and are mitigated after treatment.

Metabolomic Markers in Attention-Deficit/Hyperactivity Disorder (ADHD) among Children and Adolescents-A Systematic Review

Attention-Deficit/Hyperactivity Disorder (ADHD), characterized by clinical diversity, poses diagnostic challenges often reliant on subjective assessments. Metabolomics presents an objective approach, seeking biomarkers for precise diagnosis and targeted interventions. This review synthesizes existing metabolomic insights into ADHD, aiming to reveal biological mechanisms and diagnostic potentials. A thorough PubMed and Web of Knowledge search identified studies exploring blood/urine metabolites in ADHD-diagnosed or psychometrically assessed children and adolescents. Synthesis revealed intricate links between ADHD and altered amino acid metabolism, neurotransmitter dysregulation (especially dopamine and serotonin), oxidative stress, and the kynurenine pathway impacting neurotransmitter homeostasis. Sleep disturbance markers, notably in melatonin metabolism, and stress-induced kynurenine pathway activation emerged. Distinct metabolic signatures, notably in the kynurenine pathway, show promise as potential diagnostic markers. Despite limitations like participant heterogeneity, this review underscores the significance of integrated therapeutic approaches targeting amino acid metabolism, neurotransmitters, and stress pathways. While guiding future research, this overview of the metabolomic findings in ADHD suggests directions for precision diagnostics and personalized ADHD interventions.

Bifidobacterium animalis subsp. lactis A6 attenuates hippocampal damage and memory impairments in an ADHD rat model

Attention deficit hyperactivity disorder (ADHD) is commonly accompanied by learning and memory deficits. This study aimed to demonstrate the effects of probiotic Bifidobacterium animalis subsp. lactis A6 (BAA6) on behaviour and memory function in spontaneously hypertensive rats (SHRs). The results showed that BAA6 treatment ameliorated spatial working memory deficits and inhibited hippocampal neuron loss in SHRs. The levels of neurotransmitters such as acetylcholine, dopamine, and norepinephrine, and the brain derived neurotrophic factor increased and that of glutamate decreased in the brain tissue of SHRs after BAA6 administration. Moreover, BAA6 reduced the levels of pro-inflammatory cytokines TNF-α and IL-1β, and increased the levels of anti-inflammatory IL-10 and antioxidant glutathione in SHRs. 16S rRNA high-throughput sequencing showed that BAA6 treatment changed the gut microbiota composition. BAA6 promoted beneficial Lactobacillus, Romboutsia, Blautia, and Turicibacter, and decreased the enrichment of bacterial genera such as Dietzia, Sporosarcina, Brevibacterium, NK4A214_group, Atopostipes, and Facklamia negatively associated with neurotransmitter release and anti-inflammatory effects in SHRs. Together, these results suggested that BAA6 improved memory function by ameliorating hippocampal damage, abnormal neurotransmitter release and cerebral inflammation by reshaping the gut microbiota in SHRs. This study provides a scientific basis for the development and application of BAA6 as a promising dietary intervention to reduce the risk of ADHD.

The Kynurenine Pathway in Attention-Deficit/Hyperactivity Disorder: A Systematic Review and Meta-Analysis of Blood Concentrations of Tryptophan and Its Catabolites

Preliminary evidence shows that the kynurenine pathway (KP) may be altered in attention-deficit/hyperactivity disorder (ADHD). We thus conducted a systematic review and meta-analysis exploring the peripheral blood concentrations of tryptophan catabolites (TRYCATs) in people with ADHD. We searched the main electronic databases up to 7th December 2023. Standardised mean differences (SMDs) with 95% confidence intervals (95%CIs) were used to compare TRYCAT concentrations between participants with ADHD and healthy controls (HCs). We included eight studies. Random-effects meta-analyses found higher kynurenine (SMD = 0.56; 95%CI: 0.04 to 1.08; p = 0.033; I2 = 90.3%) and lower kynurenic acid (SMD = -0.33; 95%CI: -0.49 to -0.17; p < 0.001; I2 = 0%) concentrations in people with ADHD compared to HCs. Additional analyses on drug-free children with ADHD showed higher tryptophan (SMD = 0.31; 95%CI: 0.11 to 0.50; p = 0.002; I2 = 0%) and kynurenine (SMD = 0.74; 95%CI: 0.30 to 1.17; p < 0.001; I2 = 76.5%), as well as lower kynurenic acid (SMD = -0.37; 95%CI: -0.59 to -0.15; p < 0.001; I2 = 0%) blood levels, as compared to HCs. Despite some limitations, our work provides preliminary evidence on KP alterations in ADHD that may suggest decreased neuroprotection. Further research is needed to clarify the role of the KP in ADHD.

Inflammatory biotype of ADHD is linked to chronic stress: a data-driven analysis of the inflammatory proteome

The association between Attention Deficit Hyperactivity Disorder (ADHD) and low-grade inflammation has been explored in children but rarely in adults. Inflammation is characteristic of some, but not all, patients with ADHD and might be influenced by ADHD medication but also lifestyle factors including nutrition, smoking, and stress. It is also still unclear if any specific symptoms are related to inflammation. Therefore, we assessed 96 inflammatory proteins in a deeply phenotyped cohort of 126 adult ADHD participants with a stable medication status using OLINK technology. A data-based, unsupervised hierarchical clustering method could identify two distinct biotypes within the 126 ADHD participants based on their inflammatory profile: a higher inflammatory potential (HIP) and a lower inflammatory protein potential (LIP) group. Biological processes that differed strongest between groups were related to the NF-κB pathway, chemokine signaling, IL-17 signaling, metabolic alterations, and chemokine attraction. A comparison of sample characteristics revealed that the HIP group was more likely to have higher levels of chronic stress (p < 0.001), a higher clinical global impression scale score (p = 0.030), and a higher risk for suicide (p = 0.032). Medication status did not influence protein levels significantly (p ≥ 0.074), but psychotropic co-medication (p ≤ 0.009) did. In conclusion, our data suggest the presence of two distinct biotypes in adults with ADHD. Higher levels of inflammatory proteins in ADHD are linked to higher levels of chronic perceived stress in a linear fashion. Further research on inflammation in adults with ADHD should take stress levels into account.

S100B and Neuron-Specific Enolase Levels as Brain Injury Biomarkers in Internet Addiction: Effect of Sleep

BACKGROUND

Comorbidity of Internet addiction (IA) with sleep disruptions is common in adolescents. There is evidence that the levels of brain injury markers could be affected by sleep disruptions. In this study, we aimed to evaluate the relationship between sleep quality and these biomarkers within the framework of the relationship between IA and sleep disruptions.

METHODS

A total of 65 drug-free adolescents with newly diagnosed IA, aged 12 to 18 years, were included in the study, and they were divided into two groups considering the comorbidities of attention-deficit/hyperactivity disorder (ADHD) and social anxiety. The control group consisted of 30 healthy children. The participants were asked to complete the Young Internet Addiction Scale, Pittsburgh Sleep Quality Index (PSQI), Morningness Eveningness Questionnaire, Beck's Depression Inventory, Beck's Anxiety Inventory, and Barratt Impulsiveness Scale-11. Blood samples were taken between 8 and 9 am to analyze S100 calcium-binding protein B (S100B) and neuron-specific enolase (NSE) levels with enzyme-linked immunosorbent assay.

RESULTS

Plasma S100B and NSE levels were found to be statistically significantly higher in the IA with ADHD and the IA with anxiety groups than in healthy controls. NSE and S100B levels were found to be correlated with PSQI scores in both the IA groups. Also, there was a positive correlation between these biomarkers and IA severity.

CONCLUSIONS

Decreased sleep quality and daily sleep duration in IA might cause brain injury, resulting in an increase in the severity of the addiction. Prospective studies with large samples are needed to better explain the IA-sleep-brain injury relationship.

Neutrophil to lymphocyte ratio, platelet to lymphocyte ratio, and monocyte to lymphocyte ratio in ADHD: a systematic review and meta-analysis

Introduction

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with an unclear etiology. Systemic inflammation and immune dysregulation may play a role in the pathogenesis of ADHD. Morphology-derived parameters such as neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), and monocyte to lymphocyte ratio (MLR), have been proposed as peripheral biomarkers of the immune-inflammatory process in various diseases. However, studies examining their role in ADHD remain inconclusive.

