Exogenous nicotine normalises sensory gating in schizophrenia; therapeutic implications

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.

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.

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.

C-Reactive Protein as a Peripheral Biomarker in Schizophrenia. An Updated Systematic Review

Objectives: The objective of this systematic review was to synthetize the published data on the relationships between elevated blood C-reactive protein (CRP) levels and schizophrenia (SZ) onset risk, illness characteristics and treatments, cognition and physical health. Method: The systematic bibliographic searches have been carried out according to the Cochrane methodology. Medline, web of science, Google Scholar with each database being searched from inception to November 2017. Results: 53 studies were included in the present review. While meta-analyses including case-control studies suggest a clear association between CRP and SZ, one other study has suggested that CRP-associated genes were associated with a lower risk of SZ onset. Increased CRP has been significantly associated with positive symptoms in acute phase psychosis, while studies including community-dwelling stabilized subjects did not find such an association. Abnormal CRP has been associated with a wide range of cognitive impairment in SZ stabilized individuals. Body Mass index has been extensively associated with increased CRP in SZ subjects; and increased CRP has been identified as a risk factor for metabolic syndrome and cardiovascular risk in SZ subjects. Increased CRP has also been associated with high nicotine dependence in SZ smokers and one study has suggested that increased CRP was associated with sedentary behavior. Conclusion: In the light of the above-mentioned studies, increased hs-CRP may be reasonably suggested as a marker for SZ onset risk, as well as a risk factor for increased positive symptoms, cognitive impairment, hypovitaminosis D, microbiota disturbances, cardiovascular and metabolic syndrome risk in SZ subjects, and increased nicotine dependence in SZ smokers. In case of increased CRP levels, anti-inflammatory strategies (add-on anti-inflammatory drugs including aspirin and omega 3 fatty acids, vitamin D supplementation, physical activity, probiotics) should be also further evaluated. Limits: Most of the studies were cross-sectional and cohort studies are needed to determine the temporal relationship between increased CRP and the psychiatric outcomes.

Chronic low-grade peripheral inflammation is associated with severe nicotine dependence in schizophrenia: results from the national multicentric FACE-SZ cohort

Chronic peripheral inflammation (CPI) has been associated with cognitive impairment in schizophrenia (SZ). However, its sources remain unclear, more specifically it is not known whether tobacco smoking is a source of inflammation or not in SZ subjects. Moreover, nicotine (NIC), the major psychoactive compound of tobacco, shows strong anti-inflammatory properties in vitro, as well as inducing a severe biological dependence when administered repeatedly. The objective of the present study was to determine if CPI was associated with tobacco smoking and/or NIC dependence in schizophrenia. Three hundred and forty five stabilized community-dwelling SZ subjects aged 16 years or older (mean age = 32 years, 73% male) were consecutively included in the network of the FondaMental Expert Centers for Schizophrenia and assessed with validated scales. CPI was defined by a highly sensitive C-reactive protein (hsCRP) ≥3 mg/L. Current tobacco status was self-declared. Severe NIC dependence was defined by a Fagerstrom Test for Nicotine Dependence score ≥7. Overall, 159 (46.1%) were non-smokers, 117 (33.9%) and 69 (20%) were current tobacco smokers with, respectively, low and severe nicotine dependence. In a multivariate model, CPI remained associated with severe NIC dependence (29 vs 15%, OR = 2.8, p = 0.003) and body mass index (OR = 1.1, p < 0.0001), independently of socio-demographic characteristics and antidepressant intake. No association of CPI with low to moderate tobacco smoking dependence, number of daily smoked cigarettes, cannabis use, alcohol use or illness characteristics was found (all p > 0.05). CPI was associated with severe NIC dependence but not with tobacco smoking with low to moderate NIC dependence in SZ, independently of socio-demographic variables, body mass index, alcohol consumption and antidepressant intake. This result highlights the potential CPI consequences of the high prevalence of heavy tobacco smoking in SZ, indicating the importance of new therapeutic strategies for tobacco cessation in SZ.

The negative affect hypothesis of noise sensitivity

Some studies indicate that noise sensitivity is explained by negative affect, a dispositional tendency to negatively evaluate situations and the self. Individuals high in such traits may report a greater sensitivity to other sensory stimuli, such as smell, bright light and pain. However, research investigating the relationship between noise sensitivity and sensitivity to stimuli associated with other sensory modalities has not always supported the notion of a common underlying trait, such as negative affect, driving them. Additionally, other explanations of noise sensitivity based on cognitive processes have existed in the clinical literature for over 50 years. Here, we report on secondary analyses of pre-existing laboratory (n = 74) and epidemiological (n = 1005) data focusing on the relationship between noise sensitivity to and annoyance with a variety of olfactory-related stimuli. In the first study a correlational design examined the relationships between noise sensitivity, noise annoyance, and perceptual ratings of 16 odors. The second study sought differences between mean noise and air pollution annoyance scores across noise sensitivity categories. Results from both analyses failed to support the notion that, by itself, negative affectivity explains sensitivity to noise.

