Demographic, sampling- and assay-related confounders of endogenous oxytocin concentrations: A systematic review and meta-analysis

Functional role of immunoglobulin G as an oxytocin-carrier protein

It has been long-time known that oxytocin in plasma is bound to a carrier protein, a common feature of circulating peptide hormones, however, the nature of such protein was uncertain. A recent study revealed that about 60% of oxytocin present in plasma is bound to immunoglobulin G (IgG) and that oxytocin-binding IgG plays a role of a functional oxytocin carrier protein. Here, we review the historical background and methodology leading to this discovery. Moreover, we review the data showing the functional role of oxytocin-binding IgG in the modulation of oxytocin signaling relevant to the regulation of motivated behavior and several neuropsychiatric disorders. Furthermore, the possible role of gut microbiota in the origin of such IgG is discussed and the relevant new therapeutic strategies for the enhancement of oxytocin signaling are presented.

Potential role of oxytocin in the regulation of memories and treatment of memory disorders

Oxytocin (OXT) is an "affiliative" hormone or neurohormone or neuropeptide consists of nine amino acids, synthesized in magnocellular neurons of paraventricular (PVN) and supraoptic nuclei (SON) of hypothalamus. OXT receptors are widely distributed in various region of brain and OXT has been shown to regulate various social and nonsocial behavior. Hippocampus is the main region which regulates the learning and memory. Hippocampus particularly regulates the acquisition of new memories and retention of acquired memories. OXT has been shown to regulate the synaptic plasticity, neurogenesis, and consolidation of memories. Further, findings from both preclinical and clinical studies have suggested that the OXT treatment improves performance in memory related task. Various trials have suggested the positive impact of intranasal OXT in the dementia patients. However, these studies are limited in number. In the present study authors have highlighted the role of OXT in the formation and retrieval of memories. Further, the study demonstrated the outcome of OXT treatment in various memory and related disorders.

Neuropeptides affecting social behavior in mammals: Oxytocin

Oxytocin (OXT), a neuropeptide consisting of only nine amino acids, is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Although OXT is best known for its role in lactation and parturition, recent research has shown that it also has a significant impact on social behaviors in mammals. However, a comprehensive review of this topic is still lacking. In this paper, we systematically reviewed the effects of OXT on social behavior in mammals. These effects of OXT from the perspective of five key behavioral dimensions were summarized: parental behavior, anxiety, aggression, attachment, and empathy. To date, researchers have agreed that OXT plays a positive regulatory role in a wide range of social behaviors, but there have been controversially reported results. In this review, we have provided a detailed panorama of the role of OXT in social behavior and, for the first time, delved into the underlying regulatory mechanisms, which may help better understand the multifaceted role of OXT. Levels of OXT in previous human studies were also summarized to provide insights for diagnosis of mental disorders.

A fit-for-purpose validation of a commercial radioimmunoassay for measurement of human peripheral oxytocin

Oxytocin (OT) is a peptide hormone synthesized in the hypothalamus and released into systemic circulation or other areas of the brain. Its physiological roles include action as a hormone with stimulation of uterine contractions and that as a neuromodulator with involvement in social behaviors and regulation of mood. Its small size and low levels within biological matrices make it challenging to accurately measure. The goal of this study was to demonstrate the specificity of the antibody, sensitivity, and reproducibility of the Phoenix Pharmaceuticals (PP) OT radioimmunoassay (RIA) for use in human urine, serum, and saliva. Specificity of the antibody was assessed by high pressure liquid chromatography with ultraviolet (HPLC-UV) separation and assay of the fractions. Immunoreactivity was evaluated using the percent OT bound, and the fraction retention times were compared to the retention time of an intact OT standard to determine which fractions contained OT in the extracted samples. Reproducibility was assessed by running replicates of pools of each biomatrix over several assays. Sensitivity was assessed by repeated measurement of physiologically relevant low-concentration specimens. In all tested specimens the greatest reactivity in assay corresponded to the same fraction(s) as the OT standard. Only minimal reactivity was found in the other fractions, suggesting that in an unfractionated sample the antibody reacts mostly with intact OT. Reproducibility was acceptable for all specimens and the coefficient of variation (CV) ranged from 3.72 to 8.04% and 5.89-12.8%, for intra and inter-assay, respectively. The limits of quantitation (LOQ) were sufficient for measurement of normal values in urine (0.643 & 1.43 pg/mL), serum (1.90 pg/mL), and saliva pools (0.485 & 4.42 pg/mL). In conclusion, the PP OT RIA is specific and sensitive enough for reproducible measurement of intact OT in human peripheral biological matrices.

