The antidepressant paroxetine doesn't just make people happier, it alters their personality as well.
Tony Tang at Northwestern University in Evanston, Illinois, and his colleagues studied changes in neuroticism and extraversion — two personality traits linked to depression and the neurotransmitter serotonin — in 240 patients in a 16-week trial with a one-year follow-up. Half of the patients received paroxetine, one quarter a placebo and one quarter cognitive therapy.
Placebo patients improved their depression scores but reported little change in personality. By contrast, patients on paroxetine reported a decrease in neuroticism and an increase in extraversion, even after the results were normalized for differences in depression improvement. Those with the greatest declines in neuroticism also showed lower relapse rates.
Rather than being a mere by-product of improved mood, these personality changes may help explain why drugs such as paroxetine work against depression in the first place.