Methods

A systematic review and a meta-analysis were conducted to evaluate the association between NLR, MLR, PLR and ADHD. Relevant articles were identified, screened, and assessed for quality according to PRISMA guidelines. Moreover, a qualitative and quantitative analyses were performed.

Results

The review contained eight eligible studies, five of which were included in the meta-analysis. The meta-analysis showed that ADHD patients had higher NLR and PLR values compared to health controls. No significant difference in MLR value was observed between the two groups. Analysis in relation to ADHD subtypes showed no significant differences in inflammatory markers in any of the included studies as well. The influence of medical treatment on these ratios could not be adequately assessed due to limited data.

Conclusion

ADHD patients exhibit higher NLR and PLR than healthy controls, which may indicate the potential immune-inflammatory involvement in this disorder. Further studies on inflammatory markers and ADHD, especially those considering the impact of treatment and clinical symptoms, are essential to comprehensively understand this association.

Comparison of Possible Changes in Oxidative Stress, DNA Damage, and Inflammatory Markers in Children/Adolescents Diagnosed with Sluggish Cognitive Tempo and Children/Adolescents Diagnosed with Attention-Deficit/Hyperactivity Disorder

Background: There has been a debate on whether sluggish cognitive tempo (SCT) differs from attention-deficit/hyperactivity disorder (ADHD). Although there have been many studies on metabolic parameters in relation to ADHD, no similar studies have been conducted on patients with SCT. We investigated whether there are differences between SCT and ADHD in terms of these factors. Subjects and Methods: Sixty-two participants with ages ranging from 11 to 18 who have diagnosis of ADHD (33 subjects) and SCT (29 subjects) were included in this study. The parents of all participants completed the 48-item Conners' Parent Rating Scale (CPRS) and the Barkley Child Attention Scale (BCAS) forms, and all participants' blood was taken to compare metabolic, oxidative stress, and antioxidant status of the SCT and ADHD groups. A child and adolescent psychiatrist interviewed the parents and children to assess the diagnosis of SCT and ADHD using standard diagnostic procedures. Results: In the comparison between the SCT and ADHD groups in terms of metabolic parameters, statistically significant differences were found in terms of total oxidant status, total antioxidant status, Oxidative Stress Index, total thiol, native thiol, disulfide, interleukin (IL)-1β, IL-6, and DNA damage (p < 0.05), but not in terms of tumor necrosis factor-α (p > 0.05). Conclusions: Our data showed that these two disorders may be different, but we believe that the data that indicate their differences remain inconclusive overall, but this study may be a potential pathway for future research.

Peripheral S100B Protein Levels in Five Major Psychiatric Disorders: A Systematic Review

Five major psychiatric disorders: schizophrenia, major depressive disorder, bipolar disorder, autistic spectrum disorder, and attention-deficit/hyperactivity disorder, show a shared genetic background and probably share common pathobiological mechanisms. S100B is a calcium-binding protein widely studied in psychiatric disorders as a potential biomarker. Our systematic review aimed to compare studies on peripheral S100B levels in five major psychiatric disorders with shared genetic backgrounds to reveal whether S100B alterations are disease-specific. EMBASE, Web of Science, and PubMed databases were searched for relevant studies published until the end of July 2023. This study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis Protocols (PRISMA) guidelines. Overall, 1215 publications were identified, of which 111 full-text articles were included in the systematic review. Study designs are very heterogeneous, performed mostly on small groups of participants at different stages of the disease (first-episode or chronic, drug-free or medicated, in the exacerbation of symptoms or in remission), and various clinical variables are analyzed. Published results are inconsistent; most reported elevated S100B levels across disorders included in the review. Alterations in S100B peripheral levels do not seem to be disease-specific.

Sex differences in vitamin D and behavioral profiles among children with allergic diseases

Previous studies have suggested that vitamin D has a protective effect on allergic diseases, while an individual's sex may have a moderating effect on the relationship between vitamin D and allergic-related immunity. This study aimed to determine the role of vitamin D in children with coexisting allergic diseases in the context of sex differences and to explore the behavioral profiles of these patients. We recruited a total of 103 children with atopic diseases and divided them into four groups: males with one allergic disease (MA1, n = 20), males with two or more allergic diseases (MA2, n = 26), females with one allergic disease (FA1, n = 30), and females with two or more allergic diseases (FA2, n = 27). We measured serum calcium levels using the colorimetric method and serum 25-OH vitamin D total levels using electrochemiluminescence immunoassay. We found that MA2 had significantly lower vitamin D levels than MA1 and FA2. The levels of IgE were negatively correlated with vitamin D in females, whereas the levels of IgE were not significantly correlated with vitamin D in males. Furthermore, serum IgE was significantly correlated with children's adaptive skills, and different sexes were associated with different aspects of adaptive skills. Our findings suggest a protective role of vitamin D in the development of one allergic disease against the coexistence of allergic diseases in males, as well as extend the evidence for sex differences in immunity by demonstrating a sex-different correlation between IgE and vitamin D and the relationship between IgE and children's adaptive skills.

Is S100B Involved in Attention-Deficit/Hyperactivity Disorder (ADHD)? Comparisons with Controls and Changes Following a Triple Therapy Containing Methylphenidate, Melatonin and ω-3 PUFAs

BACKGROUND

Increasing evidence supports a neuroinflammatory basis in ADHD damaging glial function and thereby altering dopaminergic (DA) neurotransmission. Previous studies focusing on the S100B protein as a marker of glial function have shown contradictory results. We conducted a clinical trial to investigate differences in S100B levels between ADHD patients and controls, as well as observe gradual changes in S100B concentrations after a triple therapy (TT) containing methylphenidate (MPH), melatonin (aMT) and omega-3 fatty acids (ω-3 PUFAs).

METHODS

62 medication-naïve children with ADHD (ADHD-G) and 65 healthy controls (C-G) were recruited. Serum S100B was measured at baseline (T0) in ADHD-G/C-G, and three (T3) and six months (T6) after starting TT in the ADHD-G, together with attention scores.

RESULTS

A significant increase in S100B was observed in the ADHD-G vs. C-G. In the ADHD-G, significantly higher S100B values were observed for comparisons between T0-T3 and between T0-T6, accompanied by a significant improvement in attention scores for the same timepoint comparisons. No significant differences were found for S100B between T3-T6.

CONCLUSION

Our results agree with the hypothesis of glial damage in ADHD. Further studies on the link between DA and S100B are required to explain the transient increase in S100B following TT.

Sex Differences in Neurodevelopmental Disorders: A Key Role for the Immune System

Sex differences are prominent defining features of neurodevelopmental disorders. Understanding the sex biases in these disorders can shed light on mechanisms leading to relative risk and resilience for the disorders, as well as more broadly advance our understanding of how sex differences may relate to brain development. The prevalence of neurodevelopmental disorders is increasing, and the two most common neurodevelopmental disorders, Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) exhibit male-biases in prevalence rates and sex differences in symptomology. While the causes of neurodevelopmental disorders and their sex differences remain to be fully understood, increasing evidence suggests that the immune system plays a critical role in shaping development. In this chapter we discuss sex differences in prevalence and symptomology of ASD and ADHD, review sexual differentiation and immune regulation of neurodevelopment, and discuss findings from human and rodent studies of immune dysregulation and perinatal immune perturbation as they relate to potential mechanisms underlying neurodevelopmental disorders. This chapter will give an overview of how understanding sex differences in neuroimmune function in the context of neurodevelopmental disorders could lend insight into their etiologies and better treatment strategies.

Chronic Pain and Psychiatric Conditions

Introduction

Chronic pain is a common condition with high socioeconomic and public health burden. A wide range of psychiatric conditions are often comorbid with chronic pain and chronic pain conditions, negatively impacting successful treatment of either condition. The psychiatric condition receiving most attention in the past with regard to chronic pain comorbidity has been major depressive disorder, despite the fact that many other psychiatric conditions also demonstrate epidemiological and genetic overlap with chronic pain. Further understanding potential mechanisms involved in psychiatric and chronic pain comorbidity could lead to new treatment strategies both for each type of disorder in isolation and in scenarios of comorbidity.

Methods

This article provides an overview of relationships between DSM-5 psychiatric diagnoses and chronic pain, with particular focus on PTSD, ADHD, and BPD, disorders which are less commonly studied in conjunction with chronic pain. We also discuss potential mechanisms that may drive comorbidity, and present new findings on the genetic overlap of chronic pain and ADHD, and chronic pain and BPD using linkage disequilibrium score regression analyses.