Inaccuracies in plasma oxytocin extraction and enzyme immunoassay techniques

Numerous studies have reported extensive associations between plasma oxytocin (OXT) concentrations and various human physiological and neurobehavioral processes. Measurement of OXT is fraught with difficulty due to its low molecular weight and plasma concentrations, with no consensus as to the optimal conditions for pre-analytical sample extraction, standards for immunoassay validation or the ideal protease inhibitors to prevent OXT degradation. Previous attempts at determining the efficacy of various purification techniques such as solid phase extraction (SPE) or ultrafiltration have only utilized human plasma samples, making it difficult to dissect out whether the effect of interference comes from the extraction process itself or cross-reactivity with other proteins. By testing these on pure OXT solutions, we demonstrate poor recovery efficacy and reliability of reversed phase SPE (maximum 58.1%) and ultrafiltration (<1%) techniques, and the potential for the former to introduce interference into enzyme immunoassay (EIA) measurements. The clonality of antibodies used in EIA kits also potentially contributes to the differences in the readings obtained, and we validate an EIA kit which did not require pre-analytical sample extraction with low cross-reactivity and high reliability (intraclass correlation coefficient 0.980 (95% CI 0.896-0.999). Biochemical techniques used for measuring plasma OXT concentrations must therefore be internally validated prior to translation into clinical studies.

The Association between Oxytocin and Lower Limb Osteoarthritis: A Prospective Cohort Study

Oxytocin (OT), a neuropeptide best known for its role in emotional and social behaviors, has been linked to osteoarthritis (OA). This study aimed to investigate the serum OT level in hip and/or knee OA patients and to study its association with disease progression. Patients from the KHOALA cohort with symptomatic hip and/or knee OA (Kellgren and Lawrence (KL) scores of 2 and 3) and follow-up at 5 years were included in this analysis. The primary endpoint was structural radiological progression, which was defined as an increase of at least one KL point at 5 years. Logistic regression models were used to estimate the associations between OT levels and KL progression while controlling for gender, age, BMI, diabetes and leptin levels. Data from 174 hip OA patients and 332 knee OA patients were analyzed independently. No differences in OT levels were found between the 'progressors' and 'non-progressors' groups among the hip OA patients and knee OA patients, respectively. No statistically significant associations were found between the OT levels at baseline and KL progression at 5 years, the KL score at baseline or the clinical outcomes. Higher structural damage at baseline and severe structural progression of hip and knee osteoarthritis did not appear to be associated with a low serum OT level at baseline.

The relationship between endogenous oxytocin and vasopressin levels and the Prader-Willi syndrome behaviour phenotype

Background

Oxytocin and vasopressin systems are altered in Prader Willi syndrome (PWS). However, investigations into endogenous oxytocin and vasopressin levels as well as clinical trials evaluating the effect of exogenous oxytocin on PWS symptoms have had mixed results. It is also unknown whether endogenous oxytocin and vasopressin levels are associated with certain PWS behaviours.

Method

We compared plasma oxytocin and vasopressin and saliva oxytocin levels in 30 adolescents and adults with PWS to 30 typically developing age-matched controls. We also compared neuropeptide levels between gender and genetic subtypes within the PWS cohort and examined the relationship between neuropeptide levels and PWS behaviours.

