Brain Scans Find Clues to Depression in Heavy Smokers Who Quit

Brain scans have detected brain chemistry changes associated with depression in heavy smokers in early withdrawal. The results of the research, carried out at the Centre for Addictions and Mental Health in Toronto, appear in the August issue of Archives of General Psychiatry.

The study focused on the enzyme monoamine oxidase A (MAO-A), which metabolizes mood-enhancing chemicals and has been shown to be affected by cigarette smoke. In areas of the brain that modulate mood, such as the prefrontal cortex and the anterior cingulated cortex, elevations in MAO-A binding are connected with depressive episodes.

The study involved 24 healthy nonsmokers and 24 otherwise healthy smokers—12 of whom were moderate smokers (15-24 cigarettes per day) and 12 of whom were heavy smokers (25 or more cigarettes per day). Nonsmokers were subjected to a single positron emission tomography (PET) scan and smokers to two PET scans (one right after smoking and one in early withdrawal).

The results found that shortly after stopping smoking, the heavy smokers (but not the moderate smokers) had a significantly elevated MAO-A density—23.7% in prefrontal cortex and 33.3% in the anterior cingulated cortex. Heavy smokers also reported a more depressed mood during withdrawal compared with when they were smoking.

“Understanding the neurobiology of heavy cigarette smoking is important because those who smoke heavily are much more likely to have major depressive disorder and to experience medical complications resulting from cigarette smoking,” the study authors write. They also suggest that tests should be set up to gauge the effectiveness of MAO-A inhibiting drugs in helping heavy smokers avoid depression while quitting.

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Withdrawal from Heavy Cigarette Smoking Associated With Brain Imaging Changes in Regions Related to Mood Regulation (abstract) [Archives of General Psychiatry]