Effects of smoking history on selective attention in schizophrenia

Anticholinergic load: A commonly neglected and preventable risk to cognition during schizophrenia treatment?

Background

Cognitive impairment is a widespread feature of schizophrenia, affecting nearly 80 % of patients. Prior research has linked the anticholinergic burden of psychiatric medications to these cognitive deficits. However, the impact of the anticholinergic burden from medications for physical morbidity remains underexplored. This study aimed to evaluate the anticholinergic burden of psychiatric and physical medications in patients with schizophrenia and assess its impact on cognitive function.

Methods

A total of 178 patients with schizophrenia were recruited. The assessments included an ad hoc questionnaire for collecting demographic and clinical data. Anticholinergic burden was evaluated using the cumulative Drug Burden Index (cDBI) for each participant, and cognitive function was assessed using MATRICS. Psychopathology was measured using the PANSS, CDSS, CAINS, and the CGI-S. Statistical analysis included Student's t-tests, ANOVA, Pearson correlations, and multiple linear regressions.

Results

The average cDBI was 1.3 (SD = 0.9). The model developed explained 40.80 % of the variance. The variable with the greatest weight was the cDBI (B = -11.148, p = 0.010). Negative-expression (B = -2.740, p = 0.011) and negative-experiential (B = -1.175, p = 0.030) symptoms were also associated with lower global cognitive score. However, more years of education (B = 5.140, p < 0.001) and cigarettes per day (B = 1.331, p < 0.001) predicted a better global cognitive score.

Conclusion

This study identified specific predictors of global cognition in schizophrenia, with anticholinergic burden emerging as the strongest factor. Our findings underscore the importance of considering the anticholinergic burden of treatments, in addition to negative symptoms, when designing interventions to optimize or maintain cognitive function in patients with schizophrenia.

Smoking and attention in schizophrenia spectrum disorders: What are we neglecting?

Introduction

Individuals with schizophrenia spectrum disorders (SSDs) record elevated rates of smoking, which is often attributed to their effort to self-medicate cognitive and attentional symptoms of their illness. Empirical evidence for this hypothesis is conflicting, however. In this study, we aimed to test predictions derived from the cognitive self-medication hypothesis. We predicted that cigarette smoking status and extent would predict the attentional performance of participants with SSDs. Simultaneously, we wished to address methodological gaps in previous research. We measured distinct attentional components and made adjustments for the effects of other, attention-modulation variables.

Methods

Sixty-one smokers (82.0% males, 26.73 ± 6.05 years) and 61 non-smokers (50.8% males, 27.10 ± 7.90 years) with recent-onset SSDs completed an X-type Continuous Performance Test, which was used to derive impulsivity and inattention component scores. Relationships between the two component scores and cigarette smoking status and extent were assessed using hierarchical regression. Effects of estimated premorbid intellectual functioning and antipsychotic medication dosage were held constant.

Results

Smokers had significantly higher inattention component scores than non-smokers when covariates were controlled (p = 0.026). Impulsivity remained unaffected by smoking status (p = 0.971). Cigarette smoking extent, i.e., the number of cigarettes smoked per day, was not associated with either inattention (p = 0.414) or impulsivity (p = 0.079).

Conclusion

Models of smoking-related attentional changes can benefit from the inclusion of sample-specific component scores and attention-modulating covariates. Under these conditions, smokers with SSDs can show a partial attentional benefit. However, the limited scope of this benefit suggests that the cognitive self-medication hypothesis requires further testing or reconsidering.

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.