Results

While we did not measure a group difference in plasma or saliva oxytocin levels, plasma vasopressin was significantly lower in individuals with PWS compared to controls. Within the PWS cohort, saliva oxytocin levels were higher in females compared to males and individuals with the mUPD compared to the deletion genetic subtype. We also found the neuropeptides correlated with different PWS behaviours for males and females and for genetic subtypes. For the deletion group, higher plasma and saliva oxytocin levels were related to fewer behaviour problems. For the mUPD group, higher plasma vasopressin levels were related to more behaviour problems.

Conclusion

These findings support existing evidence of a vasopressin system defect in PWS and for the first time identify potential differences in the oxytocin and vasopressin systems across PWS genetic subtypes.

Oxytocin has sex-specific effects on trust and underlying neurophysiological processes

The neuropeptide oxytocin (OT) regulates mammalian social approach behavior across sexes. Yet most OT studies in humans exclusively investigated men. Here, we studied sex differences in OT's effects on human trust behavior in 144 heterosexual participants (73 women, 71 men). Participants received 24 international units of intranasal OT or placebo treatment and played a trust game in the role of the investor while undergoing electroencephalography. Trustees were represented by photos of the other sex gradually varying in their pre-rated intensities of facial features signaling attractiveness and threat. On a behavioral level, we observed that OT increased trust in men and reduced it in women when trustees showed weak signals of attractiveness and threat. Correspondingly, on the neurophysiological level, we noted that OT intensified the P100 in male participants, but dampened it in female ones. Our findings demonstrate OT's sex- and context-specific effects on social approach behavior and an underlying early visual attention-related brain process. This evidence demonstrates the need to consider psychobiological mechanisms of sexual dimorphism in human OT research.

Advances in human oxytocin measurement: challenges and proposed solutions

Oxytocin, a neuropeptide known for its role in reproduction and socioemotional processes, may hold promise as a therapeutic agent in treating social impairments in patient populations. However, research has yet to uncover precisely how to manipulate this system for clinical benefit. Moreover, inconsistent use of standardized and validated oxytocin measurement methodologies-including the design and study of hormone secretion and biochemical assays-present unresolved challenges. Human studies measuring peripheral (i.e., in plasma, saliva, or urine) or central (i.e., in cerebrospinal fluid) oxytocin concentrations have involved very diverse methods, including the use of different assay techniques, further compounding this problem. In the present review, we describe the scientific value in measuring human endogenous oxytocin concentrations, common issues in biochemical analysis and study design that researchers face when doing so, and our recommendations for improving studies using valid and reliable methodologies.

Serum oxytocin correlated with later logical memory in older Japanese women: A 7-year follow-up study

Objectives

This study aimed to investigate the longitudinal relationship between serum oxytocin and logical memory among older adults in rural Japan and clarify sex differences in this relationship.

Measurements

The first survey was conducted from October 2009 to March 2011 (Time 1) and the second from November 2016 to September 2017 (Time 2). The final analysis for Time 1 included 385 participants (median age 75 years, interquartile range [IQR] 70-81 years) and that for Time 2 included 76 participants (median age 80 years, IQR 76-83 years). We assessed cognition, logical memory, and living conditions, and measured serum oxytocin levels. Logical memory was evaluated using the Wechsler Memory Scale-Revised Logical Memory II delayed recall part A (LM II-DR). Serum oxytocin was measured using the enzyme immunoassay method.

Results

The median (IQR) oxytocin level among men (n = 20) was 34 (16-78) pg/mL at Time 1 and 53 (28-140) pg/mL at Time 2. The median (IQR) oxytocin level among women (n = 56) was 117 (35-412) pg/mL at Time 1 and 76 (32-145) pg/mL at Time 2. The median oxytocin level among women at Time 2 was significantly lower than that at Time 1 (p = 0.004). The multivariate analysis showed that for women, LM II-DR score at Time 2 was positively associated with oxytocin level at Time 1 (p = 0.042) and negatively associated with age (p = 0.02).