Results

Almost all psychiatric conditions listed in the DSM-5 are associated with increased rates of chronic pain. ADHD and BPD are significantly genetically correlated with chronic pain. Psychiatric conditions aside from major depression are often under-researched with respect to their relationship with chronic pain.

Conclusion

Further understanding relationships between psychiatric conditions other than major depression (such as ADHD, BPD, and PTSD as exemplified here) and chronic pain can positively impact understanding of these disorders, and treatment of both psychiatric conditions and chronic pain.

A Potential Role for Neuroinflammation in ADHD

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioural disorder in children and adolescents. Although increases in oxidative stress and disturbances of neurotransmitter system such as the dopaminergic and abnormalities in several brain regions have been demonstrated, the pathophysiology of ADHD is not fully understood. Nevertheless, ADHD involves several factors that have been associated with an increase in neuroinflammation. This chapter presents an overview of factors that may increase neuroinflammation and play a potential role in the development and pathophysiology of ADHD. The altered immune response, polymorphisms in inflammatory-related genes, ADHD comorbidity with autoimmune and inflammatory disorders and prenatal exposure to inflammation are associated with alterations in offspring brain development and are a risk factor; genetic and environmental risk factors that may increase the risk for ADHD and medications can increase neuroinflammation. Evidence of an association between these factors has been an invaluable tool for research on inflammation in ADHD. Therefore, evidence studies have made it possible to generate alternative therapeutic interventions using natural products as anti-inflammatories that could have great potential against neuroinflammation in ADHD.

Potential Inflammatory Biomarker in Patients with Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder that can diminish the quality of life of both children and adults in academic, occupational, and social contexts. The kynurenine pathway (KP) contains a set of enzymatic reactions involved in tryptophan (TRP) degradation. It is known to be associated with the risk of developing ADHD. This review will address the KP and underlying mechanism of inflammation in ADHD. Potential inflammatory biomarkers reported in the most recent studies are summarized. Although a strong neuroimmunological basis has been established due to the advances of recent neurobiological research, the pathophysiology of ADHD remains unclear.

Effect of vitamin D supplementation on brain waves, behavioral performance, nitric oxide, malondialdehyde, and high-sensitivity C-reactive protein in children with attention deficit/hyperactivity disorder: study protocol for a randomized clinical trial

Background

Attention deficit/hyperactivity disorder (ADHD) is the most common chronic mental and behavioral disorder among children. Some studies showed the lower levels of vitamin D in patients with ADHD compared with the healthy people. Few clinical trials were conducted in this field. The present study will be performed to examine the effect of vitamin D supplementation in children with ADHD.

Methods

We will conduct a double-blind, randomized controlled clinical trial to investigate the effect of vitamin D supplementation on brain waves, behavioral performance, serum nitric oxide, malondialdehyde, and high-sensitivity C-reactive protein in 50 patients with ADHD. The intervention group will receive one capsule 50,000 IU vitamin D every week, for 8 weeks. The control group will receive one placebo capsule containing 1000 mg olive oil every week. Electroencephalography will be performed for 10 min using Brain Master Discovery from 19 scalp sites both before the first intervention and the 10 sessions of the therapy. The artifact-free periods of 1-min electroencephalography data will be analyzed for quantitative electroencephalography measures.

Discussion

For the first time, this clinical trial will evaluate the effect of vitamin D supplementation on brain waves, serum nitric oxide, malondialdehyde, and high-sensitivity C-reactive protein in patients with ADHD. The results of the present clinical trial will provide a better vision about the vitamin D efficacy in patients with ADHD.

Trial registration

Registered on 5 November 2020 at Iranian Registry of Clinical Trials with code number IRCT20200922048802N1 (https://www.irct.ir/trial/51410).

The relationship between central fatigue and Attention Deficit/Hyperactivity Disorder of the inattentive type

Chronic fatigue and central fatigue with malaise significantly impair quality of life. Inattention caused by central fatigue is closely related to attention deficit/hyperactivity disorder (ADHD) symptoms, but the neurochemical mechanism of central fatigue remains hypothetical. The serotonin hypothesis of central fatigue was proposed first, serving as the central dogma for the molecular and neural mechanisms of central fatigue, and underpinning many studies. The tryptophan hypothesis was proposed because tryptophan released into the synaptic cleft of neurons in the brain coincides with and responds sensitively to development of fatigue. Tryptophan is highly bioactive, with brain concentrations of 50 to 200 times that of serotonin. The tryptophan-kynurenic acid-synergy hypothesis posits that central fatigue is not monocausal but a synergistic effect between tryptophan itself and its catabolite kynurenic acid. Central fatigue is associated with mental health problems and is a cause of inattention, thereby warranting scrutiny for its relationship with ADHD. Fatigability in ADHD is mediated by tryptophan, in which abnormal enhancement of the tryptophan-kynurenine-kynurenic acid pathway causes an imbalance in monoamine nervous system function. Notably, noradrenergic neuronal dysfunction is associated with the characteristic inattention of ADHD. Neutral amino acids such as branched-chain amino acids (BCAAs) can assist recovery from attentional and cognitive decline caused by central fatigue. Since they are transported by the same L-amino acid transporter as tryptophan, BCAAs compete with tryptophan to inhibit its brain uptake. Controlling central fatigue this way may improve attentional cognitive performance.

Sex-specific relationships of the infant microbiome and early-childhood behavioral outcomes

BACKGROUND

A link between the gut microbiome and behavior is hypothesized, but most previous studies are cross-sectional or in animal models. The modifying role of host sex is poorly characterized. We aimed to identify sex-specific prospective associations between the early-life gut microbiome and preschool-age neurobehavior.

METHODS

In a prospective cohort, gut microbiome diversity and taxa were estimated with 16S rRNA sequencing at 6 weeks, 1 year, and 2 years. Species and gene pathways were inferred from metagenomic sequencing at 6 weeks and 1 year. When subjects were 3 years old, parents completed the Behavioral Assessment System for Children, second edition (BASC-2). A total of 260 children contributed 523 16S rRNA and 234 metagenomics samples to analysis. Models adjusted for sociodemographic characteristics.

RESULTS

Higher diversity at 6 weeks was associated with better internalizing problems among boys, but not girls [βBoys = -1.86 points/SD Shannon diversity; 95% CI (-3.29, -0.42), pBoys = 0.01, βGirls = 0.22 (-1.43, 1.87), pGirls = 0.8, pinteraction = 0.06]. Among other taxa-specific associations, Bifidobacterium at 6 weeks was associated with Adaptive Skills scores in a sex-specific manner. We observed relationships between functional features and BASC-2 scores, including vitamin B6 biosynthesis pathways and better Depression scores.

CONCLUSIONS

This study advances our understanding of microbe-host interactions with implications for childhood behavioral health.

IMPACT

This is one of the first studies to examine the early-life microbiome and neurobehavior, and the first to examine prospective sex-specific associations. Infant and early-childhood microbiomes relate to neurobehavior including anxiety, depression, hyperactivity, and social behaviors in a time- and sex-specific manner. Our findings suggest future studies should evaluate whether host sex impacts the relationship between the gut microbiome and behavioral health outcomes.

Cytokine Levels and Neuropsychological Function among Patients with Attention-Deficit/Hyperactivity Disorder and Atopic Diseases

Since atopic disease and inflammatory cytokines are both involved in attention deficit hyperactivity disorder (ADHD), in this study, we examined the relationship among cytokine levels, neuropsychological function, and behavioral manifestations in patients with ADHD and atopic diseases. Participants were categorized into individuals with ADHD and atopic disease (n = 41), those with ADHD without allergy (n = 74), individuals without ADHD but with allergy (n = 23), and those without ADHD or allergy (n = 49). We used the Swanson, Nolan, and Pelham IV Scale (SNAP-IV), Conners’ Continuous Performance Test (Conners CPT), and Conners’ Continuous Auditory Test of Attention (CATA) to assess patients’ behavioral symptoms, visual attention, and auditory attention, respectively. Participants’ IFN-γ, IL-1B, IL-6, IL-10, IL-13, IL-17, MCP-1, and TNF-α plasma levels were assessed using multiplex assays. We found that the prevalence rates of atopic diseases (asthma, allergic rhinitis, or atopic dermatitis) were similar between individuals with ADHD and those without ADHD. ADHD behavioral symptoms (SNAP-IV), CPT omission scores, and CATA detectability scores demonstrated significant differences between individuals with ADHD and those without ADHD, regardless of atopic diseases. However, plasma levels of cytokines (TNF-α, IFN-γ, and IL-17) were negatively correlated with inattention symptoms. This study demonstrates a potential relationship between cytokine levels and neuropsychological function among patients with ADHD and atopic diseases.

