Tobacco smoking and schizophrenia: re-examining the evidence

Disentangling the effects of nicotine versus non-nicotine constituents of tobacco smoke on major depressive disorder: A multivariable Mendelian randomisation study

BACKGROUND AND AIMS

There is growing evidence that tobacco smoking causes depression, but it is unclear which constituents of tobacco smoke (e.g. nicotine, carbon monoxide) may be responsible. We used Mendelian randomisation (MR) to measure the independent effect of nicotine on depression, by adjusting the effect of circulating nicotine exposure [via nicotine metabolite ratio (NMR)] for the overall effect of smoking heaviness [via cigarettes per day (CPD)] to account for the non-nicotine constituents of tobacco smoke.

DESIGN

Univariable MR and multivariable MR (MVMR) were used to measure the total and independent effects of genetic liability to NMR and CPD on major depressive disorder (MDD). Our primary method was inverse variance weighted (IVW) regression, with other methods as sensitivity analyses.

SETTING AND PARTICIPANTS

For the exposures, we used genome-wide association study (GWAS) summary statistics among European ancestry individuals for CPD (n = 143 210) and NMR (n = 5185). For the outcome, a GWAS of MDD stratified by smoking status was conducted using individual-level data from UK Biobank (n = 35 871-194 881).

MEASUREMENTS

Genetic variants associated with NMR (n = 6) and CPD (n = 53).

FINDINGS

Univariable MR-IVW indicated a causal effect of CPD on MDD [odds ratio (OR) = 1.13, 95% confidence interval (CI) = 1.04-1.23, P = 0.003] but no clear evidence for an effect of NMR on MDD (OR = 0.98, 95% CI = 0.97-1.00, P = 0.134). MVMR indicated a causal effect of CPD on MDD when accounting for NMR (IVW: OR = 1.19, 95% CI = 1.03-1.37, P = 0.017; Egger: OR = 1.13, 95% CI = 0.89-1.43, P = 0.300) and weak evidence of a small effect of NMR on MDD when accounting for CPD (IVW: OR = 0.98, 95% CI = 0.96-1.00, P = 0.057; Egger: OR = 0.98, 95% CI = 0.96-1.00, P = 0.038).

CONCLUSIONS

The role of nicotine exposure in risk of depression cannot be entirely dismissed. However, the causal effect of tobacco smoking increasing depression risk appears to be largely independent of circulating nicotine exposure, which implies the role of alternative causal pathways.

Addressing Tobacco Use Disorder in Individuals With Mental Health Disorders: The Critical Role of Nurses

INTRODUCTION

Individuals with mental health disorders tend to smoke more frequently and intensely than the general population; however, smoking cessation efforts are still often neglected in mental health care.

METHODS

This position paper advocates for creating a more prominent role for mental health nurses in assisting individuals with severe psychiatric disorders to quit smoking.

RESULTS

Given their extensive patient contact and holistic care approach, mental health nurses are uniquely positioned to lead smoking cessation initiatives. Consequently, there is an urgent need for increased awareness, mandatory professional training and policy support to empower nurses in this critical role.

CONCLUSIONS

Strengthening the involvement of mental health nurses in smoking cessation programs could lead to reduced premature mortality and improved overall health for individuals with severe mental illnesses.

Smoking behavior is associated with suicidality in individuals with psychosis and bipolar disorder: a systematic quantitative review and meta-analysis

Smoking behavior has been well-established to be more prevalent in individuals with psychosis and bipolar disorder compared to the general population. However, reports about higher suicide attempt prevalence of smoking compared to non-smoking patients suggest that smoking behavior may contribute to identifying at-risk groups of patients in a comparatively easy manner. In the present systematic quantitative review, we provide meta-analytical evidence on the smoking and suicide attempt link in 22 studies (k = 27 independent samples; N = 11,452) of patients with psychosis and bipolar disorder. We observed a small meaningful effect of smoking on suicide attempts (OR = 1.70; 95% CI [1.48; 1.95]), indicating that smokers have 1.70 the odds of having reported a suicide attempt compared to non-smokers. This effect generalized across diagnosis type (i.e., schizophrenia vs. bipolar spectrum disorder), sample type (i.e., in-vs. outpatients), and participant sex. However, the observed summary effect appeared somewhat inflated due to publication process-related mechanisms, showing some evidence for effect-inflating publication bias and a decline effect. In all, the presently observed smoking and suicide attempt link appears to be small but meaningful and robust, thus suggesting smoking status represents a useful variable for the identification of at-risk populations for suicide attempts.

