Effects of tobacco smoking on neuropsychological function in schizophrenia in comparison to other psychiatric disorders and non-psychiatric controls

Verbal memory impairments in mood disorders and psychotic disorders: A systematic review of comparative studies

BACKGROUND

Mood and psychotic disorders are both associated with verbal memory impairments. Verbal memory represents an important treatment target for both disorders. However, whether the neurocognitive and neurophysiological profiles of verbal memory impairments differ between specific disorders within these two diagnostic categories and healthy controls remains unclear. The current systematic review synthesized findings from comparative studies which used behavioural and neuroimaging tasks to investigate verbal memory impairments between: (1) mood disorder, psychotic disorder, and healthy control groups; and (2) mood disorder without psychotic features, mood disorder with psychotic features, and healthy control groups.

METHODS

The search strategy combined terms related to three main concepts: 'mood disorders', 'psychotic disorders', and 'verbal memory'. Searches were executed in Embase, MEDLINE, PsycInfo, and PubMed databases. A total of 38 articles met the full eligibility criteria and were included in the final narrative synthesis. Findings were stratified by memory domain (overall composite score, verbal working memory, immediate recall, delayed recall, and recognition memory) and by illness phase (acute and non-acute).

RESULTS

Mood and psychotic disorders displayed consistent verbal memory impairments compared to healthy controls during the acute and non-acute phases. Few significant differences were identified in the literature between mood and psychotic disorders, and between mood disorders with and without psychotic features. Individuals with schizophrenia were found to have decreased immediate and delayed verbal recall performance compared to bipolar disorder groups during the acute phase. Major depressive disorder groups with psychotic features were also found to have decreased delayed verbal recall performance compared to those without psychosis during the acute phase. No consistent differences were identified between mood and psychotic disorders during the non-acute phase. Finally, preliminary evidence suggests there may be functional abnormalities in important frontal and temporal brain regions related to verbal memory difficulties in both mood and psychotic disorders.

DISCUSSION

The current findings have potential implications for the diagnosis and treatment of cognitive impairments in mood and psychotic disorders. Verbal recall memory may serve as a sensitive tool in the risk stratification of cognitive impairments for certain mood and psychotic disorders. Moreover, since no widespread differences between clinical groups were identified, the evidence supports providing targeted interventions for verbal memory, such as pharmacological and non-pharmacological interventions, through a trans-diagnostic approach in mood and psychotic disorders.

A systematic review of digital interventions for smoking cessation in patients with serious mental illness

Tobacco smoking is highly prevalent among patients with serious mental illness (SMI), with known deleterious consequences. Smoking cessation is therefore a prioritary public health challenge in SMI. In recent years, several smoking cessation digital interventions have been developed for non-clinical populations. However, their impact in patients with SMI remains uncertain. We conducted a systematic review to describe and evaluate effectiveness, acceptability, adherence, usability and safety of digital interventions for smoking cessation in patients with SMI. PubMed/MEDLINE, EMBASE, CINAHL, Web of Science, PsychINFO and the Cochrane Tobacco Addiction Group Specialized Register were searched. Studies matching inclusion criteria were included and their information systematically extracted by independent investigators. Thirteen articles were included, which reported data on nine different digital interventions. Intervention theoretical approaches ranged from mobile contingency management to mindfulness. Outcome measures varied widely between studies. The highest abstinence rates were found for mSMART MIND (7-day point-prevalent abstinence: 16-40%). Let's Talk About Quitting Smoking reported greater acceptability ratings, although this was not evaluated with standardized measures. Regarding usability, Learn to Quit showed the highest System Usability Scale scores [mean (s.d.) 85.2 (15.5)]. Adverse events were rare and not systematically reported. Overall, the quality of the studies was fair to good. Digitally delivered health interventions for smoking cessation show promise for improving outcomes for patients with SMI, but lack of availability remains a concern. Larger trials with harmonized assessment measures are needed to generate more definitive evidence and specific recommendations.

Neurobiological associations between smoking and internalizing disorders

People with severe mental disorders have a higher mortality rate due to preventable conditions like cardiovascular diseases and respiratory diseases. Nicotine addiction is a preventable risk factor, with tobacco use being twice as high in people with mental disorders. An integrative model that divides mental disorders into externalising, internalising, and thought disorders could be useful for identifying common causalities and risk factors. This review aims to examine the interface between smoking and internalising disorders, specifically schizophrenia, depressive disorders, and anxiety disorders. The review finds that there is a clear association between smoking behaviour and these disorders. Schizophrenia is associated with polymorphisms that result in an imbalance between glutamate and GABA release and abnormalities of dopaminergic pathways. Nicotine improves dopaminergic signalling and balances glutamatergic and GABAergic pathways, improving symptoms and increasing the risk of nicotine dependence. In depressive disorders, smoking is associated with functional changes in brain regions affected by smoking and self-medication. In anxiety disorders, there is a bidirectional relationship with smoking, involving the amygdala and changes in dopaminergic pathways and cortisol production. Smoking poses a threat to people living with psychiatric disorders and calls for further research to assess the interactions between nicotine dependence and internalising and thought disorders.

A systematic review of factors associated with sustained smoking abstinence in people experiencing severe mental illness following participation in a smoking intervention

OBJECTIVE

People experiencing severe mental illness report higher rates of tobacco smoking than the general population, while rates of quitting and sustaining abstinence are considerably lower. This systematic review aimed to identify factors associated with sustained abstinence in people experiencing severe mental illness following a smoking intervention.

METHOD

Searches were conducted in PubMed, PsycInfo, Scopus, Embase, Emcare, CINAHL and Cochrane Library from the inception of the e-databases until June 2022. Selection criteria included randomised and non-randomised studies of smoking cessation interventions in which most of the participants were experiencing severe mental illness, and reported a follow-up of 3 months or longer. From an initial 1498 unique retrieved records, 26 references were included detailing 17 smoking cessation intervention studies and 3 relapse prevention intervention studies. Risk of bias was assessed using the RoB2 tool for randomised study designs and the ROBINS-I tool for non-randomised designs.

RESULTS

Participation in smoking interventions was associated with higher odds of abstinence in the medium-term, but not long-term follow-ups. There was insufficient evidence that any other factors impact sustained abstinence. Most studies were considered to have some risk of bias, largely due to insufficient availability of analysis plans.

CONCLUSION

Despite an abundance of studies investigating smoking cessation in smokers experiencing severe mental illness, there is limited knowledge on the factors associated with staying quit. The inclusion of people experiencing severe mental illness in large-scale randomised control trials, in which predictors of sustained abstinence are measured in the medium and long term are needed to address this important question.