Association between cord blood metabolites in tryptophan pathway and childhood risk of autism spectrum disorder and attention-deficit hyperactivity disorder

Alterations in tryptophan and serotonin have been implicated in various mental disorders; but studies are limited on child neurodevelopmental disabilities such as autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). This prospective cohort study examined the associations between levels of tryptophan and select metabolites (5-methoxytryptophol (5-MTX), 5-hydroxytryptophan (5-HTP), serotonin, N-acetyltrytophan) in cord plasma (collected at birth) and physician-diagnosed ASD, ADHD and other developmental disabilities (DD) in childhood. The study sample (n = 996) derived from the Boston Birth Cohort, which included 326 neurotypical children, 87 ASD, 269 ADHD, and 314 other DD children (mutually exclusive). These participants were enrolled at birth and followed-up prospectively (from October 1, 1998 to June 30, 2018) at the Boston Medical Center. Higher levels of cord 5-MTX was associated with a lower risk of ASD (aOR: 0.56, 95% CI: 0.41, 0.77) and ADHD (aOR: 0.79, 95% CI: 0.65, 0.96) per Z-score increase, after adjusting for potential confounders. Similarly, children with cord 5-MTX ≥ 25th percentile (vs. <25th percentile) had a reduction in ASD (aOR: 0.27, 95% CI: 0.14, 0.49) and ADHD risks (aOR: 0.45, 95% CI: 0.29, 0.70). In contrast, higher levels of cord tryptophan, 5-HTP and N-acetyltryptophan were associated with higher risk of ADHD, with aOR: 1.25, 95% CI: 1.03, 1.51; aOR: 1.32, 95% CI: 1.08, 1.61; and aOR: 1.27, 95% CI: 1.05, 1.53, respectively, but not with ASD and other DD. Cord serotonin was not associated with ASD, ADHD, and other DD. Most findings remained statistically significant in the sensitivity and subgroup analyses.

The Influence of Lactobacillus paracasei HII01 Supplementation on Performance in Attention (Go/No-Go) Tasks and Quinolinic Acid and 5-Hydroxyindoleacetic Acid Levels in Thai Children—A Preliminary Study

Cognitive development is defined as the capacity of a child to think, reason, and use language, which are all vital to their overall growth. Attention deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder. Though several factors are associated with the incidence of ADHD, gut microbiota and gut homeostasis play critical roles in it. Gut dysbiosis and altered gut homeostasis are linked to several physical and psychological complications that affect gut–brain communication (the gut–brain axis). Probiotics, live microorganisms that confer a health benefit to the host when administered in adequate amounts, are considered therapeutic supplements that can be used to manage mental and cognitive disorders. Intervention with probiotics can improve the gut microbial ecosystem and the gut–brain axis, thereby improving cognitive function. We hypothesized that the supplementation of Lactobacillus paracasei HII01 might reduce the risk of the development of neuropsychiatric disorders; thus, we evaluated the efficacy of L. paracasei HII01 on the attention state of healthy children and the changes in representative neuroinflammatory markers. Ten healthy Thai children were supplemented with 109 CFU of L. paracasei HII01 for 12 weeks. Go/no-go tasks were undertaken to assess changes in attention state. Alterations in brain waves were measured by electroencephalographic (EEG)/event-related potential (ERP) recordings. The levels of quinolinic acid (QA, a metabolite of tryptophan) and 5-hydroxyindoleacetic acid (5-HIAA, a metabolite of serotonin) were determined in the urine at baseline and after 12 weeks of probiotic intervention. The levels of QA and 5-HIAA significantly decreased and increased, respectively. The QA/5-HIAA ratio also decreased significantly. Go/No-go tasks revealed that the percentages of go accuracy and go error increased and decreased significantly, respectively. EEG/ERP recordings showed that theta, alpha, and beta waves were substantially altered at the 12th week of study compared to baseline values. The results suggested that L. paracasei HII01 might improve the gut microbiota and oscillate the brain function, which sustained the attention state of the subjects. These preliminary findings require further detailed study to confirm the role of L. paracasei HII01 in the improvement in the attention of healthy children.

New Hematological Parameters as Inflammatory Biomarkers: Systemic Immune Inflammation Index, Platerethritis, and Platelet Distribution Width in Patients with Adult Attention Deficit Hyperactivity Disorder

OBJECTIVES

The potential role of neuroinflammation in adult attention deficit hyperactivity disorder (ADHD) patients has been investigated with peripheral hemogram-related inflammatory markers. Systemic immune inflammation index (SII) is defined as a new index that has been developed for the balance of inflammatory and immune status.

METHODS

Our study was based on a prospective routine complete blood count(CBC) analysis of 74 Adult ADHD patients and 70 healthy participants. The DSM-5-Clinician version and Barratt impulsivity scale-11 were used to evaluate the participants.

RESULTS

There was no statistical difference in the comparison of the SII ratios, platelet distribution width (PDW), and plateretritis (PCT) (p>0.05 for each) in a group of a young adults with ADHD and in a comparison control group. These inflammatory indicators were found to be similar between patients newly diagnosed with ADHD (n=40) and patients using methylphenidate (n=34) (p>0.05 for each). The relationship between ADHD clinical symptoms and severity and inflammation was evaluated. A significant negative correlation was observed between attention deficit scores and PCT (r=-0.301, p=0.009). A positive significant correlation was found between hyperactivity scores and SII (r=0.247, p=0.034). A significant positive correlation was found between Barrat motor scores and PDW(r=241, p=0.038). In the regression analysis, the PCT variable changed the attention deficit variable (β=.33, t(70)= -2.703, p=.009, pr ²= .094) predicted negatively and significantly.

CONCLUSIONS

We demonstrated the association of SII, which is independently associated with adverse outcomes in many diseases, and the severity of hyperactivity symptoms in adult ADHD. The fact that PCT predicts attention deficit negatively and decisively shows the importance of inflammatory assessments specific to clinical presentations. The critical importance of platelets in inflammatory processes in ADHD has been demonstrated once again with inflammatory markers such as SII, PLT, and PDW, which can be accessed by an easily applicable complete blood count method.

Dietary phytochemical index and attention-deficit/hyperactivity disorder in Iranian children: a case control study

OBJECTIVE

Attention Deficit/Hyperactivity Disorder (ADHD) is a common behavioral disorder among children. Based on literature, it has been hypothesized that the higher intake of rich sources of phytochemicals may be inversely related to the risk of ADHD. We investigated the association of dietary phytochemical index (DPI) with odds of ADHD.

METHODS

This case-control study was conducted on 360 children and adolescents 7-13 years old in Yazd, Iran. Subjects were categorized into the case (n = 120) and control groups (n = 240) based on matching age and sex. To diagnose ADHD, the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSMIV-TR) was used. Food frequency questionnaire was used to measure food intake. DPI was calculated by percent of daily energy intake from phytochemical-rich foods. The association of DPI with the odds ratio of ADHD was examined by logistic regression.

RESULTS

Subjects in the highest quartile of DPI have higher intake of macronutrient, eicosatetraenoic acid, docosahexaenoic acid, calcium, zinc, iron, vitamins B12, B6, and folic acid compared to lowest quartile. After adjusting for potential confounders, subjects in the highest quartile of DPI compared with subjects in the lowest quartile showed a lower risk of ADHD (OR: 0.44; 95% CI: 0.18-0.90). There was a significant decreasing trend in the odds of ADHD across increasing quartile of DPI (P for trend: 0.02).

CONCLUSION

We found that higher DPI score is associated with lower risk of ADHD in children. Cohort and clinical studies are necessary to approve our results.

A New Perspective of Attention Deficit Hyperactivity Disorder Associated With Delayed Language Development: An Egyptian Sample

OBJECTIVE

The current study aimed to get an easy objective method to detect attention deficit hyperactivity disorder (ADHD) by investigating the simple inflammatory blood ratios platelet/lymphocyte ratio (PRL), neutrophil/lymphocyte ratio (NLR) & the monocyte/lymphocyte ratio (MLR), for the sake of receiving early management to such cases and overcoming language affection as a comorbid symptom.