Impact of body mass index elevation, Vitamin D receptor polymorphisms and antipsychotics on the risk of Vitamin D deficiency in schizophrenia patients

Antipsychotics with weight gain as side effect and vitamin D receptor dysfunction associated with single nucleotide polymorphisms (VDR SNPs) may have different effects on vitamin D status. Hence, present study aimed to investigate the relationship between vitamin D with body mass index (BMI), antipsychotics and VDR SNPs (rs2228570, rs1544410, rs7975232 and rs731236) in Malaysian patients with schizophrenia. Serum vitamin D level was measured using competitive enzyme-linked immunosorbent assay kit. VDR SNPs were analyzed using polymerase chain reaction-restriction fragment length polymorphism. We found significantly lower serum vitamin D level in patients with schizophrenia (p < 0.01), especially those taking atypical antipsychotics (p = 0.02) and combined antipsychotics (p = 0.02) and obese (BMI ≥27.5 kg/m2) patients (p = 0.04) after adjustment for covariates. For VDR SNPs, the CT genotype of rs1544410, CA genotype of rs7975232, and AA and AG genotypes of rs731236 may contribute to the significant decreased serum vitamin D level in patients (p < 0.05). Nevertheless, these relationships may differ by populations or medical conditions. The hypotheses of volumetric dilution and sequestration of vitamin D may explain the lower vitamin D level in obese patients. In addition, lifestyle factors such as poor diet and lack of physical activity with less sunlight exposure may cause reduced vitamin D level among patients. As patients in present study were prescribed with various antipsychotics, the effect of each antipsychotic on vitamin D level could not be determined. Thus, future studies should investigate the effect of different types of antipsychotics and obesity on vitamin D level in schizophrenia.

Psychosocial Interventions for Individuals With Comorbid Psychosis and Substance Use Disorders: Systematic Review and Meta-analysis of Randomized Studies

BACKGROUND AND HYPOTHESIS

Substance use is highly prevalent among people with schizophrenia (SCZ) and related disorders, however, there is no broad-spectrum pharmacotherapy that concurrently addresses both addiction and psychotic symptoms. Psychosocial (PS) interventions, which have yielded promising results in treating psychosis and substance dependence separately, demonstrate potential but have not been systematically evaluated when combined.

STUDY DESIGN

Systematic review and random-effects meta-analyses of randomized controlled trials (RCTs) investigating PS interventions for individuals with comorbid substance use and psychotic disorders, encompassing SCZ and schizophrenia spectrum disorders (SSD). We included relevant studies published from MEDLINE, PsycINFO, and Google Scholar through May 2023.

STUDY RESULTS

We included 35 RCTs (5176 participants total; approximately 2840 with SSD). Intervention durations ranged from 30 min to 3 years. Meta-analysis did not identify a statistically significant pooled PS intervention effect on the main primary outcome, substance use (18 studies; 803 intervention, 733 control participants; standardized mean difference, -0.05 standard deviation [SD]; 95% CI, -0.16, 0.07 SD; I2 = 18%). PS intervention effects on other outcomes were also not statistically significant. Overall GRADE certainty of evidence was low.

CONCLUSIONS

At present, the literature lacks sufficient evidence supporting the use of PS interventions as opposed to alternative therapeutic approaches for significantly improving substance use, symptomatology, or functioning in people with SCZ and related disorders. However, firm conclusions were precluded by low certainty of evidence. Further RCTs are needed to determine the efficacy of PS treatments for people with dual-diagnoses (DD), either alone or in combination with pharmacotherapy.

Prevalence and correlates of cognitive impairment in schizophrenia: a cross-sectional study from a teaching hospital southern Sri Lanka

INTRODUCTIONS

This study assessed the prevalence of cognitive impairment, the degree of impairment in individual cognitive domains and sociodemographic and clinical correlates among patients attending to psychiatry clinics at Teaching Hospital, Karapitiya, Sri Lanka.

METHODS

A cross-sectional study was carried out at the psychiatry outpatient clinics of Teaching Hospital, Karapitiya, Sri Lanka. Their cognitive functions were assessed using the culturally validated Sinhala version of Addenbrooke's Cognitive Examination - III (ACE-III-S). ACE-III-S score below 85.5 was considered as significant cognitive impairment. Linear regression analysis was used to assess the factors associated with cognitive impairment. A P value of 0.05 is considered significant.

RESULTS

One hundred forty patients with schizophrenia were assessed. Of this, 125 patients had significant cognitive impairment with a prevalence of 89.3% (95% CI:84.1-94.5). Impairment in each cognitive domain was as follows: 60% in attention, 65.7% in memory, 55% in fluency, 61.4% in language, and 63.6% in visuospatial skills. Impairment was not different between cognitive domains. Advancing age (P < 0.001), shorter duration of formal education (P = < 0.001), longer duration of illness (P = < 0.001) and not having a full-time employment (P = 0.020) showed a positive association with cognitive impairment.

CONCLUSIONS

Nine out of ten patients with schizophrenia experienced significant cognitive impairment. Patients showed more than 50% impairment in all cognitive domains. The cognitive domains did not show disproportionate impairment. This study highlights the importance of introducing routine cognitive assessment protocols in patients with schizophrenia.

Genome-wide identification of the shared genetic basis of cannabis and cigarette smoking and schizophrenia implicates NCAM1 and neuronal abnormality

OBJECTIVES

Confirming the existence and composition of the shared genetic basis of Schizophrenia and cannabis and cigarette smoking has critical values for the clinical prevention and intervention of psychosis.

