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Does smoking tobacco increase the risk of psychosis?

It has been acknowledged that individuals with psychosis tend to smoke more than the general population. This increased smoking tendency was assumed to be for a self-medicating purpose - to help with symptoms, impaired thinking and potentially counter the side effects of antipsychotic drugs. However, researchers at King’s College London have suggested that tobacco could play a part in causing schizophrenia.

The researchers, from King’s College London, have recently published a literature review demonstrating 57% of individuals arriving at mental health services with first episode psychosis were smokers. Also, in general, smokers who are at-risk of developing psychosis experience psychosis one year earlier than non-smokers. This may therefore suggest smoking may be a causal factor in itself.

However, there have already been criticisms to this paper. Such as, some of the studies did not account for cannabis use, which is a more accepted influence of psychosis. Additionally, a start point of the development of psychosis is not clear within the literature and it may be that a first-episode of psychosis is a result of a long-term deterioration of mental state prior to smoking.

An article in the Guardian suggests there are biologically plausible reasons as to why smoking may be linked to psychosis. For example, excessive dopamine is a biological explanation for psychosis and it is possible that nicotine exposure, by increasing the release of dopamine, increases the likelihood of psychosis developing. However, although the dopamine theory is a commonly held theory within psychosis, we are still unsure how dopamine influences psychosis.

This literature review has highlighted interesting connections between psychosis and smoking. Although this study does not determine the direction of cause (e.g. whether smoking or psychosis appeared first), this study gives good reasons to target public health measures at individuals who may have psychosis or at risk mental state.

By: Abigail Christine Wright
Last updated: Wednesday, 15 July 2015