Worldwide prevalence of smoking cessation in schizophrenia patients: A meta-analysis of comparative and observational studies

Although the rate of cigarette smoking is high in schizophrenia patients, the prevalence of smoking cessation in this group is reportedly low. This meta-analysis aimed to examine the prevalence of cessation among schizophrenia patients worldwide. A systematic literature search in PubMed, PsycINFO, Medline, EMBASE, Cochrane Library and Web of Science was performed from their inception date until 15 November 2018. Studies that reported prevalence of smoking cessation were synthesized using a random-effects model. Fourteen studies were included. The pooled prevalence of smoking cessation among schizophrenia patients was 14.0 % (95 % CI: 9.2-18.8 %; I² = 97.3 %). Compared with schizophrenia patients, both healthy controls (OR = 0.45, 95 % CI:0.38-0.54, p < 0.001) and controls with other psychiatric disorders (OR = 0.79, 95 % CI:0.63-0.99, p = 0.004) had significantly higher prevalence of cessation. Subgroup and meta-regression analyses found that year of survey (after 2005), duration of smoking cessation (<6 months), outpatient setting and poor study quality were significantly associated with higher prevalence of smoking cessation. This meta-analysis found that the prevalence of smoking cessation was significantly lower among schizophrenia patients compared to healthy control and those with other psychiatric disorders. Better understanding of the barriers to smoking cessation and more effective measures for quitting smoking should be developed for patients with schizophrenia.

Sex differences in the cognitive function of first-diagnosed, drug-naïve depressed patients: An observational case-control study

BACKGROUND

Major depressive disorder (MDD) is a severe mental illness with high prevalence and recurrence rates. Cognitive impairments are found in most depressed patients, but systematic assessment of sex differences in cognitive deficits remains to be investigated.

METHODS

A total of 69 first-diagnosed, drug-naïve depressed outpatients (males/females = 28/41; average age: 27.51±8.82 years) and 57 healthy controls (HCs) (males/females = 26/31; average age: 29.05±8.69 years) were recruited. Cognitive function, measured by repeatable battery for the assessment of neuropsychological status [RBANS] scores, was compared between depressed patients and healthy controls in males and females.

RESULTS

Immediate memory, delayed memory and RBANS total score were significantly decreased in depressed patients compared with healthy controls. Moreover, among patients with first-diagnosed, drug-naïve depression, females had lower visuospatial and constructional scores than males, whereas among controls, females had higher language scores than males. Interestingly, impaired attention was negatively associated with the Beck Depression Inventory-II (BDI-II) score in female patients, but not in male patients.

CONCLUSION

Female patients with first-diagnosed, drug-naïve depression had more serious cognitive impairment than male patients in the visuospatial and constructional categories. Cognitive impairment was associated with depression severity only in female patients. These observations build the basis for future investigation of sex differences in cognitive impairment of depressed patients.

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.

Moderating effect of schizotypy on the relationship between smoking and neurocognition

Purpose

Smoking rates in schizotypic individuals are shown to be elevated, as in patients with schizophrenia, although findings on the association of smoking with different symptomatology of schizotypy have been mixed. Moreover, possible moderating effects of schizotypy on the relationship between smoking and cognition have not been well documented.

Subjects and methods

The Schizotypal Personality Questionnaire (SPQ) and the full version of the Wechsler Memory Scale-Revised (WMS-R) were administered to 501 healthy adults. Subjects were divided into smokers (n = 85) and non-smokers (n = 416) based on the presence/absence of current smoking.

Results

The analysis of covariance (ANCOVA) on the three factor scores as well as the total score of the SPQ, controlling for age and gender, revealed that cognitive-perceptual factor was significantly associated with an increased rate of smoking (P = 0.048). The ANCOVA on the WMS-R indices, with smoking group as a fixed factor and age, gender and total SPQ score as covariates, revealed that the schizotypy-by-smoking interaction was significant for attention/working memory (P = 0.029).

Discussion and conclusion

Positive schizotypy may be associated with more smoking. Schizotypy and smoking could interact with each other to negatively affect attention/working memory.

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).

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.

Smoking does not impact social and non-social cognition in patients with first episode psychosis

BACKGROUND

Many studies having shown significant improvements in non-social and social cognitive performance in smoking FEP patients compared to non-smoking FEP patients. The findings are controversial. This study analyzed the effects of tobacco use on non-social and social cognitive function in a large group of FEP patients and a matched healthy control group.