A selective literature review exploring the role of the nicotinic system in schizophrenia

Nicotine use is more prevalent in patients with psychiatric disorders, especially those diagnosed with psychotic illnesses. Previously, this higher prevalence has been partially attributed to the potential ameliorative effects of nicotine on symptom severity and cognitive impairment. Some healthcare professionals and patients perceive there is a beneficial effect of nicotine on mental health. Emerging data show that the harm associated with nicotine in the population of patients with mental health conditions outweighs any potential benefit. This paper will review the evidence surrounding the nicotinic system and schizophrenia, with a focus on any causality between nicotine and psychosis.

The impact of smoking status on cognition and brain morphology in schizophrenia spectrum disorders

BACKGROUND

Cigarette smoking is associated with worse cognition and decreased cortical volume and thickness in healthy cohorts. Chronic cigarette smoking is prevalent in schizophrenia spectrum disorders (SSD), but the effects of smoking status on the brain and cognition in SSD are not clear. This study aimed to understand whether cognitive performance and brain morphology differed between smoking and non-smoking individuals with SSD compared to healthy controls.

METHODS

Data were obtained from the Australian Schizophrenia Research Bank. Cognitive functioning was measured in 299 controls and 455 SSD patients. Cortical volume, thickness and surface area data were analysed from T1-weighted structural scans obtained in a subset of the sample (n = 82 controls, n = 201 SSD). Associations between smoking status (cigarette smoker/non-smoker), cognition and brain morphology were tested using analyses of covariance, including diagnosis as a moderator.

RESULTS

No smoking by diagnosis interactions were evident, and no significant differences were revealed between smokers and non-smokers across any of the variables measured, with the exception of a significantly thinner left posterior cingulate in smokers compared to non-smokers. Several main effects of smoking in the cognitive, volume and thickness analyses were initially significant but did not survive false discovery rate (FDR) correction.

CONCLUSIONS

Despite the general absence of significant FDR-corrected findings, trend-level effects suggest the possibility that subtle smoking-related effects exist but were not uncovered due to low statistical power. An investigation of this topic is encouraged to confirm and expand on our findings.

Substance use, microbiome and psychiatric disorders

Accumulating evidence from several studies has shown association between substance use, dysregulation of the microbiome and psychiatric disorders such as depression, anxiety, and psychosis. Many of the abused substances such as cocaine and alcohol have been shown to alter immune signaling pathways and cause inflammation in both the periphery and the central nervous system (CNS). In addition, these substances of abuse also alter the composition and function of the gut microbiome which is known to play important roles such as the synthesis of neurotransmitters and metabolites, that affect the CNS homeostasis and consequent behavioral outcomes. The emerging interactions between substance use, microbiome and CNS neurochemical alterations could contribute to the development of psychiatric disorders. This review provides an overview of the associative effects of substance use such as alcohol, cocaine, methamphetamine, nicotine and opioids on the gut microbiome and psychiatric disorders involving anxiety, depression and psychosis. Understanding the relationship between substance use, microbiome and psychiatric disorders will provide insights for potential therapeutic targets, aimed at mitigating these adverse outcomes.

The detrimental effects of smoking on the course and outcome in adults with bipolar disorder-A narrative review

BACKGROUND

Smoking is a substantial and avoidable risk for physical disability and premature death. Despite a declining tobacco use in the community of developed countries, smoking remains abundant in people with mental disorders. This narrative review highlights the epidemiology, consequences and treatment options of tobacco use disorder (TUD) and nicotine dependence (ND) in people with bipolar disorder (BD).

METHODS

The authors conducted a Medline literature search from 1970 to November 2022 using MeSH terms "bipolar disorder" x "smoking" or "nicotine" or "tobacco" that retrieved 770 results. Search results were complemented by additional literature retrieved from examining cross references and by hand search in text books. Finally, 92 references were considered as essential and selected for the educational purpose of this review.

SUMMARY OF FINDINGS

Lifetime and point prevalence of smoking in people with BD is in the range of 45-70% and thus about 2-3 times more frequent in BD than in community samples. Smoking, TUD and ND have a detrimental impact both on mental and physical health as well as mortality in people with BD. In the absence of large controlled studies in comorbid BD and TUD or ND, pharmacological treatment follows the individual guidance for each disorder. Community-based psychosocial interventions for TUD and ND appear to be suitable in people with BD, too, as well as Cognitive Behavioral (CBT) or Acceptance and Commitment (ACT) based psychotherapies.

CONCLUSIONS

Smoking is a modifiable risk factor causing increased risks both for mental and physical health in BD, and deserves more attention in treatment. More treatment research into pharmacological and psychosocial interventions in comorbid BD and TUD or ND are still needed to deliver evidence-based recommendations to physicians.

The prevalence, odds, predictors, and management of tobacco use disorder or nicotine dependence among people with severe mental illness: Systematic review and meta-analysis

The prevalence, correlates, and management of tobacco use disorder (TUD) or nicotine dependence (ND) among people with severe mental illness (SMI), namely schizophrenia, bipolar disorder (BD), and major depressive disorder (MDD), remain unclear. Therefore, a systematic review and meta-analysis was conducted. Electronic databases were systematically searched from inception to July 12, 2020, for observational studies documenting the prevalence, odds, and correlates of TUD/ND among people with SMI; randomized controlled trials (RCTs) informing the management of TUD/ND in people with SMI were also included. Random-effects meta-analyses were conducted. Sources of heterogeneity were explored. Nineteen observational studies, including 7527 participants with SMI met inclusion criteria. TUD/ND co-occurred in 33.4-65% of people with SMI. Rates were higher among males. While bupropion and varenicline represent promising treatment opportunities for schizophrenia with TUD/ND, non-pharmacological interventions require further research, mainly for people with primary mood disorders. TUD/ND represent prevalent co-occurring conditions among people with SMI. Further well-designed RCTs are warranted to inform their management.

Impact of previous tobacco use with or without cannabis on first psychotic experiences in patients with first-episode psychosis

OBJECTIVE

There is high prevalence of cigarette smoking in individuals with first-episode psychosis (FEP) prior to psychosis onset. The purpose of the study was to determine the impact of previous tobacco use with or without cannabis on first psychotic experiences in FEP and the impact of this use on age of onset of symptoms, including prodromes.

METHODS

Retrospective analyses from the naturalistic, longitudinal, multicentre, "Phenotype-Genotype and Environmental Interaction. Application of a Predictive Model in First Psychotic Episodes (PEPs)" Study. The authors analysed sociodemographic/clinical data of 284 FEP patients and 231 matched healthy controls, and evaluated first psychotic experiences of patients using the Symptom Onset in Schizophrenia Inventory.

