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　　Studies have linked cigarette smoking to a number of health problems, including lung cancer and heart disease. Now, a new study shows a possible link between smoking and the disabling brain disorder schizophrenia. People with schizophrenia hear and see things that are not real. Patients also may believe that others want to harm them.

　　Cigarette smoking is very common among people with mental disorders, especially those with schizophrenia.

　　Sameer Jauhar noted the connection.

　　A man flicks ashes from his cigarette over a dustbin in Shanghai January 10, 2014. (REUTERS/Aly Song)
　　A man flicks ashes from his cigarette over a dustbin in Shanghai January 10, 2014. (REUTERS/Aly Song)
　　"As a psychiatrist it's always something you think about, because you always see patients with psychotic illnesses smoking. People generally put it down to self-medication."

　　Sameer Jauhar is a psychiatric researcher at King's College London. He spoke recently during a podcast to the online journal, The Lancet Psychiatry. The journal published his study, which noted the relationship between cigarette smoking and schizophrenia.

　　Dr. Jauhar and a King's College team found that smoking may in some way increase the risk of developing schizophrenia. They examined 61 studies from researchers around the world. They found that smoking is three times more common among schizophrenic patients coming to treatment for the first time compared to the general population.

　　James MacCabe was one of the writers of a report on the study. He is a doctor of psychiatric research at King's College. He says he was not surprised to find that more than half of people with schizophrenia smoke. He says the finding raises questions about the belief that people who have mental disorders smoke to ease their symptoms.

　　"If the explanation was self-medication, you would expect that when people started to develop schizophrenia they would be no more likely to smoke than anybody else, and the smoking would then develop in response to the symptoms."

　　The study found that those who developed schizophrenia began smoking at a younger age than other smokers, before their mental problems appeared.

　　There is also a suggestion about the drug nicotine, but not the findings to support it. Nicotine is found in tobacco products. The researchers suspect nicotine may help fuel production of the brain chemical dopamine. This chemical affects the parts of the brain that control how a person reacts to praise and pleasure. Increased levels of dopamine have been seen in people with mental illness. Medicines used to treat 　　schizophrenia work to reduce dopamine activity in a patient's brain.

　　James MacCabe says there is not enough evidence yet to confirm the link between cigarette smoking and the development of schizophrenia. But when the link is confirmed, he says, people who have a family history of the illness might be advised not to smoke.

　　"There are many reasons why we should try to reduce rates of smoking in the population for physical health reasons. But this suggests that possibly doing so would also actually benefit people's mental health."

　　The researchers are calling for more studies on the possible link between smoking and nicotine dependency in the development of psychotic disorders.

　　I'm Christopher Jones-Cruise.

　　VOA Health Correspondent Jessica Berman reported this story from Washington. Christopher Jones-Cruise adapted it for Learning English. George Grow was the editor.

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