METHODS

A sample of 335 patients with FEP and 253 healthy controls was divided into four subgroups: control tobacco users (CTU), control non-tobacco users (CNTU), patient tobacco users (PTU) and patient non-tobacco users (PNTU). Demographic variables, tobacco use variables (presence or absence, frequency and duration of tobacco use), neurocognitive (non-social) performance and social cognition were assessed.

RESULTS

Comparison of 4 subgroups in non-social cognitive function revealed significant differences after controlling for covariables in executive functions (F=13.45; p≤0.001) and working memory domains (F=4.30; p=0.005). CTU and CNTU subgroups scored higher in all the domains compared to the PTU and the PNTU subgroups respectively. Social cognitive function was also significantly different within the four subgroups, with control subgroups showing better social cognition than patient subgroups. Significant differences in the executive functions domain were observed when comparing PTU and CTU groups (F=19.60; p≤0.001). No significant differences were revealed in the comparison between the patient groups.

CONCLUSIONS

This large study suggests that tobacco use in FEP patients is not related to better non-social or social cognitive performance.

Nicotine self-administration reverses cognitive deficits in a rat model for schizophrenia

High comorbidity between schizophrenia and tobacco addiction has been well established. Explanatory theories include nicotine as a cognitive enhancer ameliorating symptoms of schizophrenia and underlying shared substrates increasing susceptibility to addiction in these individuals. To test these non-mutually exclusive theories, the maternal immune activation (MIA) model was utilized. To this end, pregnant Sprague Dawley rats were subcutaneously injected with a bacterial endotoxin, lipopolysaccharide (0.5 mg/kg), on gestation days 10 and 11. Selective attention and working memory in adult male offspring were subsequently assessed using the latent inhibition and delayed non-matching to sample paradigms both before and after nicotine or saline self-administration. MIA led to deficits in both latent inhibition and delayed non-matching to sample in male offspring. Further, these animals showed a small but significantly increased responding for nicotine during self-administration acquisition, although there was no difference in dose-response effect or in progressive ratio testing. However, nicotine, but not saline self-administration, significantly ameliorated the cognitive deficits induced by MIA. While the male offspring of mothers prenatally exposed to lipopolysaccharide was only slightly more sensitive to the reinforcing effects of nicotine, after self-administration, the MIA-induced cognitive deficits significantly improved. These data lend support for the self-medication hypothesis of schizophrenia.

Neurophysiological Characterization of Attentional Performance Dysfunction in Schizophrenia Patients in a Reverse-Translated Task

Attentional dysfunction in schizophrenia (SZ) contributes to the functional deficits ubiquitous to the disorder. Identifying the neural substrates of translational measures of attentional dysfunction would prove invaluable for developing therapeutics. Attentional performance is typically assessed via continuous performance tasks (CPTs), though many place additional cognitive demands with little cross-species test-relevance. Herein, event-related potentials (ERPs) were used to investigate the neurophysiological correlates of attention and response inhibition of SZ and healthy participants, whereas they performed the cross-species-translated five-choice CPT (5C-CPT). Chronically ill, medicated SZ patients and matched controls (n=25 SZ and 26 controls) were tested in the 5C-CPT, in conjunction with ERP and source localization assessments. The ERPs generated in response to correctly identified target and non-target trials revealed three peaks for analysis, corresponding to sensory registration (P₁), response selection (N₂), and response action (P₃). Behavioral responses revealed that SZ patients exhibited impaired attention driven by impaired and slower target detection, and poorer cognitive control. ERPs revealed decreased N₂ amplitudes reflecting poorer response selection for both target and non-target trials, plus reduced non-target P₃s in SZ patients, the latter accounting for 37% of variance in negative symptoms. Source analyses revealed that the brain regions of significant differences localized to the left dorsolateral prefrontal cortex during response selection and the posterior cingulate cortex for cognitive processes. SZ patients exhibited impaired attention and cognitive control, characterized by less robust frontal and parietal ERP distributions across the response selection and cognitive response time windows, providing neurophysiological characterization of attentional dysfunction in SZ using the reverse-translated 5C-CPT.