RESULTS

FEP patients had significantly higher prevalence of tobacco, cannabis, and cocaine use than controls. The FEP group with tobacco use only prior to onset (N = 56) had more sleep disturbances (42.9% vs 18.8%, P = 0.003) and lower prevalence of negative symptoms, specifically social withdrawal (33.9% vs 58%, P = 0.007) than FEP with no substance use (N = 70), as well as lower prevalence of ideas of reference (80.4% vs 92.4%, P = 0.015), perceptual abnormalities (46.4% vs 67.4%, P = 0.006), hallucinations (55.4% vs 71.5%, P = 0.029), and disorganised thinking (41.1% vs 61.1%, P = 0.010) than FEP group with previous tobacco and cannabis use (N = 144). FEP patients with cannabis and tobacco use had lower age at first prodromal or psychotic symptom (mean = 23.73 years [SD = 5.09]) versus those with tobacco use only (mean = 26.21 [SD = 4.80]) (P = 0.011).

CONCLUSIONS

The use of tobacco alone was not related to earlier age of onset of a first psychotic experience, but the clinical profile of FEP patients is different depending on previous tobacco use with or without cannabis.

Age at illness onset and physical activity are associated with cognitive impairment in patients with current diagnosis of major depressive disorder

BACKGROUND

Cognitive impairment has been reported in patients with Major Depressive Disorder (MDD). This study aims to explore the association between lifestyle habits and health-related factors and the presence of cognitive symptoms in MDD patients.

METHODS

Demographic, clinical, health-related variables and cognitive scores measured with the Cambridge Neuropsychological Test Automated Battery (CANTAB) were compared between 74 patients with current MDD and 68 healthy controls (HC). To test the hypothesis of associated factors to cognitive symptoms, multivariate backward stepwise linear regression models were run.

RESULTS

Significant neuropsychological deficits were evident in MDD compared with HC in the global cognitive index (F=8.29; df=1, 140; p=0.005). In the regression analysis performed on MDD and HC, years of schooling (β=-0.11; p=<0.001), job status (β=-0.50; p=0.016), physical activity (β=-0.25; p=0.04) and age at illness onset (β=0.17; p=0.017) were statistically significant factors associated to cognitive impairment. The regression model ran in HC showed that only years of schooling were significant (β=-0.07; p=<0.001) in this group.

LIMITATIONS

Sample size was relatively small. Everyday cognitive skills were not evaluated.

CONCLUSIONS

MDD patients have cognitive deficits. These deficits are linked with the years of education, job status, age of onset of the disease and the performance of physical activity. These results support the importance of the implementation of interventions targeting the cognitive reserve and lifestyle habits of MDD patients, in addition to the conventional therapeutic approach focused on symptoms control.

Efficacy of nicotine administration on obsessions and compulsions in OCD: a systematic review

BACKGROUND

Preliminary studies have tested nicotine as a novel treatment for OCD patients who respond partially/incompletely or not at all to first and second-line treatment strategies, with the former represented by SSRIs or clomipramine, and the latter by switching to another SSRI, or augmentation with atypical antipsychotics, and/or combination with/switching to cognitive-behavioural therapy. Some studies found nicotine-induced reduction of obsessive thoughts and/or compulsive behaviour in OCD patients. We aimed to evaluate the efficacy of nicotine administration in OCD patients.

METHODS

We searched the PubMed, ScienceDirect Scopus, CINHAL, Cochrane, PsycINFO/PsycARTICLES, and EMBASE databases from inception to the present for relevant papers. The 'Preferred Reporting Items for Systematic Review and Meta-Analyses' (PRISMA) standards were used. We included all studies focusing on the effects of nicotine administration on OCD patients' obsessions or compulsions. Studies could be open-label, cross-sectional, randomized controlled trials, case series or case reports.

RESULTS

A total of five studies could be included. Nicotine administration may ameliorate behavioural features and recurrent thoughts of severe, treatment-resistant OCD patients; however, in one study it was not associated with OC symptom improvement or cognitive enhancement across various executive function subdomains.

CONCLUSIONS

Although encouraging, the initial positive response from the use of nicotine in OCD needs testing in large controlled studies. This, however, raises ethical issues related to nicotine administration, due to its addiction potential, which were not addressed in the limited literature we examined. As an alternative, novel treatments with drugs able to mimic only the positive effects of nicotine could be implemented.

Chronic smoking and cognition in patients with schizophrenia: A meta-analysis

BACKGROUND

Patients with schizophrenia display a very high rate of smoking in comparison with the general population. The aim of the present meta-analysis was to assess the association between cognitive performances and smoking status in patients with schizophrenia.

METHODS

This review was registered at PROSPERO, number CRD42019126758. After a systematic search on MEDLINE, PsycINFO, and clinicaltrials.gov databases, all studies measuring neurocognitive performances in both smoking and nonsmoking patients with a diagnosis of schizophrenia were included. Original data were extracted. Standardized mean differences (SMD) were calculated with the means and standard deviations extracted using a random-effect model. Cognitive performances were compared between smoking and nonsmoking patients with schizophrenia. Meta-regressions were performed to explore the influence of sociodemographic and clinical variables on SMD.

RESULTS

Eighteen studies were included in this meta-analysis. Chronic smoking in patients with schizophrenia, compared to nonsmoking, was associated with a significant more important impairment in attention (p = 0.02), working memory (p < 0.001), learning (p < 0.001), executive function (EF) reasoning/problem solving (p < 0.001) and speed of processing (p < 0.001), but not in delayed memory, EF abstraction/shifting, EF inhibition and language. The meta-regression analysis found that attention impairment could be influenced by age (p < 0.001) and Positive and Negative Syndrome Scale (PANSS) total score (p = 0.006).

CONCLUSIONS

This meta-analysis provides strong evidence that, in patients with schizophrenia, chronic smoking is related to cognitive impairment. This association emphasizes the importance of paying careful attention to both tobacco addiction and cognitive functioning in patients with schizophrenia.

Passive Smoking and Disease Severity in Childhood Pneumonia Under 5 Years of Age

OBJECTIVE

To objectively investigate the effect of passive smoking on pneumonia and disease severity in children aged less than 5 years by using cotinine as an indicator of passive smoking.

METHODS

Between December 2015 and April 2016, children aged less than 5 years with pneumonia and age-matched healthy controls were included in this study, which was conducted at three tertiary pediatric pulmonology centers. A questionnaire was given to the parents regarding demographic data and smoking status at home. Urinary cotinine/creatinine ratio (CCR) was measured. The data from the pneumonia and control groups, as well as children with mild and severe pneumonia within the pneumonia group, were compared.

RESULTS

A total of 227 subjects were included in the study; there were 74 children in the pneumonia group and 153 in the control group. The mean age of all the children was 33.4 ± 1.28 months. Of all subjects, 140 were male and 102 were exposed to passive smoking by their parents at home. There were statistically significant differences in age, number of people in the home, and mother's and father's age between the control and pneumonia groups (p < 0.05). No difference was found in the CCR in the control and pneumonia group (p > 0.05). Age and urinary CCR were significantly different between children with mild and severe pneumonia (p < 0.05).