Conclusions

Our study suggests that maintaining high oxytocin levels in older women may prevent age-related decline in logical memory.

Oxytocin reactivity to a lab-based stressor predicts support seeking after stress in daily life: Implications for the Tend-and-Befriend theory

Social relationships play an important role in mental and physical health, particularly during times of stress. However, little is known about the biological mechanisms underlying the tendency to seek support following stress. The Tend-and-Befriend theory suggests that oxytocin (OT) may enhance the desire for social contact in response to stress. Yet, no studies in humans have provided empirical support for the connection between stress-induced changes in endogenous OT and increased support seeking after stress. In the present study, 94 participants performed a standardized laboratory stressor and then completed two weeks of daily assessments of support seeking after stress. In line with preregistered hypotheses, stress-induced plasma OT reactivity to the laboratory stressor was associated with more frequent support seeking behaviors following stress in daily life (i.e., outside of the laboratory). Additional results suggested that attachment anxiety (but not avoidance) strengthened this association. Our findings implicate the OT system in affiliative behaviors following stress, providing empirical support for the Tend-and-Befriend theory.

Peripheral oxytocin concentrations in psychiatric disorders - A systematic review and methanalysis: Further evidence

Increased interest in understanding how changes in the oxytocinergic system are associated with the etiology and progression of psychiatric disorders has currently boosted the publication of studies. We present a systematic literature review followed by meta-analyses assessing whether peripheral oxytocin (OXT) levels among psychiatric patients differ from healthy controls, considering the moderating role of methodological aspects and samples' characteristics. The following electronic databases were searched: PubMed, Web of Science, PsycINFO, SciELO, LILACS, and Scopus. Fifty-five papers were included in the analysis, and nine independent meta-analyses were performed according to the different diagnoses. Lower OXT concentrations were found in groups of specific disorders (i.e., schizophrenia, restricting and binge-eating/purging subtypes of anorexia nervosa, and borderline personality disorder) with medium to large effect sizes. Great heterogeneity was found among the studies, so that caution is needed to interpret the results. High OXT levels with an effect size of the same magnitude were found for bipolar disorder - type I and obsessive disorder. In contrast, no differences were found for bulimia, autism spectrum, depression, or social anxiety. No meta-analyses were performed for body dysmorphic disorder, post-traumatic stress disorder, or trichotillomania because only one study was identified for each of these disorders. Altered endogenous OXT concentrations are found in several disorders addressed and must be analyzed according to each disorder's specificities.

Why Does Psychotherapy Work and for Whom? Hormonal Answers

The questions of for whom and why psychotherapy is effective have been the focus of five decades of research. Most of this knowledge is based on self-report measures. Following the biopsychosocial model of mental disorders, this article explores the potential of hormones in answering these questions. The literature on cortisol, oxytocin, and oestradiol in psychotherapy was systematically searched, focusing on (a) baseline hormonal predictors of who may benefit from psychotherapy and (b) hormonal changes as indicators of therapeutic change. The search was limited to depression and anxiety disorders. In sum, the findings show that, of all three hormones, the role of cortisol is most established and that both cortisol and oxytocin are implicated in psychotherapy, although a causal role is still waiting to be demonstrated. Moreover, there is a differential role of hormones in the psychotherapy of depression versus anxiety. The directions of research mapped in this article may elucidate how psychotherapy can be selected to match patients’ endocrine states and how hormonal levels can be manipulated to improve outcomes.

Oxytocin has 'tend-and-defend' functionality in group conflict across social vertebrates

Across vertebrate species, intergroup conflict confronts individuals with a tension between group interests best served by participation in conflict and personal interest best served by not participating. Here, we identify the neurohormone oxytocin as pivotal to the neurobiological regulation of this tension in distinctly different group-living vertebrates, including fishes, birds, rodents, non-human primates and humans. In the context of intergroup conflict, a review of emerging work on pro-sociality suggests that oxytocin and its fish and birds homologues, isotocin and mesotocin, respectively, can elicit participation in group conflict and aggression. This is because it amplifies (i) concern for the interests of genetically related or culturally similar ‘in-group’ others and (ii) willingness to defend against outside intruders and enemy conspecifics. Across a range of social vertebrates, oxytocin can induce aggressive behaviour to ‘tend-and-defend’ the in-group during intergroup contests.