METHODS

To achieve this goal, we leveraged Genome-Wide summary statistics of Schizophrenia (n = 99,934), cigarette smoking (n = 518,633) and cannabis usage (n = 162,082). We applied Causal Analysis Using Summary Effect Estimates (CAUSE) and genomic structural equation modeling (GenomicSEM) to quantify the contribution of a common genetic factor of cannabis and cigarette smoking and schizophrenia (referred to as SCZ_SMO), then identified genome-wide loci that made up SCZ_SMO.

RESULTS

We estimated that SCZ_SMO explained 8.6% of Schizophrenia heritability (Z score <-2.5 in CAUSE, p<10^-20 in Genomic SEM). There were 20 independent loci showing association with SCZ_SMO at the genome-wide threshold of p<5 × 10^-8. At the top locus on chromosome 11, fine-mapping identified rs7945073 (posterior inclusion probability =0.12, p = 2.24 × 10^-32) as the top risk variants. Gene-level association and fine-mapping highlighted NCAM1, PHC2, and SEMA6D as risk genes of SCZ_SMO. Other risk genes were enriched in cortex, neuron, and dendritic spines (adjusted p<0.05). SCZ_SMO showed significant positive correlation (p<10^-6) with the genetic risk of attention deficit hyperactivity disorder (r = 0.50), lifestyle problems (r = 0.83), social deprivation (r = 0.58) and all-cause pregnant loss (r = 0.60).

CONCLUSION

Our result provided new evidence on the shared genetic basis model for the association between Schizophrenia and smoking and provided genetic and biological insights into their shared mechanism.

Folic Acid as the Adjuvant Therapy for Chronic Schizophrenia: A Comprehensive Study on Glutathione Reductase

Abstract

Prospective, observational, single-centre cohort study with an independent control group matched for age and sex aimed at investigating the significance of cholinergic activity in patients with schizophrenia: study protocol of the CLASH-study

INTRODUCTION

Alterations in the cholinergic metabolism may cause various clinical symptoms of schizophrenia. In addition to the 'monoamine hypothesis,' neuroinflammation is also discussed as a cause of schizophrenia. To date, there has been no evidence of alterations in the central cholinergic transmitter balance in patients with schizophrenia under clinical conditions. By contrast, studies in critically ill patients have established the measurement of acetylcholinesterase activity as a suitable surrogate parameter of central cholinergic transmitter balance/possible pathophysiological changes. Butyrylcholinesterase activity has been established as a parameter indicating possible (neuro)inflammatory processes. Both parameters can now be measured using a point-of-care approach. Therefore, the primary objective of this study is to investigate whether acetylcholinesterase and butyrylcholinesterase activity differs in patients with various forms of schizophrenia. Secondary objectives address the possible association between acetylcholinesterase and butyrylcholinesterase activity and (1) schizophrenic symptoms using the Positive and Negative Syndrome Scale, (2) the quantity of antipsychotics taken and (3) the duration of illness.

METHODS AND ANALYSIS

The study is designed as a prospective, observational cohort study with one independent control group. It is being carried out at the Department of Psychiatry and Psychotherapy III, Ulm University Hospital, Germany. Patient enrolment started in October 2020, and the anticipated end of the study is in January 2022. The enrolment period was set from October 2020 to December 2021 (extension required due to SARS-CoV-2 pandemic). The sample size is calculated at 50 patients in each group. Esterase activity is measured on hospital admission (acute symptomatology) and after referral to a postacute ward over a period of three consecutive days. The matched control group will be created after reaching 50 patients with schizophrenia. This will be followed by a comprehensive statistical analysis of the data set.

ETHICS AND DISSEMINATION

The study was registered prospectively in the German Clinical Trials Register (DRKS-ID: DRKS00023143,URL: https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00023143) after approval by the ethics committee of the University of Ulm, Germany Trial Code No. 280/20.

TRIAL REGISTRATION NUMBER

DRKS00023143; Pre-results.

Cigarette Smoking and Schizophrenia: Etiology, Clinical, Pharmacological, and Treatment Implications

Recent data suggests that the prevalence of smoking in schizophrenia remains high. While reports suggest that smoking increases the risk of developing schizophrenia, the potential causative role of smoking in this relationship needs further investigation. Smokers with schizophrenia are more likely to have more intense positive symptoms and lower cognitive function, but diminished intensity of extrapyramidal side effects than nonsmoking patients with schizophrenia. They were also more likely to exhibit aggressive behaviour compared to nonsmokers, which could suggest higher levels of baseline aggression. The significant cost associated with regular tobacco expenditure can detract from investment in key domains. Large-scale trials have shown that pharmacotherapy for smoking cessation is effective and does not worsen the risk of developing neuropsychiatric symptoms compared to placebo. Electronic cigarette use among schizophrenia patients is high, and there is emerging evidence supportive of its efficacy. Future improvements include large-scale trials assessing the utility, efficacy, and safety of electronic cigarettes in schizophrenia patients.