CONCLUSION

We showed that passive smoking exposure was associated with the development of severe pneumonia in children. Further studies are needed to examine the underlying cause in detail.

Call to action regarding the vascular-bipolar link: A report from the Vascular Task Force of the International Society for Bipolar Disorders

OBJECTIVES

The association of bipolar disorder with early and excessive cardiovascular disease was identified over a century ago. Nonetheless, the vascular-bipolar link remains underrecognized, particularly with regard to how this link can contribute to our understanding of pathogenesis and treatment.

METHODS

An international group of experts completed a selective review of the literature, distilling core themes, identifying limitations and gaps in the literature, and highlighting future directions to bridge these gaps.

RESULTS

The association between bipolar disorder and vascular disease is large in magnitude, consistent across studies, and independent of confounding variables where assessed. The vascular-bipolar link is multifactorial and is difficult to study given the latency between the onset of bipolar disorder, often in adolescence or early adulthood, and subsequent vascular disease, which usually occurs decades later. As a result, studies have often focused on risk factors for vascular disease or intermediate phenotypes, such as structural and functional vascular imaging measures. There is interest in identifying the most relevant mediators of this relationship, including lifestyle (eg, smoking, diet, exercise), medications, and systemic biological mediators (eg, inflammation). Nonetheless, there is a paucity of treatment studies that deliberately engage these mediators, and thus far no treatment studies have focused on engaging vascular imaging targets.

CONCLUSIONS

Further research focused on the vascular-bipolar link holds promise for gleaning insights regarding the underlying causes of bipolar disorder, identifying novel treatment approaches, and mitigating disparities in cardiovascular outcomes for people with bipolar disorder.

Effects of Tobacco Smoking Status on Verbal Learning and Memory in Patients With Schizophrenia and Non-Psychiatric Controls

BACKGROUND AND OBJECTIVES

Patients with schizophrenia have higher rates of tobacco smoking compared to the general population. Moreover, these patients have deficits in cognition, including verbal learning and memory. However, it is not clear whether smoking status alters verbal learning and memory in schizophrenia. We examined the effects of smoking abstinence and reinstatement on verbal learning and memory in people with schizophrenia and nonpsychiatric controls and other cognitive domains as exploratory.

METHODS

Smoking participants (N = 28; 14 schizophrenia smokers; 14 nonpsychiatric smokers) were studied under smoking satiated, overnight abstinence and smoking reinstatement conditions. Nonsmokers ( n = 30; 15 schizophrenia nonsmokers; 15 nonpsychiatric nonsmokers) were also studied. A comprehensive cognitive battery was administered including verbal learning and memory using the Hopkins Verbal Learning Test-Revised (HVLT-R).

RESULTS

A 2 (diagnosis) × 2 (smoking status) repeated measures analysis of variance with time (session) as the within-subjects factor and diagnosis and smoking status as the between-subject factors was performed for HVLT-R and other cognitive outcomes. Smoking abstinence produced a decline in verbal memory of the HVLT discrimination index in smokers with schizophrenia that was partially revised by reinstatement, although trends for other HVLT measures were not statistically significant.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Acute cigarette smoking and abstinence may selectively alter verbal learning and memory deficits in smokers with schizophrenia compared to nonpsychiatric smoking controls and nonsmokers, but additional studies are needed to confirm the preliminary findings in this small sample. (Am J Addict 2019;00:1-9).

Reasons for smoking and barriers to cessation among adults with serious mental illness: A qualitative study

AIMS

Most research into reasons for smoking among adults with serious mental illness (SMI) has focused on reasons related to SMI symptoms. The current study reports reasons for smoking and barriers to cessation that are both related and unrelated to SMI symptoms among adults with SMI.

METHODS

Four focus groups were conducted among current smokers receiving outpatient care for a psychotic disorder in 2017 (N = 24). Participants were asked why they currently smoke and their barriers to quitting smoking.

RESULTS

Smoking as a coping mechanism and to self-medicate SMI symptoms were reasons for current smoking and barriers to cessation. Avoidance of other unhealthy behaviors, routine, and enjoyment emerged as reasons for smoking and barriers to cessation that were unrelated to mental illness.

CONCLUSION

Consideration of factors that are both related and unrelated to SMI symptoms in smoking cessation interventions and brief cessation counseling may improve cessation success in this population.

The relationship between nicotine and psychosis

Cigarette smoking is strongly associated with psychotic disorders such as schizophrenia. For several decades it was assumed that the relationship could be explained by reverse causation; that smoking was secondary to the illness itself, either through self-medication or a process of institutionalization, or was entirely explained by confounding by cannabis use or social factors. However, studies have exposed that such hypotheses cannot fully explain the association, and more recently a bidirectional relationship has been proposed wherein cigarette smoking may be causally related to risk of psychosis, possibly via a shared genetic liability to smoking and psychosis. We review the evidence for these candidate explanations, using findings from the latest epidemiological, neuroimaging, genetic and preclinical work.

Cognitive functions in smoking and non-smoking patients with schizophrenia: A systematic review and meta-analysis of comparative studies

The "Self-medication hypothesis" that has been developed to explain the effect of nicotine in improving aspects of cognitive impairment in schizophrenia remains controversial. This systematic review and meta-analysis compared cognitive functions between smoking and non-smoking schizophrenia patients. The PubMed, PsycINFO, EMBASE, Web of Science, and Cochrane Library databases were systematically and independently searched. Basic demographic and clinical characteristics, smoking history and cognitive performance were recorded. Seven of the 11 studies included in the study, had meta-analyzable data. Compared to non-smoking schizophrenia patients, their smoking counterparts showed significant deficits on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)-immediate memory (n = 739), the RBANS-total score (n = 739) and the Continuous Performance Test-Identical Pairs (n = 157). Two of the 4 studies without meta-analysable data did not report significant group difference in performance on the Wechsler Digit Span Task and the Beck Cognitive Insight Scale, while the other 2 studies found that non-smokers outperformed than smokers in problem solving and visual learning. In conclusion, this systematic review and meta-analysis found that smoking schizophrenia patients had worse performance in certain cognitive tasks than non-smoking patients, casting doubts on the validity of the "self-medication hypothesis" that needs to be further examined.