This article is part of the theme issue ‘Intergroup conflict across taxa’.

Towards better hypothesis tests in oxytocin research: Evaluating the validity of auxiliary assumptions

Various factors have been attributed to the inconsistent reproducibility of human oxytocin research in the cognitive and behavioral sciences. These factors include small sample sizes, a lack of pre-registered studies, and the absence of overarching theoretical frameworks that can account for oxytocin's effects over a broad range of contexts. While there have been efforts to remedy these issues, there has been very little systematic scrutiny of the role of auxiliary assumptions, which are claims that are not central for testing a hypothesis but nonetheless critical for testing theories. For instance, the hypothesis that oxytocin increases the salience of social cues is predicated on the assumption that intranasally administered oxytocin increases oxytocin levels in the brain. Without robust auxiliary assumptions, it is unclear whether a hypothesis testing failure is due to an incorrect hypothesis or poorly supported auxiliary assumptions. Consequently, poorly supported auxiliary assumptions can be blamed for hypothesis failure, thereby safeguarding theories from falsification. In this article, I will evaluate the body of evidence for key auxiliary assumptions in human behavioral oxytocin research in terms of theory, experimental design, and statistical inference, and highlight assumptions that require stronger evidence. Strong auxiliary assumptions will leave hypotheses vulnerable for falsification, which will improve hypothesis testing and consequently advance our understanding of oxytocin's role in cognition and behavior.

Endogenous Oxytocin Levels in Autism-A Meta-Analysis

Oxytocin (OT) circuitry plays a major role in the mediation of prosocial behavior. Individuals with autism spectrum disorder (ASD) are characterized by impairments in social interaction and communication and have been suggested to display deficiencies in central OT mechanisms. The current preregistered meta-analysis evaluated potential group differences in endogenous OT levels between individuals with ASD and neurotypical (NT) controls. We included 18 studies comprising a total of 1422 participants. We found that endogenous OT levels are lower in children with ASD as compared to NT controls (n = 1123; g = -0.60; p = 0.006), but this effect seems to disappear in adolescent (n = 152; g = -0.20; p = 0.53) and adult populations (n = 147; g = 0.27; p = 0.45). Secondly, while no significant subgroup differences were found in regard to sex, the group difference in OT levels of individuals with versus without ASD seems to be only present in the studies with male participants (n = 814; g = -0.44; p = 0.08) and not female participants (n = 192; g = 0.11; p = 0.47). More research that employs more homogeneous methods is necessary to investigate potential developmental changes in endogenous OT levels, both in typical and atypical development, and to explore the possible use of OT level measurement as a diagnostic marker of ASD.

Analytical and physiological validation of an enzyme immunoassay to measure oxytocin in dog, wolf, and human urine samples

Oxytocin (OT) promotes pro-sociality, bonding, and cooperation in a variety of species. Measuring oxytocin metabolite (OTM) concentrations in urine or saliva provides intriguing opportunities to study human and animal behaviour with minimal disturbance. However, a thorough validation of analytical methods and an assessment of the physiological significance of these measures are essential. We conducted an analytical validation of a commercial Enzyme Immunoassay (EIA; Arbor OT assay kit) to measure OTM concentrations in dog, wolf, and human urine samples. To test the assay's ability to detect changes in OTM concentrations, we administered oxytocin intranasally to 14 dogs. Assay performance with regard to parallelism was acceptable. Assay accuracy and extraction efficiency for dog and wolf samples were comparable to a previously validated assay (Enzo OT assay kit) but variation was smaller for human samples. Binding sensitivity and antibody specificity were better in the Arbor assay. Average OTM concentrations were more than twice as high as in comparable samples measured with the Enzo assay, highlighting a lack of comparability of absolute values between different assays. Changes in OTM concentrations after intranasal treatment were detected reliably. The Arbor assay met requirements of a "fit-for-purpose" validation with improvement of several parameters compared to the Enzo assay.

