Smoking tobacco is associated with an increased risk of developing psychosis, such as schizophrenia, according to a new study published Friday in the Journal Lancet Psychiatry.

Researchers from King's College London conducted a meta-analysis of 61 observational studies comprising almost 15,000 tobacco users and 273,000 non users.

They analyzed rates of smoking in people presenting with their first episode of psychosis and found that 57 percent of these individuals were smokers.

The results also showed that daily smokers developed psychotic illness around a year earlier than non-smokers.

It is thought that activity within the brain's dopamine system might be one explanation of a possible causal link between smoking and psychosis, according to the study.

Excess dopamine is by far the best biological explanation for psychotic illnesses such as schizophrenia, and it is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop, said Prof. Robin Murray from King's College London.

But researchers also said longer-term studies are required to investigate the relationship between daily smoking, sporadic smoking, nicotine dependence and the development of psychotic disorders.