Cognitive neuropsychological functioning in New Zealand Māori diagnosed with schizophrenia

OBJECTIVE

Previous research suggests that New Zealand Māori may have an elevated rate of schizophrenia. However, there is limited evidence on important clinical features of the illness in this population. This study examined cognitive neuropsychological functioning in 54 adult Māori diagnosed with schizophrenia and 56 Māori controls. This study also examined associations between cognition, medication and symptoms of psychosis in the schizophrenia group.

METHOD

The groups were matched on socio-demographic variables, handedness and premorbid cognitive ability. Participants were assessed on neuropsychological tests of attention, executive ability, motor, premorbid ability, verbal/non-verbal memory and verbal fluency (English/Māori versions). The Positive and Negative Syndrome Scale was used to assess psychotic symptoms. Information on cultural identity, duration of illness, duration of untreated psychosis, medication and substance abuse was collected.

RESULTS

The performance of the schizophrenia group was significantly lower than the control group on all the neuropsychological tests, except the test of attention. The effect sizes were moderate to large: 0.78 for motor function; 1.3 for executive ability, verbal fluency and visual memory; 1.6 for verbal learning and 1.8 for verbal memory. These differences remained after adjustment for multiple comparisons and covariates. A higher dose of antipsychotic medication and a higher anticholinergic load were associated with greater verbal memory impairment (r = -0.38 and r = -0.38, respectively). A longer duration of illness was associated with greater impairment of verbal memory (rho = -0.48), verbal learning (rho = -0.41) and visual memory (rho = -0.44).

CONCLUSION

The findings for the schizophrenia group show a profile of generalised cognitive impairment with greater impairment of verbal memory. The cognitive impairment in this group was independent of psychotic symptoms, but was associated with a higher antipsychotic dose, higher anticholinergic load and longer duration of illness. These findings have implications for clinical prescribing practices and rehabilitation for New Zealand Māori diagnosed with schizophrenia.

Nicotine ameliorates schizophrenia-like cognitive deficits induced by maternal LPS exposure: a study in rats

Maternal exposure to infectious agents is a predisposing factor for schizophrenia with associated cognitive deficits in offspring. A high incidence of smoking in these individuals in adulthood might be, at least in part, due to the cognitive-enhancing effects of nicotine. Here, we have used prenatal exposure to maternal lipopolysaccharide (LPS, bacterial endotoxin) at different time points as a model for cognitive deficits in schizophrenia to determine whether nicotine reverses any associated impairments. Pregnant rats were treated subcutaneously with LPS (0.5 mg/kg) at one of three neurodevelopmental time periods [gestation days (GD) 10-11, 15-16, 18-19]. Cognitive assessment in male offspring commenced in early adulthood [postnatal day (PND) 60] and included: prepulse inhibition (PPI), latent inhibition (LI) and delayed non-matching to sample (DNMTS). Following PND 100, daily nicotine injections (0.6 mg/kg, subcutaneously) were administered, and animals were re-tested in the same tasks (PND 110). Only maternal LPS exposure early during fetal neurodevelopment (GD 10-11) resulted in deficits in all tests compared to animals that had been prenatally exposed to saline at the same gestational time point. Repeated nicotine treatment led to global (PPI) and selective (LI) improvements in performance. Early but not later prenatal LPS exposure induced consistent deficits in cognitive tests with relevance for schizophrenia. Nicotine reversed the LPS-induced deficits in selective attention (LI) and induced a global enhancement of sensorimotor gating (PPI).

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.

Smoking in schizophrenic patients: A critique of the self-medication hypothesis

A common remark among laypeople, and notably also among mental health workers, is that individuals with mental illnesses use drugs as self-medication to allay clinical symptoms and the side effects of drug treatments. Roots of the self-medication concept in psychiatry date back at least to the 1980s. Observations that rates of smokers in schizophrenic patients are multiple times the rates for regular smoking in the general population, as well as those with other disorders, proved particularly tempting for a self-medication explanation. Additional evidence came from experiments with animal models exposed to nicotine and the identification of neurobiological mechanisms suggesting self-medication with smoking is a plausible idea. More recently, results from studies comparing smoking and non-smoking schizophrenic patients have led to the questioning of the self-medication hypothesis. Closer examination of the literature points to the possibility that smoking is less beneficial on schizophrenic symptomology than generally assumed while clearly increasing the risk of cancer and other smoking-related diseases responsible for early mortality. It is a good time to examine the evidence for the self-medication concept as it relates to smoking. Our approach is to focus on data addressing direct or implied predictions of the hypothesis in schizophrenic smokers.

