NEW YORK (Reuters Health) - Cigarette smoking may have effects on the human brain similar to those of antidepressant drugs, possibly explaining the high rate of smoking among depressed people and their resistance to quitting, a team of researchers reports

``Chronic smoking produces 'antidepressant-like' effects on the human brain,'' lead author Dr. Gregory A. Ordway, a professor of psychiatry at the University of Mississippi Medical Center in Jackson, told Reuters Health. ``This may contribute to the high incidence of smoking and difficulty to quit in those who are depressed.'' Researchers have noted previously that depressed people are more likely to smoke and are more resistant to quitting. However, it was unclear if nicotine or other chemicals taken in during smoking directly affected the brains of those who were depressed. Ordway, along with lead collaborator Dr. Violetta Klimek, examined a portion of the brain associated with depression known as the locus coeruleus. The researchers compared a portion of this brain tissue taken after death from seven people who had been heavy smokers and nine nonsmokers, all of whom had been mentally healthy. The investigators found that the brains of long-term smokers had neurochemical abnormalities similar to the brains of animals treated with antidepressant drugs, according to the report published in the September issue of the Archives of General Psychiatry. Specifically, Ordway said, the brains of long-time smokers had significantly fewer alpha-2 adrenoceptors and significantly less of the enzyme tyrosine hydroxylase, which helps to manufacture the brain chemicals noradrenaline and dopamine. These two effects have been reported in animals exposed to antidepressant drugs and are also two of the markers used to identify potential antidepressant medications, Ordway noted. ``This is the first time someone demonstrated that chronic smoking produced biological effects in the brain that (are associated with) antidepressive effects in the brain,'' he said. Ordway pointed out that it was still undetermined whether smoking actually caused this effect, or whether those with this brain chemistry were more susceptible to becoming smokers. However, he added, he suspected smoking was in fact causing these neurochemical changes and planned to conduct animal studies to find out. Ordway also emphasized that even if cigarette smoking did have some antidepressive effect, he still would not recommend its use, but hopes this research could aid in designing better smoking cessation treatments for depressed patients. ``Certainly, this is no reason to take up a smoking career,'' he said. ``There are so many bad things about smoking you can't justify the use of it.''

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