METHODS

This study was conducted on two groups: Group 1 (SG) consisted of 70 ADHD children who had delayed language development (DLD), freshly diagnosed, according to DSM-V criteria, and those patients were not on medical treatment. Group 2 healthy group (HG) consisted of 44 healthy control normal children that were both physically and mentally free of the same socio-demographic characters of the first group.

RESULTS

The PLR, NLR and MLR, were significantly higher in the ADHD group than the healthy control group (HG) group, although the simple blood indices were average.

CONCLUSION

Inflammation has a role as a comorbid cause of ADHD. Simple blood inflammatory mediators may be used as comorbid factors in ADHD. This study explained that the language abilities must be taken in consideration when assessing children with ADHD. The screening tools for inflammatory markers are important when dealing with ADHD children with/ without delayed language development (DLD). Also, working memory assessment is mandatory in ADHD with DLD to assign a special program in language therapy for each child.

Neurological and neurodevelopmental symptoms in children with familial Mediterranean fever and their siblings

Familial Mediterranean fever is a common autoinflammatory disease characterized by periodic attacks of fever and serositis. There are few reports describing neurological symptoms in patients with FMF. The aim of this study was to systematically assess the neurologic and developmental involvement in pediatric patients with FMF. Between the years 2016 and 2019, parents of children with FMF were asked to complete a questionnaire regarding the presence of neurological and developmental symptoms in their children with and without FMF. Demographic data, clinical characteristics, and disease course of FMF patients were collected from the medical charts. Neurodevelopmental manifestations were compared between the children with FMF and their siblings. A total of 205 children were enrolled (11.6 ± 4.7 years of age): 111 children with FMF and 94 healthy siblings in the control group. Neurological morbidity was frequently reported in children with FMF: 44 (40%) had recurrent headaches, 31 (28%) ADHD symptoms, 27 (24%) learning disabilities, and 10 (9%) febrile convulsions. Headaches and febrile convulsions were significantly more prevalent in children with FMF as compared to their siblings (ps < 0.05). ADHD and learning disabilities were associated with poor adherence to colchicine treatment.Conslusions: The present study found an increased prevalence of ADHD, learning disabilities, headaches, and febrile seizures in children with FMF. The findings underscore the importance of addressing the neurodevelopmental domain in children with FMF. In addition, detection and treatment of ADHD and learning disabilities could improve adherence with therapy and control of the underlying disease. What is Known: • Familial Mediterranean fever (FMF) is the most common inherited auto-inflammatory disease, characterized by recurrent attacks of fever, serositis, and arthritis. • Some previous case reports also described rare neurological manifestations in children with FMF. What is New: • The study found an increased prevalence of headaches, febrile seizures, ADHD, and learning disabilities, in children with FMF. • The findings underscore the importance of addressing the neurological domain in this population, which could potentially improve adherence with therapy and control of the underlying disease.

Increased Serum Level of CCL5 in Children with Attention‑Deficit/Hyperactivity Disorder: First Results about Serum Chemokines

Objective

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder and its aetiology is not fully understood. This study aimed to determine whether the CCL5 and CCL11 influence the ADHD aetiology by comparing serum CCL5 and CCL11 levels of children with ADHD and typical development.

Methods

This study included 45 (27 males, mean age = 8.9 ± 1.7 years) treatment-naive patients diagnosed with ADHD and 35 (20 males, mean age = 8.8 ± 1.6 years) healthy controls. Participants ranged in age between 6−12 years and completed the Conners Teacher Rating Scale that assesses ADHD presentation and severity. CCL5 and CCL11 serum levels were also measured using enzyme-linked immunosorbent assay kits.

Results

Significantly higher serum CCL5 levels were found in children with ADHD compared to healthy controls (p < 0.001). No significant difference was found between the mean serum CC11 level of the patients and controls (p = 0.93). In addition, there was no significant correlation between the serum CCL5 and CCL11 levels and predominant presentations of ADHD and disease severity.

Conclusion

This study suggests that there are higher levels of serum CCL5 in drug naive children with ADHD, this findings suggest that CCL5 might play a role in the pathophysiology of ADHD. Moreover, these changes in peripheral blood may have therapeutic value. In addition, these results help to understand the role of chemokines in elucidating the etiopathogenesis of ADHD. Our results can be considered as the first step in investigating the role of CCL5 in ADHD, and further research is needed to support these initial findings.

Gut microbiota and plasma cytokine levels in patients with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common childhood mental disorder with undetermined pathophysiological mechanisms. The gut microbiota and immunological dysfunction may influence brain functions and social behaviours. In the current study, we aimed to explore the correlation of gut microbiome imbalance and inflammation in the pathophysiology of ADHD. Forty-one children with ADHD and thirty-nine healthy-control (HC) individuals were recruited. Faecal samples from all participants were collected and submitted for 16 S rRNA V3-V4 amplicon microbiome sequencing analysis. The plasma levels of 10 cytokines, including TNF-α, IL-6, IL-1β, IL-2, IL-10, IL-13, IL-17A, IFN-α2, IFN-γ, and MCP-1, were determined using a custom-made sandwich enzyme-linked immunosorbent assay (ELISA) developed by Luminex Flowmetrix. There was no significant difference between the ADHD and HC groups in species diversity in the faeces, as determined with α-diversity and β-diversity analysis. In the ADHD group, three differentially abundant taxonomic clades at the genus level were observed, namely Agathobacter, Anaerostipes, and Lachnospiraceae. Top differentially abundant bacteria and representative biological pathways were identified in children with ADHD using linear discriminant analysis (LDA) effect size (LEfSe), and the phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis, respectively. The plasma levels of TNF-α were significantly lower in children with ADHD than in HCs. Within the ADHD group, the levels of TNF-α were negatively correlated with ADHD symptoms and diversity of the gut microbiome. Our study provides new insights into the association between gut microbiome dysbiosis and immune dysregulation, which may contribute to the pathophysiology of ADHD.

Influence of the inflammasome complex on psychiatric disorders: clinical and preclinical studies

INTRODUCTION

The innate immune complex, an inflammasome complex, has a role in the etiology of psychiatric disorders. Preclinical studies have demonstrated that the inflammasome activation leads to psychiatric disorders and clinical studies have proved that specific psychiatric illnesses are associated with aberrant levels of inflammatory cytokines and inflammasome. The inflammasome complex could be a major factor in the progression and pathology of psychiatric disorders.

AREA COVERED

We discuss the pathogenesis of psychiatric disorders with respect to the activation of the inflammasome complex. Inflammasome-associated inflammatory cytokines are observed in patients and animal models of psychiatric disorders. The article also reflects on inflammasome regulatory options for the prevention and treatment of psychiatric disorders. Relevant literature available on PubMed from 1992 to 2021 has been included in this review.

EXPERT OPINION

Modulating the inflammasome complex is a potential therapeutic strategy to treat symptom severity for patients with psychiatric disorders, particularly those with inflammasome-associated disorders. However, the nature of the psychiatric disorders should be considered when targeting inflammasome.

Non-mental diseases associated with ADHD across the lifespan: Fidgety Philipp and Pippi Longstocking at risk of multimorbidity?

Several non-mental diseases seem to be associated with an increased risk of ADHD and ADHD seems to be associated with increased risk for non-mental diseases. The underlying trajectories leading to such brain-body co-occurrences are often unclear - are there direct causal relationships from one disorder to the other, or does the sharing of genetic and/or environmental risk factors lead to their occurring together more frequently or both? Our goal with this narrative review was to provide a conceptual synthesis of the associations between ADHD and non-mental disease across the lifespan. We discuss potential shared pathologic mechanisms, genetic background and treatments in co-occurring diseases. For those co-occurrences for which published studies with sufficient sample sizes exist, meta-analyses have been published by others and we discuss those in detail. We conclude that non-mental diseases are common in ADHD and vice versa and add to the disease burden of the patient across the lifespan. Insufficient attention to such co-occurring conditions may result in missed diagnoses and suboptimal treatment in the affected individuals.

