Study finds enzyme linked to depression in ex-smokers

August 3, 2011 2:47:57 PM PDT
There may be a medical reason why some heavy smokers become depressed once they kick the habit.

Canadian researchers scanned the brains of nonsmokers, moderate smokers and heavy smokers. They found that after a person quit smoking he or she experienced an increase in an enzyme that regulates mood.

Earlier research has linked that enzyme to increased depression. This applies to heavy smokers, meaning people who smoke 25 or more cigarettes a day.

The study appears in the august issue of the journal "Archives of General Psychiatry."