Associations between oxytocin and vasopressin concentrations, traumatic event exposure and posttraumatic stress disorder symptoms: group comparisons, correlations, and courses during an internet-based cognitive-behavioural treatment

Background: Posttraumatic stress disorder (PTSD) is characterized by impairments in extinction learning and social behaviour, which are targeted by trauma-focused cognitive behavioural treatment (TF-CBT). The biological underpinnings of TF-CBT can be better understood by adding biomarkers to the clinical evaluation of interventions. Due to their involvement in social functioning and fear processing, oxytocin and arginine vasopressin might be informative biomarkers for TF-CBT, but to date, this has never been tested. Objective: To differentiate the impact of traumatic event exposure and PTSD symptoms on blood oxytocin and vasopressin concentrations. Further, to describe courses of PTSD symptoms, oxytocin and vasopressin during an internet-based TF-CBT and explore interactions between these parameters. Method: We compared oxytocin and vasopressin between three groups of active and former male service members of the German Armed Forces (n = 100): PTSD patients (n = 39), deployed healthy controls who experienced a deployment-related traumatic event (n = 33) and non-deployed healthy controls who never experienced a traumatic event (n = 28). PTSD patients underwent a 5-week internet-based TF-CBT. We correlated PTSD symptoms with oxytocin and vasopressin before treatment onset. Further, we analysed courses of PTSD symptoms, oxytocin and vasopressin from pre- to post-treatment and 3 months follow-up, as well as interactions between the three parameters. Results: Oxytocin and vasopressin did not differ between the groups and were unrelated to PTSD symptoms. PTSD symptoms were highly stable over time, whereas the endocrine parameters were not, and they also did not change in mean. Oxytocin and vasopressin were not associated with PTSD symptoms longitudinally. Conclusions: Mainly due to their insufficient intraindividual stability, single measurements of endogenous oxytocin and vasopressin concentrations are not informative biomarkers for TF-CBT. We discuss how the stability of these biomarkers might be increased and how they could be better related to the specific impairments targeted by TF-CBT.

Serum Oxytocin Levels and Logical Memory in Older People in Rural Japan

OBJECTIVE

The present study aimed to investigate the relationship between serum oxytocin (OT) and logical memory among older people in rural Japan.

METHODS

This was a cross-sectional study using a survey conducted from October 2009 through March 2011. Most of the study was conducted as part of a national prevalence survey of dementia in Japan. The final sample comprised 385 community-dwelling people aged 65 years or older living in rural Japan. The mean age and standard deviation were 75.7 ± 6.76 years (144 men, mean age 75.0 ± 6.48 years; 241 women, mean age 76.2 ± 6.91 years). The participants underwent screening examinations for a prevalence survey of dementia. The screening examinations were the Mini-Mental State Examination, Clinical Dementia Rating, and "logical memory A" from the Wechsler Memory Scale-Revised (WMSR). We used the WMSR Logical Memory II delayed recall score (LM II-DR) to assess logical memory. Levels of serum OT were obtained using the enzyme immunoassay method.

RESULTS

Serum OT levels were significantly higher among women than men. The present study revealed that serum OT levels were positively associated with LM II-DR in older women living in rural Japan in multiple linear regression analyses.

CONCLUSIONS

The present results suggested a positive correlation between OT and logical memory in older women living in rural Japan.