Neurobiological Determinants of Tobacco Smoking in Schizophrenia

Purpose of review: To provide an overview of the underlying neurobiology of tobacco smoking in schizophrenia, and implications for treatment of this comorbidity. Recent findings: Explanations for heavy tobacco smoking in schizophrenia include pro-cognitive effects of nicotine, and remediation of the underlying pathophysiology of schizophrenia. Nicotine may ameliorate neurochemical deficits through nicotine acetylcholine receptors (nAChRs) located on the dopamine, glutamate, and GABA neurons. Neurophysiological indices including electroencephalography, electromyography, and smooth pursuit eye movement (SPEM) paradigms may be biomarkers for underlying neuronal imbalances that contribute to the specific risk of tobacco smoking initiation, maintenance, and difficulty quitting within schizophrenia. Moreover, several social factors including socioeconomic factors and permissive smoking culture in mental health facilities, may contribute to the smoking behaviors (initiation, maintenance, and inability to quit smoking) within this disorder. Summary: Tobacco smoking may alleviate specific symptoms associated with schizophrenia. Understanding the neurobiological underpinnings and psychosocial determinants of this comorbidity may better explain these potential beneficial effects, while also providing important insights into effective treatments for smoking cessation.

Gender differences and risk factors for smoking among patients with various psychiatric disorders in Saudi Arabia: a cross-sectional study

Background

The higher prevalence of smoking among psychiatric patients is well established. However, gender-specific associations have rarely been the focus of studies among patients with various psychiatric disorders. The aim of this study was to estimate the gender-specific prevalence of current smoking by psychiatric patients and its association with various psychiatric disorders and the use of psychotropic medications.

Methods

A cross-sectional observational study was performed between July 2012 and June 2014. Patients were recruited from six hospitals located in the five regions of Saudi Arabia.

Results

Of the 1193 patients, 402 (33.7%) were current smokers. The incidence of current smoking was much higher among males than females (58.3% versus 6.7%, p < 0.001). In one or both genders, current smoking was associated with marital status, education, family income, residence, obesity, physical activity, substance abuse, inpatient status, previous psychiatric hospitalization, and age at onset of psychiatric illness. In both gender, smoking was higher in patients who had a secondary psychiatric disorder (66.7% versus 37.5%, respectively), those who had a primary psychotic disorder (63.7% versus 12.3%), and those taking antipsychotic medication (64.1% versus 8.3%) but lower in patients who had a primary depressive disorder (40.3% versus 4.3%), those who had a primary anxiety disorder (45.8% versus 0.0%), and those taking antidepressant medications (53.7% versus 3.6%). In a multivariate analysis adjusted for demographic/clinical characteristics and psychiatric disorders, current smoking was independently associated with primary psychotic disorders in females (OR = 3.47, 1.45–8.27, p = 0.005) but not in males. In a multivariate analysis adjusted for demographic/clinical characteristics and psychotropic medications, current smoking was independently associated with antipsychotic medication use in males (OR = 1.79, 1.10–2.93, p = 0.020). Current smoking was strongly associated with substance abuse in both univariate and multivariate analyses.

Conclusion

The prevalence of current smoking is high with marked gender difference in a large sample of mixed psychiatric patients in Saudi Arabia. Smoking-cessation programs may be urgently needed for these vulnerable patients.

Tobacco smoking and its association with cognition in first episode psychosis patients

Available evidence suggests that nicotine may enhance cognitive functioning. Moreover, it has been suggested that the high prevalence of smoking in people with schizophrenia is in part due to self-medication behaviour to alleviate cognitive deficits. We assessed the association between tobacco smoking and cognitive functioning in a large population of first episode psychosis (FEP) patients (n=304) and healthy controls (n=156). Smokers were not tobacco deprived, or were minimally deprived (≤2h). Verbal memory, visual memory, working memory, processing speed, executive function, motor dexterity and attention were assessed. The smoking prevalence among the FEP group was 57% (n=174). The age at which patients began smoking cigarettes regularly was 16.2years (SD=3.1), an average of 12years before experiencing the first frank symptoms of psychosis (age of onset=28.8; SD=9.3). The number of cigarettes smoked per day was 19.6 (SD=9.4), significantly more than healthy controls [11.0 (SD=7.6); p<0.001]. ANCOVA analysis did not show any significant difference between smokers and non-smokers in in the performance of any of the cognitive tasks in the FEP group or in the healthy control group, independent of gender, age, education or premorbid IQ. This suggests chronic exposure to nicotine through cigarette smoking is not associated with cognitive functioning in first-episode psychosis. These findings do not support the nicotine self-medication hypothesis as a contributor to the high prevalence of smoking among individuals suffering from serious mental illness.

Assessment of the Association Between Cigarette Smoking and Cognitive Performance in Patients With Schizophrenia-Spectrum Disorders: A Case-Control Study

The prevalence of cigarette smoking is significantly higher in patients with schizophrenia compared to the general population. Schizophrenia is also characterized by cognitive impairments that can be detected in the premorbid phase of illness. However, studies addressing the association between cigarette smoking and cognition in patients with psychosis have provided mixed findings. Therefore, the aim of this study was to assess the relationship between tobacco smoking and cognitive performance in patients with schizophrenia. In this case-control study, we recruited 67 inpatients with schizophrenia (34 cigarette smokers) and 62 healthy controls (30 cigarette smokers) at two clinical sites (Wroclaw and Szczecin, Poland). Cognitive performance was examined using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Smoking dependence was determined using the Fagerström Test for Nicotine Dependence (FTND) and the pack-year index. Results show that, after adjustment for potential confounders, smokers with schizophrenia presented significantly lower scores on delayed memory tests compared to non-smokers with schizophrenia (F = 11.07, p = 0.002). In healthy controls, after adjustment for age, sex, and education level, smokers had significantly lower scores in immediate memory (47.1 ± 6.4 vs. 52.0 ± 4.0, F = 11.64, p = 0.001), visuospatial/constructional functions (34.8 ± 3.8 vs. 37.7 ± 1.8, F = 12.86, p = 0.001) and global cognition (177.0 ± 15.7 vs. 191.2 ± 14.0, F = 12.63, p = 0.001) compared to non-smokers. There were no significant correlations between FTND scores or pack-year index and cognitive performance neither in patient nor control group. Our results show that cigarette smoking is related to worse delayed memory performance in schizophrenia patients as well as deficits of immediate memory, visuospatial/constructional functions, and global cognition in controls. Longitudinal studies are required to establish causal interference between smoking and cognition in patients with schizophrenia.

