Cigarette smoking is already linked to multiple deadly diseases – including increased risks of GIT cancers and life-threatening lung cancers – now add Schizophrenia to that unending list. Smoking cigarettes, research says, can increase people’s risk of psychosis, who believe that tobacco as well as cannabis play a significant role in the development of schizophrenia. Daily smokers have an increased risk of psychosis, according to researchers. More than half – 57% – of people arriving at mental health services with their first episode were smokers, which is nearly three times the normal occurrence in the population. Also, to be noted, smokers experienced psychosis one year earlier than non-smokers.
Scientists already know for a fact that people suffering from psychosis tend to smoke more than most of the population, but it was taken in the category of self-medication and self soothing. “Having psychosis is a very distressing thing – hearing voices, having delusions,” said Dr James MacCabe from King’s Institute of Psychiatry, Psychology and Neuroscience, one of the authors of a new study.
“The argument goes, why wouldn’t people smoke to alleviate the distress?” They might hope it would help with the symptoms and their impaired thinking processes and possibly counter the side-effects of antipsychotic drugs, he said.
However, now an analysis of a number of studies on smoking tobacco and psychosis – published in the Lancet Psychiatry journal – has revealed that smoking may be a contributing factor to schizophrenia.
“We can’t say that we have proof that cigarette smoking causes schizophrenia,” said Sir Robin Murray, professor of psychiatric research at King’s. “Indeed it is very difficult to point to any particular factor and say it causes schizophrenia. It is a bit like heart disease – there are a number of risk factors. You inherit some vulnerability and … are exposed to various things which increase the risk to your life.”
Interestingly, there are many biological reasonings as to why smoking may be linked to psychosis. “Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia,” said Murray. “It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.” A number of other drugs can stimulate dopamine production, including amphetamines, cocaine and cannabis.
There are also genetic clues – a small number of DNA sequences (called SNPs) are known to be implicated in both schizophrenia and smoking.
“While it is always hard to determine the direction of causality, our findings indicate that smoking should be taken seriously as a possible risk factor for developing psychosis, and not dismissed simply as a consequence of the illness,” said MacCabe.
Prof Michael Owen, director of the Institute of Psychological Medicine and Clinical Neurosciences at Cardiff University, said this paper, together with a previous study carried out in Sweden, “make a pretty strong case that smoking is of causal relevance to schizophrenia”.
He hoped that more genetic investigation might help reveal the answers to this complicated web. “The fact is that it is very hard to prove causation without a randomized trial, but there are plenty of good reasons already for targeting public health measures very energetically at the mentally ill,” he said.