Alterations of kynurenine pathway in alcohol use disorder and abstinence: a link with gut microbiota, peripheral inflammation and psychological symptoms

The gut-brain communication is mostly driven by the immune, metabolic and neural pathways which remained poorly explored in patients with alcohol use disorder (AUD). The metabolites arising from the tryptophan-kynurenine pathway have gained considerable attention since they are at the interface between intestinal bacteria, host immune response and brain functions. This study described the circulating levels of kynurenine metabolites in AUD patients, at the onset (T1) and end (T2) of a 3-week detoxification program, and tested correlations between those metabolites and inflammatory markers, the gut microbiota and the psychological symptoms. Increased concentration of the neurotoxic metabolite quinolinic acid (QUIN) and decreased levels of the neuroprotector metabolite kynurenic acid (KYNA) which both modulate glutamatergic neurotransmission were observed in AUD patients, particularly at T2. The inflammatory marker hsCRP was associated with several metabolic ratios of the kynurenine pathway. Tryptophan, KYNA and QUIN were correlated with depression, alcohol craving and reaction time, respectively. Analysis of gut microbiota revealed that bacteria known as short-chain fatty acid producers, as well as bacterial metabolites including butyrate and medium-chain fatty acids were associated with some metabolites of the tryptophan-kynurenine pathway. Targeting the glutamatergic neurotransmission through the modulation of the kynurenine pathway, by manipulating the gut microbiota, might represent an interesting alternative for modulating alcohol-related behavior.

Personalised medicine in child and Adolescent Psychiatry: Focus on omega-3 polyunsaturated fatty acids and ADHD

Attention deficit hyperactivity disorder, or ADHD, is a common childhood disorder with a prevalence rate of 5–10%. There have been many theories proposed to explain ADHD, and one of them focuses on the deficiency of essential fatty acids (EFA), particularly omega-3 polyunsaturated fatty acids (n-3 PUFAs) including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Studies have shown that there is a positive correlation between EFA deficiency severity and ADHD symptoms, and a negative association between blood PUFAs levels and ADHD symptoms. Moreover, clinical studies have shown a promising effect of n-3 PUFAs in the treatment of both clinical and cognitive symptoms in children with ADHD. In addition, with the more relatively safe and tolerable properties of n-3 PUFAs when comparing with the standard pharmacotherapy, n-3 PUFAs may be a potential treatment option for children with ADHD. Of note, the association between n-3 PUFAs deficiency and ADHD has been suggested to involve several biological systems, including inflammation, dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS), and an imbalanced gut-microbiota axis (GBA). Thus, the biomarkers from these biological systems may serve as possible treatment response predictors of n-3 PUFAs in children with ADHD.

•

Children with ADHD have lower levels of DHA, EPA and total n-3 PUFAs

•N-3 PUFAs improved clinical and cognitive symptoms in children with ADHD

•Inflammatory status and endogenous n-3 PUFAs levels may serve as treatment response predictors

•N-3 PUFAs may be a treatment option for a subgroup of children with ADHD

Methylphenidate ameliorates the homeostatic balance between levels of kynurenines in ADHD children

The kynurenine pathway of tryptophan metabolism has been involved in ADHD We quantified basal levels and daily fluctuations of tryptophan and several kynurenine metabolites, as well as their changes after treatment with methylphenidate (MPH). A total of 179 children were recruited, grouped into ADHD (n = 130) and healthy controls (CG,n = 49). Blood samples were drawn at 20:00 and 09:00 h and only in the ADHD group after 4.63±2.3 months of treatment. Nocturnal urine was collected between both draws. Factorial analysis (Stata12.0) was performed with Groups, Time, Hour of Day and Depressive Symptoms (DS) as factors. MPH significantly increased plasma Kynurenic acid (2.4 ± 1.03/2.78±1.3 ng/mL; baseline/post-treatment, morning; z = 1.96,p<0.05) and Xanthurenic acid (2.39±0.95/2.88±1.19 ng/mL; baseline/post, morning; z = 2.7,p<0.007) levels, both with higher values in the evening. In DS+ patients, MPH caused a pronounced decrease in evening Anthranilic acid [3.08±5.02/ 1.82±1.46 ng/mL, z = 2.68,p = 0.0074] until matching values to other subgroups. In urine, MPH decreased the excretion of both Nicotinamide and Quinolinic acids, but only in the DS- subgroup. The kynurenine pathway may participate in the highly clinical favorable response to MPH. The observed changes could be considered as protective (i.e. increased plasma kynurenic acid vs. decreased quinolinic acid excretion) based on the knowledge of its physiological homeostatic functions.

In vivo imaging of dopamine D1 receptor and activated microglia in attention-deficit/hyperactivity disorder: a positron emission tomography study

Alterations in the cortical dopamine system and microglial activation have been implicated in the pathophysiology of attention-deficit/hyperactivity disorder (ADHD), one of neurodevelopmental disorders that can be conventionally treated with a dopamine enhancer (methylphenidate) albeit unsatisfactorily. Here, we investigated the contributions of the dopamine D1 receptor (D1R) and activated microglia and their interactions to the clinical severities in ADHD individuals using positron emission tomography (PET). Twenty-four psychotropic-naïve ADHD individuals and 24 age- and sex-matched typically developing (TD) subjects underwent PET measurements with [¹¹C]SCH23390 for the D1R and [¹¹C](R)PK11195 for activated microglia as well as assessments of clinical symptoms and cognitive functions. The ADHD individuals showed decreased D1R in the anterior cingulate cortex (ACC) and increased activated microglia in the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) compared with the TD subjects. The decreased D1R in the ACC was associated with severe hyperactivity in the participants with ADHD. Microglial activation in the DLPFC were associated with deficits in processing speed and attentional ability, and that in the OFC was correlated with lower processing speed in the ADHD individuals. Furthermore, positive correlations between the D1R and activated microglia in both the DLPFC and the OFC were found to be significantly specific to the ADHD group and not to the TD group. The current findings suggest that microglial activation and the D1R reduction as well as their aberrant interactions underpin the neurophysiological mechanism of ADHD and indicate these biomolecular changes as a novel therapeutic target.

Cortisol and inflammatory biomarker levels in youths with attention deficit hyperactivity disorder (ADHD): evidence from a systematic review with meta-analysis

Several studies reported abnormal cortisol and inflammatory biomarker levels in youths with attention deficit hyperactivity disorder (ADHD), but the results have not been conclusive. We conducted a systematic review followed by a meta-analysis of case-control studies assessing blood or saliva cortisol levels and blood levels of inflammatory biomarkers in youth with ADHD. The effect sizes (ES) were synthesized by using a random-effects model. In the 19 studies on cortisol levels (totaling n = 916 youth with ADHD and n = 947 typically developing (TD), healthy youth), youth with ADHD have lower basal cortisol levels at any time-points during the day (effect size: .68; p = 0.004) and lower cumulative levels of cortisol (ES: .39, p = .008) throughout the day than TD youth. Moreover, morning cortisol levels were lower in ADHD youth when compared with TD youth (14 studies, n = 1679, ES: .84, p = 0.003), while there is no difference for the afternoon cortisol levels (p = 0.48). The meta-analysis on inflammation biomarker was conducted on 4 studies (totaling n = 404 youth) showed that Tumour Necrosis Factor-alpha (TNF-α) was lower in ADHD when compared with TD (3 studies, n = 257 youth, p = 0.004), while no differences for Interleukin-1β(IL-1β) (p = 0.21), IL-6 (p = 0.09) and IL-10 (p = 0.77). The lower cortisol in the context of low TNF-α levels may indicate a specific pattern of biomarkers in ADHD, and further investigation is warranted.

Review: Inflammation and anxiety-based disorders in children and adolescents - a systematic review and meta-analysis

BACKGROUND

Anxiety-based disorders are common and are often chronic with an onset during childhood or adolescence. An emerging literature has examined the role of inflammation in these disorders by measuring blood concentrations of inflammatory markers such as cytokines, C-reactive protein (CRP) and immune markers such as white blood cell counts. However, existing results are inconsistent, with available meta-analyses only including adult populations. We believe this is the first systematic review and meta-analysis to investigate these inconsistencies among the population of children and adolescents.

METHODS

A systematic search of five electronic databases was conducted to identify studies which compared inflammatory markers between individuals with an anxiety-based disorder and healthy controls. Study quality was assessed, and pooled effect sizes (Hedges' g) were calculated using random-effects meta-analyses.

RESULTS

Nine independent studies were identified. The combined meta-analysis of 16 cytokines and CRP was approaching significance; however, no significant between-group difference was observed for meta-analyses of individual inflammatory or immune markers. Heterogeneity was high, and quality assessments identified important limitations; primarily, small sample sizes and a lack of control over confounding variables.

CONCLUSIONS

Although no significant effects were observed, the small number of included studies and limitations in study or reporting quality render these findings provisional. Research in this area has the potential for important clinical implications in relation to therapeutic interventions. Important recommendations for further research are put forth.