Smoking status and its relationship to demographic and clinical characteristics in first episode psychosis

Elevated rates of cigarette smoking are observed prior to the onset of psychosis and remain stable early in the illness. Cannabis use frequently co-occurs with cigarette smoking and is independently associated with distinct clinical outcomes. However, past research has not controlled for cannabis use in cigarette smokers with first episode psychosis (FEP), limiting conclusions on the unique relationship of cigarette smoking to the demographic and clinical profiles of these patients. The present study therefore aimed to: (1) Determine the prevalence and patterns of cigarette smoking and its co-use with cannabis in FEP, and (2) Examine the demographic, clinical, cognitive, and functional characteristics associated with cigarette smoking status, after adjusting for frequency of cannabis use. Patients entering specialized treatment for FEP (N = 140) were divided into groups according to their current smoking status: 66 non-smokers (0 cigarettes/day), 47 light/moderate smokers (1-19 cigarettes/day; M = 9.81, SD = 3.93), and 27 heavy smokers (≥20 cigarettes/day; M = 26.39, SD = 6.31). The prevalence of cigarette smoking was 53% and smoking status was highly associated with frequency of cannabis use. After adjusting for cannabis use, significant between-group differences emerged. Heavy smokers were older at program entry and had a later age of onset of psychosis than light/moderate and non-smokers. Non-smokers had more education, better neurocognitive performance, and higher levels of functioning than light/moderate and heavy smokers. Prospective, longitudinal studies are needed to better understand the clinical significance of tobacco use and factors that contribute to the initiation and continuation of smoking behaviours in FEP.

Schizophrenia, smoking status, and performance on the matrics Cognitive Consensus Battery

Cognitive deficits and high rates of nicotine dependence are consistently documented in the schizophrenia literature. However, there is currently no consensus about how regular smoking influences cognition in schizophrenia or which cognitive domains are most affected by chronic smoking. Previous studies have also failed to disambiguate the effects of chronic nicotine from those of acute exposure. The current study uses a novel approach to testing nicotine addicted patients at a time-point between acute enhancement and withdrawal and implements the MATRICS Cognitive Consensus Battery (MCCB) to compare the overall cognitive performance of regular smokers (n=40) and nonsmokers (n=36) with schizophrenia. Controlling for age, gender, and education, smokers with schizophrenia were significantly more impaired on a visual learning task, the Brief Visuospatial Memory Test-Revised (BVMT-R), than their nonsmoking peers. Among smokers, smoking behavior (i.e., exhaled carbon monoxide levels of smokers) predicted BVMT-R T score; greater smoking was associated with more impaired visual learning. Negative symptom severity was not predictive of greater visual learning deficits in smokers or nonsmokers. Future longitudinal research will be required to determine if there is a dose-response relationship between chronic nicotine and visual learning impairment in patients at various stages of psychotic illness.

Not All Differences between Patients with Schizophrenia and Healthy Subjects Are Pathological: Performance on the Conners' Continuous Performance Test

OBJECTIVE

This study analyzed attentional performance in patients with schizophrenia during a continuous performance task requiring a high response rate.

METHOD

The Conners' Continuous Performance Test-II (CPT-II) was administered to 64 patients with schizophrenia and 64 healthy comparison subjects. A cross-sectional design was used in order to allow analysis of the means between patients and healthy subjects. Differences in performance were assessed for significance using ANCOVA. Percentiles were also analyzed in order to determine whether a participant showed normal or pathological performance. Pearson's correlation was used to detect possible relationships between attentional performance and psychopathology.

RESULTS

Of the 12 CPT-II measures, response style and slowing of reaction time (RT) between targets increased to similar extents between patients and healthy comparison subjects. Patients performed significantly less well than non-patient group on all other measures. Nevertheless, patient's performance on four of these measures remained within the normal range, and patient's performance on the remaining measures qualified as pathological only in the case of variability in hit RT. No significant correlations between attention performance and symptoms were found.

CONCLUSIONS

These results suggest that although patients may show lower attentional functioning than non-patients on tasks requiring a high response rate, their attentional performance remains within the normal range on most dimensions.

Effects of varenicline on motor cortical plasticity in non-smokers with schizophrenia

BACKGROUND

Nicotinic acetylcholine receptors (nAChR) have been implicated in the pathophysiology of schizophrenia, and deficits in this system may contribute to high rates of cigarette smoking in this population. nAChR stimulation may modulate neuroplasticity, or long-term potentiation (LTP), which is a key mediator of cognitive performance. Varenicline is a nAChR partial agonist that may improve cognitive deficits in both smokers and non-smokers with schizophrenia; however, the mechanism by which varenicline alters cognition in schizophrenia remains unclear. Thus, the aim of this randomized, double-blind, placebo-controlled, crossover study was to determine the effects of varenicline on LTP-like plasticity indexed through transcranial magnetic stimulation (TMS) in non-smokers with schizophrenia.

METHODS

Varenicline (0.5mg BID × 5 doses) or placebo was administered to 9 non-smokers with schizophrenia and 10 non-smoker healthy subjects. LTP-like plasticity was induced by TMS and paired associative stimulation (PAS) at 0.1Hz to the left motor cortex and measured every 15min for two hours post-PAS.

RESULTS

There was a significant diagnosis × medication interaction on peak potentiation (F (3, 34)=6.04, p<0.02) and post-hoc analyses indicated that varenicline significantly increased LTP in schizophrenia and decreased LTP in healthy subjects.

CONCLUSIONS

These preliminary findings suggest that varenicline may produce differential effects in non-smoking schizophrenia compared to control subjects. Given the role of LTP in learning and memory, these observations may suggest the potential for varenicline in the treatment of cognitive deficits in patients with schizophrenia.

The association among smoking, HSV-1 exposure, and cognitive functioning in schizophrenia, bipolar disorder, and non-psychiatric controls

Previous investigations have found that smokers with schizophrenia demonstrate reduced performance on cognitive tasks compared to non-smokers. However previous studies have not taken into account other environmental factors associated with cognitive functioning such as exposure to Herpes Simplex Virus type 1 (HSV-1). We examined these factors in a sample consisting of individuals with schizophrenia (n=773), bipolar disorder (n=493), or controls without a psychiatric disorders (n=548). Participants were assessed on a cognitive battery, the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and had a blood sample drawn to measure seropositivity to HSV-1. Within each group linear regression models were constructed to determine whether cigarette smoking and HSV-1 seropositivity were jointly associated with cognitive functioning after adjusting for relevant covariates. Within the schizophrenia group, the effect size of lower total cognitive score was -0.279 (p<0.0001) for individuals who were both smokers and HSV-1 seropositive and a significant effect was found in all cognitive domains. The odds of being in the highest quartile of RBANS Total score were significantly lower for smokers (OR=0.58, 95% CI 0.41, 0.82, p=0.002). Smoking was not as consistently associated with levels of cognitive functioning in the bipolar disorder or the non-psychiatric control group. While experimental studies show that nicotine transiently improves functioning on sensory gating and attention tasks known to be deficient in schizophrenia, long-term nicotine exposure via smoking appears to have an adverse effect on cognitive functioning.

The effects of cigarette smoking behavior and psychosis history on general and social cognition in bipolar disorder

OBJECTIVES

Several studies have documented the prevalence and effects of cigarette smoking on cognition in psychotic disorders; fewer have focused on bipolar disorder (BD). Cognitive and social dysfunction are common in BD, and the severity of these deficits may be related both to illness features (e.g., current symptoms, psychosis history) and health-related behaviors (e.g., smoking, alcohol use). The current study assessed the influence of cigarette smoking on general and social cognition in a BD cohort, accounting for illness features with a focus on psychosis history.