Baseline dependency of nicotine's sensory gating actions: similarities and differences in low, medium and high P50 suppressors

Reduced suppression of the P50 auditory event-related potential in schizophrenia patients relative to normal controls is indicative of a sensory gating deficit and is one of the most robust findings reported for functional brain abnormalities in this disorder. However, there is considerable gating variability in patients and controls and there is little understanding as to how inter-individual differences moderate gating responses to drugs and nicotinic agonists in particular, which have shown potential to reverse gating deficits. In this study the effects of acutely administered nicotine (gum, 6 mg) on sensory gating in a paired (S₁-S₂) auditory stimulus paradigm were investigated in 57 healthy, non-smoking volunteers stratified as low (n = 19), medium (n = 19) and high (n = 19) P50 suppressors on the basis of three separate baseline derived gating indices, P50 ratios, P50 difference scores, and gating difference waveforms. Relative to placebo, nicotine consistently improved gating in low suppressors as stratified with all three gating indices, exerted no effects in medium suppressors and reduced gating in high suppressors. Analysis of individual stimulus (S₂, S₂) amplitudes showed distinctly different mechanisms of action underlying nicotine effects in individuals with low and high baseline suppression. The results parallel similar findings of baseline-dependency in the gating effects of several antipsychotic drugs in healthy volunteers and support the use of group segmentation as a translational model in novel cognitive drug development for schizophrenia.

Can genetics inform the management of cognitive deficits in schizophrenia?

There is no doubt that schizophrenia has a significant genetic component and a number of candidate genes have been identified for this debilitating disorder. Of note, several of these are implicated in cognition. Cognitive deficits constitute core symptoms of schizophrenia, and while current antipsychotic treatment strategies aim to help psychosis-related symptomatology, the cognitive symptom domain is largely inadequately treated. A number of other pharmacological approaches (e.g. using drugs that target specific neurotransmitter systems) have also been attempted for the amelioration of cognitive deficits in this population; however, these too have had limited success so far. Psychological interventions appear promising, though there has been speculation regarding whether or not these produce long-term functional improvements. Pharmacogenetic studies of the cognitive effects of currently available antipsychotics, although in relatively early stages, suggest that the treatment of cognitive deficits in schizophrenia may be advanced by focusing on genetic variants associated with specific cognitive dysfunctions in the general population and using this to match the most relevant pharmacological and/or psychological interventions with the genetic and cognitive profiles of the target population. Such a strategy would encourage bottom-up advances in drug development and provide a platform for individualised treatment of cognitive deficits in schizophrenia.

Nonmedication smoking reduction program for inpatients with chronic schizophrenia: a randomized control design study

People with schizophrenia are more likely to smoke, and to smoke more frequently, than those without schizophrenia. Furthermore, inpatients smoke even more frequently compared with those living in the community. In light of this, we implemented and assessed a smoking reduction intervention using a wide array of behavioral group techniques and methods in chronic hospitalized schizophrenic clients. Using a controlled design, we randomly assigned chronic schizophrenic clients to either a five-session smoking reduction intervention (n = 35) or a waiting list (WL; n = 18). We assessed self-reported smoking behavior, clinical status (Positive and Negative Syndrome Scale, Hamilton Rating Scale for Depression; Clinical Global Impression Scale for Psychosis), subjective quality of life (Quality of Life Enjoyment and Satisfaction Questionnaire-abbreviated version), and weight before and 3 months after the intervention. The intervention successfully reduced the number of cigarettes smoked compared with nonintervention. No clinical worsening or weight gain was observed. Behavioral group-oriented smoking reduction interventions can significantly reduce smoking behavior in hospitalized chronic clients with schizophrenia.

Cigarette smoking in patients with schizophrenia in China: prospective, multicentre study

OBJECTIVE

The aim of the present study was to explore the rate of cigarette smoking and its sociodemographic and clinical characteristics in Chinese schizophrenia patients.

METHODS

In a multicentre, randomized, controlled, longitudinal study, 374 clinically stable patients with schizophrenia were interviewed at entry using standardized assessment instruments, and followed up for 1-2 years.

RESULTS

The rate of cigarette smoking was 13.9% in the whole sample, and 26.2% in men and 3.5% in women. On univariate analysis, male sex, unemployment, alcohol consumption, older age, older age at onset, longer duration of illness, more frequent admissions, more severe hostility-excitement at entry and less deterioration in hostility-excitement over the study period were significantly associated with cigarette smoking. On multivariate analysis, male sex, unemployment, alcohol consumption, more frequent admissions, less severe positive and negative symptoms at entry, smaller decline in negative symptoms and more deterioration in disorganized thoughts over the study period were independently associated with cigarette smoking.

CONCLUSION

The rate of cigarette smoking in Chinese schizophrenia patients is considerably lower than most figures reported in the Western literature.