The role of tryptophan metabolic pathway in children with attention deficit hyperactivity disorder with and without comorbid oppositional defiant disorder and conduct disorder

Accumulating data presented that tryptophan metabolic pathway (TMP) may play a role in attention-deficit/hyperactivity disorder (ADHD). However, no study have investigated potential role of TMP in disruptive behavior disorders coexisting with ADHD. This study compared serum levels of tryptophan, kynurenine, kynurenic acid, 3-hydroxykynurenine and 3-hydroxyantranilic acid in medication-free children with ADHD combined presentation (ADHD-C), with ADHD-C and oppositional defiant disorder (ODD), and with ADHD-C and conduct disorder (CD) versus healthy controls. The study also compared several ratios that are previously suggested to reflect the activities of the KP enzymes (kynurenine/tryptophan, kynurenic acid/kynurenine, 3-hydroxykynurenine/kynurenine) or neuroprotective activity (kynurenic acid/3-hydroxykynurenine) among groups. A total of 122 patients were enrolled: 46 children with ADHD-C alone, 43 children with ADHD-C+ODD, 33 children with ADHD-C+CD and 50 healthy controls. Targeted biochemical molecules were assessed by liquid chromatography-mass spectrometry/mass spectrometry. Compared to control group, serum kynurenine levels were significantly higher in the ADHD-C group, serum 3-hydroxykynurenine levels were significantly lower in the ADHD-C and ADHD-C+ODD groups, the serum kynurenic acid/kynurenine ratio was significantly higher in the ADHD-C, ADHD-C+ODD and ADHD-C+CD groups, and the serum 3-hydroxykynurenine/kynurenine ratio was significantly lower in the ADHD-C group. These findings suggest that TMP may play a role in the pathophysiology of ADHD-C.

Alterations in serum amino acid profiles in children with attention deficit/hyperactivity disorder

The objective of the present study was to evaluate the circulating serum amino acid levels in children with attention deficit/hyperactivity disorder (ADHD). A total of 71 children with untreated ADHD and 31 neurotypical controls aged 7-14 years old were examined. Serum amino acid levels were evaluated using high-performance liquid chromatography (HPLC) with UV-detection. Laboratory quality control was performed with reference materials of human plasma amino acid levels. The obtained data demonstrated that children with ADHD were characterized by 29, 10 and 20% lower serum histidine (His), glutamine (Gln) and proline (Pro) levels compared with neurotypical children, respectively. In contrast, circulating aspartate (Asp), glutamate (Glu) and hydroxyproline (Hypro) levels exceeded the respective control values by 7, 7 and 42%. Correspondingly, the Gln-to-Glu and Pro-to-Hypro ratios were 28% and 49%, respectively, lower in ADHD cases compared with the controls. Total Gln/Glu levels were also significantly lower in ADHD patients. No significant group differences were observed between the groups in the other amino acids analyzed, including phenylalanine. Multiple linear regression analysis revealed significant associations between circulating serum Gln, lysine (Lys) (both negative) and Glu (positive) levels with total ADHD Rating Scale-IV scores. The observed alterations in Pro/Hypro and Gln/Glu levels and ratios are likely associated with the coexisting connective tissue pathology and alterations in glutamatergic neurotransmission in ADHD, respectively. Altered circulating levels of His, Lys and Asp may also be implicated in ADHD pathogenesis. However, further in vivo and in vitro studies are required in order to investigate the detailed mechanisms linking amino acid metabolism with ADHD pathogenesis.

A Different View on the Etiopathogenesis of Attention-deficit Hyperactivity Disorder from an Inflammation Perspective

Objective

Attention-deficit hyperactivity disorder (ADHD) has a complex etiology and genetic, environmental and biological factors are considered to play a role in the etiology of ADHD by mutually interacting. Recent studies have emphasized that inflammation may be present in the etiology of ADHD. This study aims to investigate the possible role of visfatin, IL-6, IL-1β and TNF-α molecules in the etiology of ADHD.

Methods

The study included 60 patients and 20 healthy controls between the ages of 6−18. Serum visfatin, IL-6, IL-1β and TNF-α levels were evaluated with enzyme-linked immunosorbent assay (ELISA) kits at a biochemistry laboratory.

Results

The study showed no statistically significant difference between children with ADHD and healthy controls in terms of visfatin, IL-6, IL-1β and TNF-α levels. When ADHD subgroups (combined and predominantly inattentive types) and the control group were compared in terms of visfatin, IL-6, IL-1β and TNF-α levels, no statistically significant difference was recorded.

Conclusion

Data on the relationship between ADHD and IL-6, IL-1β and TNF-α in this study are in compliance with the literature. However, no study was found on visfatin in ADHD. This study is the first one evaluating the ADHD-Visfatin relationship.

Increased Alopecia Areata Risk in Children with Attention-Deficit/Hyperactivity Disorder and the Impact of Methylphenidate Use: A Nationwide Population-Based Cohort Study

Alopecia areata (AA) is an autoimmune disease that causes sudden hair loss. Although few studies have reported the association between AA and attention-deficit/hyperactivity disorder (ADHD), the impact of methylphenidate (MPH) on AA has not been examined. This study examined whether AA risk is higher in children with ADHD than in those without ADHD as well as the impact of MPH use on AA risk in children with ADHD. From the Taiwan Maternal and Child Health Database, we enrolled all 1,750,456 newborns from 2004 to 2017 in Taiwan. Of them, 90,016 children received a diagnosis of ADHD whereas the remaining 1,660,440 did not. To compare AA risk in ADHD and the impact of MPH treatment on it, multiple Cox regression with adjustments for covariates (i.e., age, sex, and psychiatric comorbidities) was performed. The results indicated that 88 (0.098%) children with ADHD and 1191 (0.072%) children without ADHD had AA. Nevertheless, after adjustment for the covariates, AA risk was higher in children with ADHD than in those without ADHD (adjusted hazard ratio [aHR]: 1.30, 95% confidence interval [CI]: 1.04–1.64). Our data indicated a considerable reduction in AA risk (aHR: 0.64) among children with ADHD who received MPH than among those who did not receive MPH; however, this difference was nonsignificant, indicated by a wide 95% CI (0.32–1.25). In conclusion, ADHD and AA may share some underlying mechanisms.

Role of Oxidative Stress and Neuroinflammation in Attention-Deficit/Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder of childhood. Although abnormalities in several brain regions and disturbances of the catecholaminergic pathway have been demonstrated, the pathophysiology of ADHD is not completely understood, but as a multifactorial disorder, has been associated with an increase in oxidative stress and neuroinflammation. This review presents an overview of factors that increase oxidative stress and neuroinflammation. The imbalance between oxidants and antioxidants and also the treatment with medications are two factors that can increase oxidative damage, whereas the comorbidity between ADHD and inflammatory disorders, altered immune response, genetic and environmental associations, and polymorphisms in inflammatory-related genes can increase neuroinflammation. Evidence of an association with these factors has become valuable for research on ADHD. Such evidence opens up new intervention routes for the use of natural products as antioxidants that could have potential as a treatment against oxidative stress and neuroinflammation in ADHD.

GC-TOF-MS-Based Metabolomic Analysis and Evaluation of the Effects of HX106, a Nutraceutical, on ADHD-Like Symptoms in Prenatal Alcohol Exposed Mice

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that occurs in children characterized by inattention and hyperactivity. Prenatal alcohol exposure (PAE) can disrupt fetal neuronal development and cause an ADHD-like hyperactive behavior in the offspring. In this study, we hypothesized that metabolic disturbance would involve in ADHD neuropathology and aimed to investigate the changes in metabolite profile in PAE-induced ADHD-like model and the effects of HX106, a nutraceutical, on ADHD-like pathophysiology and metabolite changes. To this end, we administered HX106 to the mouse offspring affected by PAE (OPAE) and assessed the hyperactivity using the open field test. We observed that HX106-treated OPAE showed less hyperactive behavior than vehicle-treated OPAE. The effects of HX106 were found to be related to the regulation of dopamine transporter and D2 dopamine receptor expression. Furthermore, using gas chromatography time-of-flight mass spectrometry-based metabolomics, we explored the metabolite changes among the experimental groups. The metabolite profile, particularly related with the amino acids, linoleic acid and amino sugar pathways, was altered by PAE and reversed by HX106 treatment partially similar to that observed in the control group. Overall, this study suggest that metabolite alteration would be involved in ADHD pathology and that HX106 can be an efficient supplement to overcome ADHD by regulating dopamine signaling-related protein expression and metabolite changes.