METHODS

We assessed smoking status in 105 euthymic patients with BD, who completed a comprehensive battery including social (facial affect recognition, emotional problem-solving, and theory of mind) and general (the MATRICS Consensus Cognitive Battery and executive functioning) cognitive measures. We compared smokers vs nonsmokers on cognitive performance and tested for the effects of psychosis history, premorbid intellectual functioning, substance use, and current affective symptoms.

RESULTS

Within the nonpsychotic subgroup with BD (n=45), smokers generally outperformed nonsmokers; by contrast, for subjects with BD with a history of psychosis (n=41), nonsmokers outperformed smokers. This pattern was noted more globally using a general composite cognitive score and on social/affective measures assessing patients' ability to identify emotions of facial stimuli and solve emotional problems.

CONCLUSIONS

Cigarette smoking differentially affects performance on both general and social cognition in patients with BD as a function of psychosis history. These results suggest that there may be at least partially divergent underlying neurobiological causes for cognitive dysfunction in patients with BD with and without psychosis.

Effects of caffeine intake and smoking on neurocognition in schizophrenia

Although most studies support the beneficial effects of caffeine on neurocognition, its effects have never been assessed in psychiatric patients. In addition, results from studies in smokers are contradictory. Moreover, there are no data available about the neurocognitive effects of caffeine and tobacco together. We explored the concomitant effects of regular caffeine and tobacco intake on neurocognition in 52 schizophrenic patients and 61 healthy controls. Verbal fluency, processing speed, and working, visual and verbal memory were assessed. For each measurement, two tasks with two levels of complexity were administered. Our results showed that caffeine intake had beneficial effects on male schizophrenic patients only in complex tasks requiring deeper cognitive processing (semantic fluency, cognitive speed, working memory, and visual memory). Female patients and controls were unaffected. In contrast, smoking had a negative effect on male, but not on female, schizophrenic patients in semantic fluency. The effects of smoking in controls were inconsistent. In conclusion, our data showed, for the first time, beneficial effects of caffeine intake on neurocognition in male schizophrenic patients. These data suggest that further research of therapeutics based on caffeine is needed, as this could be beneficial for schizophrenic patients. In contrast, smoking appears to be detrimental.

Evaluating the relationship between cannabis use and IQ in youth and young adults at clinical high risk of psychosis

Among people with psychosis, those with a history of cannabis use show better cognitive performance than those who are cannabis naïve. It is unknown whether this pattern is present in youth at clinical high risk (CHR) of psychosis. We evaluated relationships between IQ and cannabis use while controlling for use of other substances known to impact cognition in 678 CHR and 263 healthy control (HC) participants. IQ was estimated using the Vocabulary and Block Design subtests of the Wechsler Abbreviated Scale of Intelligence. Drug and alcohol use severity and frequency were assessed with the Alcohol and Drug Use Scale, and we inquired participants' age at first use. CHR were further separated into early and late age at onset of cannabis use sub-groups, and low-, moderate- and high-frequency sub-groups. No significant differences in IQ emerged between CHR or HC cannabis users vs. non-users, or between use frequency groups. CHR late-onset users showed significantly higher IQ than CHR early-onset users. Age at onset of cannabis use was significantly and positively correlated with IQ in CHR only. Results suggest that age at onset of cannabis may be a more important factor for IQ than use current use or use frequency in CHR.

Smoking cessation and reduction in people with chronic mental illness

The high prevalence of cigarette smoking and tobacco related morbidity and mortality in people with chronic mental illness is well documented. This review summarizes results from studies of smoking cessation treatments in people with schizophrenia, depression, anxiety disorders, and post-traumatic stress disorder. It also summarizes experimental studies aimed at identifying biopsychosocial mechanisms that underlie the high smoking rates seen in people with these disorders. Research indicates that smokers with chronic mental illness can quit with standard cessation approaches with minimal effects on psychiatric symptoms. Although some studies have noted high relapse rates, longer maintenance on pharmacotherapy reduces rates of relapse without untoward effects on psychiatric symptoms. Similar biopsychosocial mechanisms are thought to be involved in the initiation and persistence of smoking in patients with different disorders. An appreciation of these common factors may aid the development of novel tobacco treatments for people with chronic mental illness. Novel nicotine and tobacco products such as electronic cigarettes and very low nicotine content cigarettes may also be used to improve smoking cessation rates in people with chronic mental illness.

Current smoking is associated with worse cognitive and adaptive functioning in serious mental illness

OBJECTIVE

Cigarette smoking is highly prevalent among people with bipolar disorder or schizophrenia. Few studies have examined whether smoking history is associated with adaptive functioning among individuals diagnosed with these serious mental illnesses.

METHOD

In a large relatively homogenous cohort of patients with either bipolar disorder (n=363) or schizophrenia (n=400), we investigated the association between cigarette smoking status, intensity, and cumulative exposure and performance on a comprehensive battery of neurocognitive, functional capacity, and informant-rated functional measures. The associations were adjusted for variation in sociodemographic indicators, psychopathologic symptoms, and substance use.

RESULTS

There was an average of 12 pack years of smoking across the sample. People with schizophrenia reported double the rate of current smoking compared to patients with bipolar disorder. Adjusting for demographic covariates, current smokers had worse composite cognitive functioning and poorer functional outcome than past or never smokers. There were no significant differences between never and past smokers, and these effects were evident in both bipolar disorder and schizophrenia.

CONCLUSION

Current smokers with either schizophrenia or bipolar disorder evidence worse cognitive and adaptive functioning functional outcome, even when demographic covariates are considered.

Prevalence, patterns, associated factors and severity of substance use among psychotic patients in southern Thailand

Co-occurring substance use in psychotic patients causes many subsequences including increased illness severity, decreased medication compliance, higher relapse rates, more hospitalizations, and legal problems. We aim to investigate the prevalence, patterns, associated factors and severity of substance use risk among psychotic patients in southern Thailand. Psychotic out-patients were screened with the Alcohol, Smoking, Substance Involvement Screening Test (ASSIST) for their history of substance use in the past three months and categorized as None-to-Low Risk (NLR) or Moderate-to-High Risk (MHR) levels. Multivariate logistic regression was used to examine the associated factors of substance use risk-level. The associations between substance use risk-level and emotional and behavioural symptoms, functional status and family functional status were examined using multivariate linear regression analysis. Of 663 participants screened, 322 (48.6%) used at least one substance in the past three months. Tobacco was the most common substance used (47.2%). The factors associated with a higher risk of any substance use were male gender, young age group, low level of education, being employed and being diagnosed with schizophrenia. A higher number of emotional and behavioural symptoms was significantly associated with higher substance use risk-level. In conclusion, the prevalence of substance use in psychotic patients was high and associated with their emotional and behavioural symptoms. Recommendations for implementation of screening and early intervention programs of substance-related problems in psychotic patients are important for preventing unwanted outcomes.