Small effects of smoking on visual spatiotemporal processing

Nicotine is an important stimulant that is involved in modulating many neuronal processes, including those related to vision. Nicotine is also thought to play a key role in schizophrenia: A genetic variation of the cholinergic nicotine receptor gene, alpha-7 subunit (CHRNA7) has been shown to be associated with stronger backward masking deficits in schizophrenic patients. In this study, we tested visual backward masking in healthy smokers and non-smokers to further understand the effects of nicotine on spatiotemporal vision. In the first study, we tested 48 participants, a group of non-smokers (n = 12) and three groups of regular smokers that were either nicotine deprived (n = 12), non-deprived (n = 12) or deprived but were allowed to smoke a cigarette directly before the start of the experiment (n = 12). Performance was similar across groups, except for some small negative effects in nicotine-deprived participants. In the second study, we compared backward masking performance between regular smokers and non-smokers for older (n = 37, 13 smokers) and younger (n = 67, 21 smokers) adults. Older adults performed generally worse than younger adults but there were no significant differences in performance between smokers and non-smokers. Taken together, these findings indicate that nicotine has no long-term negative effects on visual spatiotemporal processing as determined by visual backward masking.

Smoking improves divided attention in schizophrenia

RATIONALE

Smoking is highly prevalent in schizophrenia, and there is evidence for beneficial effects on neurocognition. Smoking is therefore hypothesized a self-medication in schizophrenia. Although much effort is devoted to characterize those cognitive domains that potentially benefit from smoking, divided attention has not yet been investigated.

OBJECTIVES

The aim of this study was to analyze the interactional effects of diagnosis of schizophrenia and smoking history on divided attention.

METHODS

We investigated behavioral measures of divided attention in a sample of 48 schizophrenic patients and 48 controls (24 current smokers and non-smokers each) carefully matched for age, sex, education, verbal IQ, and smoking status with general linear models.

RESULTS

Most important within the scope of this study, significant interactions were found for valid reactions and errors of omission: Performance substantially increased in smoking schizophrenic patients, but not in controls. Further, these interactions were modified by sex, driven by female schizophrenic patients who showed a significant behavioral advantage of smokers over non-smokers, other than male schizophrenic patients or healthy controls who did not express this sex-specific pattern.

CONCLUSIONS

Results suggest a positive effect of smoking history on divided attention in schizophrenic patients. This study provides first evidence that the complex attention domain of divided attention is improved by smoking, which further substantiates the self-medication hypothesis of smoking in schizophrenia, although this has been shown mainly for sustained and selective attention. Gender-specific effects on cognition need to be further investigated.

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

BACKGROUND AND OBJECTIVES

Compared to the general population cigarette smoking prevalence is elevated in psychiatric disorders such as schizophrenia (SZ), bipolar disorder (BD), and major depressive disorder (MDD). These disorders are also associated with neurocognitive impairments. Cigarette smoking is associated with improved cognition in SZ. The effects of smoking on cognition in BD and MDD are less well studied.

METHODS

We used a cross-sectional design to study neuropsychological performance in these disorders as a function of smoking status. Subjects (N = 108) were SZ smokers (n = 32), SZ non-smokers (n = 15), BD smokers (n = 10), BD non-smokers (n = 6), MDD smokers (n = 6), MDD non-smokers (n = 10), control smokers (n = 12), and control non-smokers (n = 17). Participants completed a neuropsychological battery; smokers were non-deprived.

RESULTS

SZ subjects performed significantly worse than controls in select domains, while BD and MDD subjects did not differ from controls. Three verbal memory outcomes were improved in SZ smokers compared with non-smokers; smoking status did not alter performance in BD or MDD.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

These data suggest that smoking is associated with neurocognitive improvements in SZ, but not BD or MDD. Our data may suggest specificity of cigarette-smoking modulation of neurocognitive deficits in SZ.

