The nicotine in cigarette smoke may cause brain changes which actually increase the risk of developing schizophrenia by two fold the BBC reports based on research from a team at Kings College London who reported in The Lancet Psychiatry.

While the incidence of schizophrenia is 1 in 100, smoking may double the incidence to two in one hundred.

This was a meta-study which analyzed 61 published studies. Referring to this type of study, lead researcher Dr. James McCabe stated, “It’s very difficult to establish causation. What we’re hoping that this does is really open our eyes to the possibility that tobacco could be a causative agent in psychosis. We hope this will then lead to other research and clinical trials that would help to provide firmer evidence.” Dr. MacCabe works in the  Institute of Psychiatry, Psychology and Neuroscience at King’s College London.

It is already largely accepted in the research and treatment communities that persons with psychosis are more prone to smoke and it has been widely assumed that smoking was a method of self-medicating as the patients report decreases in symptoms such as hallucinations.

Researchers found that 57% of people with psychosis were smokers prior to their first psychotic episode.  Moreover, smokers developed schizophrenia a year earlier than non-smoking schizophrenics. These startling correlation data gives rise to the role nicotine may play in the causation of schizophrenia.

This theory is further bolstered by the researchers’ determination that daily smokers were twice as likely to develop schizophrenia as their non-smoking counterparts.

The data indicates that the brain chemical alteration centers on dopamine changes. It has previously been established that nicotine alters dopamine. The causation theory this raises is based on the widely reported data that indicates nicotine impacts psychosis. The new research begs for more investigation to confirm or deny that in some people — perhaps those with an existing predisposition to schizophrenia–nicotine triggers a dopamine alteration leading to schizophrenia.

Note that scientists are not suggesting that smoking alone causes schizophrenia. However, future findings may have further effect public policy on smoking.