Schizophrenia Linked to Smoking Cigarettes


An increased risk of developing schizophrenia and psychosis has been linked to smoking cigarettes by a recent study published in The Lancet Psychiatry, an online journal. The lead author of the study, which was conducted by a team of psychiatric researchers from King’s College London, was Sameer Jauhar.

Psychiatric researchers have been struck by the relationship between smoking and schizophrenia in the past, but no actual link had been searched for between smoking and mental illness until relatively recently. Jauhar stated in a podcast that “you always see patients with psychotic illnesses smoking.” He added that the relationship had been considered to be possibly an effort by schizophrenics at “self-medication.”

However, the research that the team from King’s College London conducted found that, rather than cigarette smoking being a possible method of self-medication, there appeared to be an elevated risk of smokers becoming schizophrenic. Their findings suggest that smoking cigarettes might be one of the causes.

For their evidence, the team of researchers analyzed 61 studies involving 15,000 smokers and 273,000 non-smokers that were conducted around the world. They discovered that, in comparison to the general population, schizophrenic patients looking for treatment were three times more likely to be smokers of cigarettes. Also, daily smokers developed the symptoms about a year earlier than other smokers. A fourth of the population of Western countries smoke cigarettes.

Co-author of the study, James MacCabe of King’s College, who is a doctor of psychiatric research, was not surprised by finding out that over half of schizophrenics smoke. He was taken by the data pointing to cigarette smoking not being a method of self-medication, as had previously been widely believed.

He explained his reasoning by saying that people who were just developing schizophrenia should not be any more likely to smoke cigarettes than the general populace. Instead, if the surmise was accurate, “the smoking would develop in response to the symptoms.”

The 61 studies that the research team analyzed did not point to that conclusion. Rather, based on the data the researchers examined, they noticed a link between people who began smoking cigarettes at a younger age than other smokers and an increased risk of developing schizophrenia. In other words, the people in the studies began smoking cigarettes long before any symptoms of schizophrenia emerged.

Though there have not been any findings yet to prove it, there is a suggestion that can be drawn that the nicotine in cigarettes causes the brain to produce and increased amount of the chemical dopamine. Dopamine has been discovered in the pleasure and rewards regions of human brains and the chemical helps control these responses in people.

As Sir Robin Murray, a professor of psychiatric research at King’s College London, put the possible relationship between nicotine exposure from cigarette smoking leading to an increase in dopamine levels in human brains and a higher risk of developing schizophrenia, “It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.”

An increase in the levels of dopamine in human brains has been linked to cases of psychosis and schizophrenia. Some of the medications that schizophrenics take are aimed at reducing the levels of dopamine activity in their brains.

In particular, in cases in which there is a family history of schizophrenia and/or drug and alcohol abuse, the study’s co-author, MacCabe, has suggested it would be a good idea for any smokers in the family to stop smoking cigarettes. Past studies have shown positive physical health benefits of quitting smoking, but now, the study by researchers at King’s college London suggests that kicking the habit might also be good for one’s mental health.

While there does seem to be a link between cigarette smoking at a young age leading to schizophrenia later in life, the authors of the study caution that longer-term studies clearly establishing this link need to be done. Also, most cigarette smokers do not become schizophrenic, indicating that other factors are involved.

But, there does seem to be a link between people who eventually develop psychosis and schizophrenia and the age at which they began smoking. Among the portion of the populace who are cigarette smokers and who develop schizophrenia, it is possible that nicotine or some other substance in cigarettes triggers the dopamine levels in their brains to be raised, either causing or worsening their symptoms.

MacCabe hopes that this preliminary study of 61 worldwide studies will lead to further efforts and studies that might establish an even clearer link between cigarette smoking and schizophrenia. In the general populace, roughly out of every 100 people could be classified as being schizophrenic. Among cigarette smokers, that increases slightly, to 2 out of every 100 people. No randomized clinical trial studies have yet been conducted. Whenever those are undertaken, if they also demonstrate a link, cigarette smokers might have one more good reason for giving up their habit.

Written and Edited By Douglas Cobb

Voice of America: Study Hints at Link Between Smoking,
Higher Schizophrenia Risk
Science World Report: Smoking And Mental Illness: Schizophrenia
Risk Increases With Cigarettes
BBC News: Smoking ‘may play schizophrenia role’
Photo Courtesy of Daniel Hoherd’s Flickr Page – Creative Commons 2.0

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