Serum Levels of Interleukin-6 and Tumor Necrosis Factor Alpha in Children With Attention-Deficit Hyperactivity Disorder

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is a common disorder in children, but its etiology and pathogenesis are still unclear.

AIMS

The aims of this study were to measure the level of serum interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) as markers of immune system involvement in children with ADHD, and to study their correlation with symptoms severity of ADHD.

MATERIALS AND METHODS

The study was conducted on 80 children diagnosed as ADHD based on the criteria adapted from the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition. Eighty healthy children of matched age and sex served as a control group. All children enrolled in the study were subjected to history taking, clinical examination, and psychometric tests. Assay for serum IL-6 and TNF-α for all patients and controls was performed using enzyme-linked immunosorbent assay.

RESULTS

The mean serum level of IL-6 was 26.11 ± 11.14 and 6.23 ± 2.52 in children with ADHD and controls, respectively. Children with ADHD showed significantly higher serum IL-6 levels than the control group (P = 0.001). Serum IL-6 showed no significant correlation with the intelligence quotient (IQ) or the Abbreviated Conners' Rating Scale scores for parents. However, TNF-α showed no significant differences between the two groups and no significant correlation with the IQ or the Abbreviated Conners' Rating Scale scores for parents.

CONCLUSION

Serum IL-6 levels were significantly higher in children with ADHD compared to controls; however, the IL-6 levels did not correlate with ADHD symptoms severity. Increased IL-6 levels may contribute to the etiology of ADHD.

The Relationship Between Antioxidants and Inflammation in Children With Attention Deficit Hyperactivity Disorder

Introduction

Recent studies have identified Attention Deficit Hyperactivity Disorder (ADHD) as an inflammatory condition associated with immunological and oxidative responses. Therefore, it is necessary to examine these processes in these patients. The present study aimed at investigating the relationship between the dietary intake of antioxidants, Superoxide Dismutase (SOD) activity, and the serum levels of inflammatory factors in ADHD students.

Methods

This retrospective case-control study was conducted on 64 ADHD children aged 6 - 13 years. The demographic questionnaire, Food Frequency Questionnaire, and Baecke Physical Activity Questionnaire were used for data collection. SOD activity and the serum level of inflammatory factors (homocysteine, interleukin-6, and C-reactive Protein (CRP)) were measured in all patients. According to the CRP values, 32 patients were included in the case group (CRP≥1 mg/L) and 32 patients in the control group (0≤CRP<1 mg/L).

Results

There was no significant difference between the two groups in age, sex, weight, height, and body mass index. In the case group, the mean SOD activity (P=0.034), the physical activity (P=0.04), zinc intake (P=0.02), and homocysteine levels were higher than the control group (P=0.001). Of all studied variables, the best predictors were homocysteine (OR: 1.34, 95% CI: 1.082-1.670, P=0.029) and physical activity (OR: 0.85, 95% CI: 0.761-0.952, P=0.022) respectively, whereas other variables were not significant predictors.

Conclusion

The present study showed that the level of inflammatory factors in the case group was significantly higher than the control group. Homocysteine and physical activity can predict the inflammation status induced by CRP.

What Does Immunology Have to Do With Normal Brain Development and the Pathophysiology Underlying Tourette Syndrome and Related Neuropsychiatric Disorders?

Objective: The goal of this article is to review the past decade's literature and provide a critical commentary on the involvement of immunological mechanisms in normal brain development, as well as its role in the pathophysiology of Tourette syndrome, other Chronic tic disorders (CTD), and related neuropsychiatric disorders including Obsessive-compulsive disorder (OCD) and Attention deficit hyperactivity disorder (ADHD). Methods: We conducted a literature search using the Medline/PubMed and EMBASE electronic databases to locate relevant articles and abstracts published between 2009 and 2020, using a comprehensive list of search terms related to immune mechanisms and the diseases of interest, including both clinical and animal model studies. Results: The cellular and molecular processes that constitute our "immune system" are crucial to normal brain development and the formation and maintenance of neural circuits. It is also increasingly evident that innate and adaptive systemic immune pathways, as well as neuroinflammatory mechanisms, play an important role in the pathobiology of at least a subset of individuals with Tourette syndrome and related neuropsychiatric disorders In the conceptual framework of the holobiont theory, emerging evidence points also to the importance of the "microbiota-gut-brain axis" in the pathobiology of these neurodevelopmental disorders. Conclusions: Neural development is an enormously complex and dynamic process. Immunological pathways are implicated in several early neurodevelopmental processes including the formation and refinement of neural circuits. Hyper-reactivity of systemic immune pathways and neuroinflammation may contribute to the natural fluctuations of the core behavioral features of CTD, OCD, and ADHD. There is still limited knowledge of the efficacy of direct and indirect (i.e., through environmental modifications) immune-modulatory interventions in the treatment of these disorders. Future research also needs to focus on the key molecular pathways through which dysbiosis of different tissue microbiota influence neuroimmune interactions in these disorders, and how microbiota modification could modify their natural history. It is also possible that valid biomarkers will emerge that will guide a more personalized approach to the treatment of these disorders.

Possible links between gut-microbiota and attention-deficit/hyperactivity disorders in children and adolescents

An association between gut-microbiota and several neuropsychiatric conditions including autism, depression, anxiety, schizophrenia, and attention-deficit/hyperactivity disorder (ADHD) has been observed. Despite being the most prevalent neurodevelopmental disorders in children and adolescents worldwide, the etiology and curative approaches to treatment of ADHD remain unclear. There is a probability that gut-microbiota may contribute to ADHD via bidirectional communication between the gut and brain, a system known as the "gut-brain axis". Although a mechanistic link in the gut-brain axis in ADHD has been proposed, there is still a lack of information about the correlation of the microbiome profile with the mechanisms involved. The objective of this review was to summarize the diversity of the gut-microbiota and taxonomic profiles in children and adolescents with ADHD. In this review, we have provided an overview of the association between ADHD and gut-microbiota. The evidence pertinent to potentially distinctive gut-microbiota in children and adolescents with ADHD is also discussed and compared to that of their non-ADHD peers. Finally, the implications and future directions for investigation into the gut microbiome in ADHD patients are proposed.

Cortisol, inflammatory biomarkers and neurotrophins in children and adolescents with attention deficit hyperactivity disorder (ADHD) in Taiwan

BACKGROUND

Hypothalamus-Pituitary-Adrenal (HPA) axis dysregulation, inflammation and imbalance of neurotrophins have been suggested in attention deficit hyperactivity disorder (ADHD), but the results have not been conclusive. The aim of this study is to investigate the levels of salivary cortisol across 4-time points during the day, and of morning plasma inflammatory biomarkers and neurotrophins, in youth with ADHD and in typically developing youth (TD), with stratification by age, ADHD subtypes and oppositional defiant disorder (ODD) comorbidity in Taiwan.

METHODS

We conducted a case-control study measuring saliva cortisol levels at 4 different time points during the day (at awakening, noon, 1800 h and bedtime) and morning plasma levels of inflammatory and neurotrophins biomarkers in youth with ADHD (n = 98, age 6-18 years old with mean age 9.32 ± 3.05 years) and TD (n = 21, age 6-18 years old with mean age 9.19 ± 2.96 years) in Taiwan.

RESULTS

Our study showed that youth with ADHD had lower levels of bedtime salivary cortisol (effects size (ES) = -0.04, p = .023), with children with the combined form of the disorder (with inattention, hyperactivity and impulsivity all present) having the lowest awakening salivary cortisol levels. ADHD youth also had higher levels of plasma high-sensitivity C-reactive protein (hs-CRP) and interleukin (IL)-6 (ES = 0.85-1.20, p < .0001), and lower plasma tumor necrosis factor-alpha (ES = -0.69, p = .009) and brain-derived neurotrophic factors (BDNF) (ES = -1.13, p < .0001). Both ADHD groups regardless of ODD comorbidity had higher levels of IL-6 (p < .0001) and lower levels BDNF (p < .0001).

CONCLUSION

The lower bedtime salivary cortisol levels and higher levels of inflammatory biomarkers in youth with ADHD further support the role of abnormal HPA axis and inflammation in ADHD. Moreover, the lower levels of BDNF in ADHD also indicate that BDNF may be a potential biomarker in this disorder that is part of a broader biological dysfunction.