Modulation of auditory deviance detection by acute nicotine is baseline and deviant dependent in healthy nonsmokers: a mismatch negativity study

OBJECTIVE

Cognitive enhancement resulting from nicotinic acetylcholine receptor stimulation may be evidenced by increased efficiency of the auditory-frontal cortex network of auditory discrimination, which is impaired in schizophrenia, a cognitive disorder associated with excessive tobacco use. Investigating automatic (preattentive) detection of acoustic change with the mismatch negativity (MMN) brain event-related potential in response to nicotine in individuals with varying baseline levels of auditory discrimination may provide useful insight into the cholinergic regulation of this neural network and its potential amelioration with novel nicotinic agents.

METHODS

Sixty healthy, non-smoking male volunteers were presented with an 'optimal' multi-feature MMN paradigm in a randomized, placebo controlled double-blind design with 6 mg of nicotine gum.

RESULTS

Participants with low, medium, and high baseline amplitudes responded differently to nicotine (vs. placebo), and nicotine response was feature specific. Whereas MMN in individuals with high amplitudes was diminished by nicotine, MMN increased in those with low amplitudes. Nicotine effects were not shown in medium amplitude participants.

CONCLUSIONS

These findings provide preliminary support for the role of nicotinic neurotransmission in sensory memory processing of auditory change and suggest that nicotinic receptor modulation can both enhance and diminish change detection, depending on baseline MMN and its eliciting stimulus feature.

Neurocognitive endophenotypes in schizophrenia: modulation by nicotinic receptor systems

Cigarette smoking is the leading preventable cause of death in the Western world, with a considerably higher prevalence observed in schizophrenia compared to the general population. Despite the negative health consequences of smoking heavily, it has been proposed that individuals with schizophrenia may maintain smoking behaviors to remediate symptoms associated with the disorder. Neurocognitive deficits are a core feature of schizophrenia and are present in approximately 80% of patients. Further, these deficits constitute an endophenotype of schizophrenia, as they are stable across disease phases, and are heritable. The neurocognitive deficits that are present in schizophrenia are especially debilitating, since they are associated with poor clinical and functional outcomes and community integration. Interestingly, these deficits may also constitute a vulnerability factor towards the initiation and maintenance of tobacco use. Contributing to the potential shared vulnerability between schizophrenia and tobacco dependence is a dysregulation of the nicotinic acetylcholine receptor (nAChR) system. Pre-clinical evidence has shown that nicotine affects several neurotransmitter systems, including dopamine (DA), glutamate, and γ-aminobutyric acid (GABA), and certain neuropsychological deficits associated with these neurotransmitters (reaction time, spatial working memory, sustained attention, and sensory gating) are improved after nicotine administration in patients with schizophrenia. These positive effects on neurocognition appear to be more pronounced in smokers with schizophrenia, and may be an important mechanism that explains the co-morbidity of schizophrenia and tobacco dependence.

A longitudinal study of cognitive functioning in schizophrenia: clinical and biological predictors

BACKGROUND

Cognitive deficits are a central feature of schizophrenia but it is not certain how cognitive functioning changes over time. The purpose of this prospective longitudinal study was to determine the temporal change of cognitive functioning and the predictors of cognitive performance from among demographic, clinical, and biological variables.

METHODS

Participants were individuals with schizophrenia or schizoaffective disorder whose cognitive functioning was assessed at multiple time points with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). At the baseline visit participants had a blood sample drawn from which C-reactive protein, antibodies to Herpes Simplex Virus type 1, and selected genetic polymorphisms were measured. Repeated measures linear regression was used to determine whether cognitive measures changed over time and which variables predicted cognitive performance.

RESULTS

The sample consisted of 132 participants, mean age 43.7 years at baseline, who received a median of 3 cognitive assessments over a period averaging 2.8 years. The RBANS Total score and Language index showed no statistically significant temporal change; performance on two indices, Immediate Memory and Attention, showed modest but statistically significant improvements (gains of 0.89±0.33 and 0.76±0.29 points per year, respectively); Visuospatial/Constructional performance showed a modest but statistically significant decline (of 0.80±0.25 points per year). Few variables predicted cognitive performance; however greater psychiatric symptom severity was associated with worse cognitive performance for most cognitive measures.

CONCLUSIONS

Cognitive functioning in middle-aged persons with schizophrenia showed an absence of decline for most measures and modest gains in some measures.

Meta-analysis: the effects of smoking on the disposition of two commonly used antipsychotic agents, olanzapine and clozapine

OBJECTIVE

To clarify the effects of smoking on the disposition of two commonly used antipsychotics, olanzapine and clozapine, and to create standards to adjust the doses of these drugs in clinical practice based on the smoking status.

DESIGN

A meta-analysis was conducted by searching MEDLINE, Scopus and the Cochrane Library for relevant prospective and retrospective studies.

INCLUDED STUDIES

We included the studies that investigated the effects of smoking on the concentration to dose (C/D) ratio of olanzapine or clozapine.

PRIMARY OUTCOME MEASURE

The weighted mean difference was calculated using a DerSimonian-Laird random effects model, along with 95% CI.

RESULTS

Seven association studies, comprising 1094 patients (652 smokers and 442 non-smokers) with schizophrenia or other psychiatric disorders, were included in the meta-analysis of olanzapine. The C/D ratio was significantly lower in smokers than in non-smokers (p<0.00001), and the mean difference was -0.75 (ng/mL)/(mg/day) (95% CI -0.89 to -0.61). Therefore, it was estimated that if 10 and 20 mg/day of olanzapine would be administered to smokers, about 7 and 14 mg/day, respectively, should be administered to non-smokers in order to obtain the equivalent olanzapine concentration. Four association studies of clozapine were included in the meta-analysis of clozapine, comprising 196 patients (120 smokers and 76 non-smokers) with schizophrenia or other psychiatric disorders. The C/D ratio was significantly lower in smokers than in non-smokers (p<0.00001), and the mean difference was -1.11 (ng/mL)/(mg/day) (95% CI -1.53 to -0.70). Therefore, it was estimated that if 200 and 400 mg/day of clozapine would be administered to smokers, about 100 and 200 mg/day, respectively, should be administered to non-smokers.

CONCLUSIONS

We suggest that the doses of olanzapine and clozapine should be reduced by 30% and 50%, respectively, in non-smokers compared with smokers in order to obtain an equivalent olanzapine or clozapine concentration.