The hypothalamus in anxiety disorders

Of all mental disorders, anxiety disorders are currently the strongest contributors to the global burden of disease, with 7.3% of the general population affected worldwide. The hypothalamus is crucial hub of a network of neural structures modulating fear conditioning and extinction and, as such, highly relevant to the pathophysiology of these conditions. Three hypothalamic systems have emerged as particularly relevant in this context. First, the oxytocin system is highly likely to be involved anxiety disorders and in particular in the cognitive and behavioral deficits pertaining to social anxiety disorder. Second, peripheral markers of the hypothalamic-pituitary-adrenal axis appear altered in patients with panic disorder and generalized anxiety disorder, which may denote aberrant functioning of their central corticotropin-releasing hormone system. Furthermore, cortisol seems to augment the effects of exposure therapy in patients with specific phobia. Third, the integrity of the hypothalamic-pituitary-thyroid axis is likely compromised in panic disorder. Further, cross-disciplinary research efforts are required to shed more light on how, exactly, these hypothalamic systems interact with the neural structures involved in fear conditioning and extinction, which should ultimately open up new avenues for the prevention and treatment of anxiety disorders.

Salivary and plasmatic oxytocin are not reliable trait markers of the physiology of the oxytocin system in humans

Single measurements of salivary and plasmatic oxytocin are used as indicators of the physiology of the oxytocin system. However, questions remain about whether they are sufficiently stable to provide valid trait markers of the physiology of the oxytocin system, and whether salivary oxytocin can accurately index its plasmatic concentrations. Using radioimmunoassay, we measured baseline plasmatic and/or salivary oxytocin from two independent datasets. We also administered exogenous oxytocin intravenously and intranasally in a triple dummy, within-subject, placebo-controlled design and compared baseline levels and the effects of routes of administration. Our findings question the use of single measurements of baseline oxytocin concentrations in saliva and plasma as valid trait markers of the physiology of the oxytocin system in humans. Salivary oxytocin is a weak surrogate for plasmatic oxytocin. The increases in salivary oxytocin observed after intranasal oxytocin most likely reflect unabsorbed peptide and should not be used to predict treatment effects.

Maternal perinatal depression, circulating oxytocin levels and childhood emotional disorders at 4 years of age: The importance of psychosocial context

Oxytocin has been a hormone of interest in understanding both depression and parenting. Here, the role of oxytocin has been explored in understanding the interaction between perinatal depression, history of trauma and subsequent longer-term child socio-emotional outcomes. Data were obtained from 203 pregnant women from the Mercy Pregnancy and Emotional Wellbeing Study (MPEWS), a pregnancy cohort study with data collected across pregnancy, postpartum and until 4 years for mother and child. Maternal antenatal depression was measured using the Structured Clinical Interview for DSM-IV (SCID-IV) together with the Childhood Trauma Questionnaire to measure maternal trauma history. Maternal oxytocin levels were measured by enzyme immunoassay following extraction at four time points across pregnancy and the postpartum. The offspring consisted of 203 children followed up from birth until 4 years of age when they were assessed for DSM 5 depression and anxiety disorders (emotional disorders) using the Preschool Age Psychiatric Assessment. Maternal oxytocin levels increased over pregnancy and the postpartum in both control and depressed women with no difference between groups. Maternal childhood trauma and antenatal antidepressant use was also not associated with maternal oxytocin levels. Lower gestational age, maternal depression and early childhood trauma, and late pregnancy oxytocin concentrations were associated with later childhood emotional disorders; together they predicted 10% of variance for emotional disorders. Oxytocin is a hormone whose role in understanding intergenerational risk from pregnancy to child emotional disorders is dependent on relational context. Future research can expand on understanding these important early predictors of childhood mental health.

