Does tobacco use cause psychosis? Systematic review and meta-analysis

Abstract

SummaryBackgroundAlthough the association between psychotic illness and cigarette smoking is well known, the reasons are unclear why people with psychosis are more likely to smoke than are the general population. We aimed to test several hypotheses. First, that daily tobacco use is associated with an increased risk of psychotic illness in both case-control and prospective studies. Second, that smoking is associated with an earlier age at onset of psychotic illness. Finally, that an earlier age at initiation of smoking is associated with an increased risk of psychosis. We also aimed to derive an estimate of the prevalence of smoking in patients presenting with their first episode of psychosis.MethodsWe searched Embase, Medline, and PsycINFO and selected observational studies in which rates of smoking were reported in people with psychotic disorders, compared with controls. We calculated the weighted mean difference for age at onset of psychosis and age at initiation of smoking. For categorical outcomes, we calculated odds ratios from cross-sectional studies and risk ratios from prospective studies.FindingsOf 3717 citations retrieved, 61 studies comprising 72 samples met inclusion criteria. The overall sample included 14 555 tobacco users and 273 162 non-users. The prevalence of smoking in patients presenting with their first episode of psychosis was 0·57 (95% CI 0·52–0·62; p<0·0001). In case-control studies, the overall odds ratio for the first episode of psychosis in smokers versus non-smokers was 3·22 (95% CI 1·63–6·33), with some evidence of publication bias (Egger's test p=0·018, Begg's test p=0·007). For prospective studies, we calculated an overall relative risk of new psychotic disorders in daily smokers versus non-smokers of 2·18 (95% CI 1·23–3·85). Daily smokers developed psychotic illness at an earlier age than did non-smokers (weighted mean difference −1·04 years, 95% CI −1·82 to −0·26). Those with psychosis started smoking at a non-significantly earlier age than did healthy controls (−0·44 years, 95% CI −1·21 to 0·34).InterpretationDaily tobacco use is associated with increased risk of psychosis and an earlier age at onset of psychotic illness. The possibility of a causal link between tobacco use and psychosis merits further examination.FundingNIHR Maudsley Biomedical Research Centre.

Substance use, medication adherence and outcome one year following a first episode of psychosis

“…Although nicotine dependence appears to be a risk factor for psychosis (Gurillo et al, 2015) and a predictor of worse clinical and social outcome in psychosis patients (Krishnadas et al, 2012), why this should be is still unclear (Gurillo et al, 2015;Krishnadas et al 2012). One possibility is that chronic nicotine use dysregulated dopamine signaling (Brody et al, 2010).…”

“…In addition, the relation of poor adherence to tobacco smoking has not to date been investigated. This is important given that tobacco smoking is highly prevalent among psychotic patients, and there have been recent suggestions that tobacco smoking may be a risk factor for both onset (Gurillo et al, 2015) and outcome (Krishnadas et al, 2012) of psychosis.…”

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“…Examining change in research outputs in this field is particularly important given recent high-profile publications identifying smoking and mental illness as a priority area for increased research attention. 20,21,44,45 The current study was conducted to describe the volume and characteristics (data-based, study type, study population, and study setting) of research publications in the field of smoking and mental illness across three time periods. For intervention-focused research, the level of evidence and phase of research translation were also considered; as indications of progress in the quality of research and the potential for population level impact respectively.…”