Cigarette smoking modulates medication-associated deficits in a monetary reward task in patients with schizophrenia

Imaging studies of reward processing have demonstrated a mesolimbic-mesocortical dopaminergic dysfunction in schizophrenia. Such studies on reward processing in patients and also in healthy controls showed that differential activations of dopaminergic brain areas are associated with adaptive changes in response speed related to different reward values. Given this relationship, we investigated reward processing on the behavioural level in a larger sample of 49 medicated patients with a diagnosis of schizophrenia (ICD-10 F20) and 49 healthy controls. Subjects were instructed to react by button press upon two different stimuli in order to retain a 60 % chance winning a previously announced high (1$) or low (20¢) amount of money paid to participants after the experiment. Concordant with previous reports on deficits in reward processing, acceleration of reaction times in patients upon low rewards differed significantly (p < 0.05) from healthy controls in our present behavioural study. This effect was pronounced in the non-smoking subgroup of patients (n = 24). In this subgroup, we also observed a significant (p < 0.05) positive correlation with medication type (relatively high vs. low D2 receptor affinity) and with the PANSS score, the latter with a trend to significance (p = 0.08). Our study demonstrates that reaction time measures in a monetary reward task might constitute a feasible behavioural proxy for dopaminergic dysfunction and its different dimensions regarding psychopathology but also medication in patients with schizophrenia. In line with clinical observations, our findings support the notion that smoking modulates medication-associated side effects on reward processing in patients with schizophrenia.

Comparison of the effectiveness of Conners' CPT and the CPT-identical pairs at distinguishing between smokers and nonsmokers with schizophrenia

Sustained attention deficits and high rates of smoking are often observed in patients with schizophrenia. This has led to the hypothesis that patients may smoke as an attempt to ameliorate cognitive deficits related to abnormal nicotinic structure and function. Continuous performance tasks (CPT) are often used to index sustained attention deficits in patients with schizophrenia, however, there are important differences between tasks that may impact performance in smokers and nonsmokers with schizophrenia differently. The Conners' CPT (C-CPT) has a high signal-to-noise ratio and is commonly used to assess impulsivity. The CPT-Identical Pairs (CPT-IP) has a low signal-to-noise ratio and is commonly used to assess negative symptoms in patients with schizophrenia. We sought to determine whether there were differences of sustained attention between patient smokers vs. nonsmokers, and if one CPT would provide a better separation of sustained attention between groups. Results revealed that both instruments detect more impaired sustained attention deficits in patient smokers compared to nonsmokers. Patient smokers performed significantly worse on the majority of the CPT-IP composite scores compared to the C-CPT composite scores. These results do not support the self-medication theory, as patient smokers performed worse than patient nonsmokers. Researchers studying sustained attention in schizophrenia may wish to consider the CPT-IP over the C-CPT, as well as control for smoking status.

Gender differences in cognitive function of patients with chronic schizophrenia

Schizophrenic patients have cognitive impairments, but gender differences in these cognitive deficits have had limited study. This study assessed cognitive functioning in 471 subjects including 122 male and 78 female schizophrenic patients and 141 male and 130 female healthy controls. We found that immediate memory, language, delayed memory and total RBANS scores were significantly decreased in schizophrenia compared with healthy controls for both genders. Male patients had significant lower immediate memory, delayed memory and total RBANS scores than female patients, and healthy controls showed a similar gender difference. The RBANS showed modest correlations with PANSS scores, duration of illness and antipsychotic dose (chlorpromazine equivalents). Almost all RBANS scores in the schizophrenics and healthy controls showed significant positive correlations with education. Thus, patients of both sexes with schizophrenia experienced more deteriorated performance than healthy controls on cognitive domains of immediate memory, language and delayed memory. Furthermore, male schizophrenic patients had more serious cognitive deficits than female patients in immediate and delayed memory, but not in language, visuospatial and attention indices.