How Can Intranasal Oxytocin Research Be Trusted? A Systematic Review of the Interactive Effects of Intranasal Oxytocin on Psychosocial Outcomes

Over the past two decades, research about the role of oxytocin (OT) in human behavior has grown exponentially. However, a unified theory of OT effects has yet to be developed. Relatedly, growing concerns about the robustness of conclusions drawn in the field have been raised. The current article contributes to this debate by reporting on and discussing key conclusions from a systematic review of published studies addressing the interactive effects of intranasal OT (IN-OT) administration on psychosocial outcomes in a healthy population. The review indicates that (a) tested interactive IN-OT effects were highly heterogeneous; (b) for most published interactions, no replication was attempted; (c) when attempted, replications were largely unsuccessful; (d) significance was unrelated to sample size; (e) statistical power was critically low and unrelated to the rate of significant results; and (f) research practices were characteristic of an exploratory approach. This concerning state of affairs makes it virtually impossible to tease apart true from false interactive IN-OT effects. We provide constructive directions on the basis of this observation and positive predictive value simulations for future research that should help extract true effects from noise and move the IN-OT field forward.

Early posttraumatic autonomic and endocrine markers to predict posttraumatic stress symptoms after a preventive intervention with oxytocin

BACKGROUND

Efficient prevention of posttraumatic stress disorder (PTSD) needs to target individuals with an increased risk for adverse outcome after trauma. Prognostic or prescriptive biological markers assessed early posttrauma may inform personalized treatment recommendations.

OBJECTIVE

To test prognostic and prescriptive effects of early (posttraumatic) autonomic and endocrine markers on PTSD symptom development.

METHOD

Autonomic and endocrine markers were assessed within 12 days posttrauma and before treatment initiation within a randomized placebo-controlled trial investigating repeated oxytocin administration as preventive intervention for PTSD. Linear mixed effects models were used to test the effects of heart rate (variability), resting cortisol, morning cortisol and cortisol awakening response (CAR), cortisol suppression by dexamethasone and resting oxytocin on PTSD symptoms 1.5, 3 and 6 months posttrauma in men (n = 54), women using hormonal contraception (n = 27) and cycling women (n = 19).

RESULTS

We found significant prognostic effects of resting oxytocin and cortisol suppression. In women using hormonal contraception, higher oxytocin was associated with higher PTSD symptoms across follow-up. Stronger cortisol suppression by dexamethasone, reflecting increased glucocorticoid receptor feedback sensitivity, was associated with lower PTSD symptoms across follow-up in men, but with higher symptoms at 1.5 months in women using hormonal contraception. These effects were independent of treatment condition. No further significant prognostic or prescriptive effects were detected.

CONCLUSION

Our exploratory study indicates that resting oxytocin and glucocorticoid receptor feedback sensitivity early posttrauma are associated with subsequent PTSD symptom severity. Notably, prognostic effects depended on sex and hormonal contraception use, emphasizing the necessity to consider these factors in biomedical PTSD research.

Kinetics of oxytocin effects on amygdala and striatal reactivity vary between women and men

Accumulating evidence suggests that intranasal oxytocin (OXT; 24 IU) reduces amygdala responses to fear-related stimuli in men, while exerting inverse effects in women. However, OXT enhances activity of the brain reward system in both sexes. Importantly, a crucial and still open question is whether there are sex-specific dose-response relationships for the amygdala and striatal regions. To address this question, a total of 90 healthy women participated in a double-blind, placebo-controlled crossover functional magnetic resonance imaging (fMRI) study and the results were compared with our previous findings from men. Participants were randomly assigned to three doses of OXT (6 IU, 12 IU, and 24 IU) and completed an emotional face recognition task including fearful and happy faces of varying emotional intensities. Across doses, OXT enhanced amygdala reactivity to low fearful faces compared to placebo and increased responses to happy faces in the dorsal striatum in women. While treatment effects on amygdala reactivity were evident at each given dose, the OXT effect on striatal responses to social stimuli was more pronounced with higher doses, but this dose-dependent effect did not survive correction for multiple comparisons. Importantly, OXT effects on amygdala and striatal activation significantly differed between sexes and striatal baseline sexual-dimorphic response patterns were diminished after administration of OXT. Our findings suggest that OXT increases the salience of social signals by strengthening the sensitivity for these signals in the amygdala and in the striatum in women, while OXT may primarily induce anxiolysis by reducing amygdala responses in men.