Antidepressants can cause distinct personality changes in depressed patients that go beyond simply relieving the depression, a new study has found.
The study found that people who were unassertive, pessimistic, prone to worry and prefer to be by themselves saw those personality traits change after they were a class on antidepressants called SSRIs (selective serotonin reuptake inhibitors) for just 16 weeks.
The findings are striking, researchers said, because it's long been thought that personality traits such as neuroticism and introversion change slowly or not at all over a lifetime.
In the study, 120 patients with moderate to severe depression, took the anti-anxiety SSRI Paxil (paroxetine), while 60 underwent cognitive therapy but took no medication, and another 60 took placebos for eight weeks. In the crossover phase of the study, half of the participants on placebo were then given Paxil for another eight weeks.
There was then a 12-month phase when half of those in the Paxil group stayed on Paxil and half were taken off the drug and given placebo pills.
All patients showed less depression after eight weeks, no matter which group they were in, the researchers report in the December issue of Archives of General Psychiatry. But those given placebo pills reported their relief from depressive symptoms was briefer and more muted than those on Paxil or cognitive therapy.
Patients who received Paxil were more likely to report reduced depression symptoms than patients in the other two groups. But, strikingly, they also reported reduced neuroticism and increased extraversion.
Neuroticism is characterized by anxiety, hostility, self-consciousness, impulsivity, and sensitivity to stress. Extraversion refers to being inclined to have positive emotions, assertiveness, and sociability.
SSRI medications relieve depression by altering brain chemicals in the brain's serotonin system. Since neuroticism and extraversion are also related to the serotonin system, it appears the medication also affect these personality traits.
"One possibility is that the biochemical properties of SSRIs directly produce real personality change," the researchers write.
"Furthermore, because neuroticism is an important risk factor that captures much of the genetic vulnerability for major depressive disorder, change in neuroticism and in neurobiological factors underlying neuroticism might have contributed to depression improvement."
It is unclear how long-lasting the changes in personality are, said the authors, who were led by Northwestern University psychologist Tony Z. Tang.
But the study found that patients whose personalities shifted the most were less likely to relapse into depression. And they said that monitoring those altered traits could be a useful, early gauge of whether a medication is working and how probable a recurrence would be.
The study was not funded by the makers of Paxil, but instead by the U.S. National Institute of Mental Health.
Tang said his study suggests doctors can focus on helping patients achieve fundamental personality changes, not just recover from an episode of depression.
But in an interview with the L.A. Times, Peter D. Kramer, the psychiatrist and author of the book "Listening to Prozac," said he worried the study raised ethical questions about "cosmetic psychiatry," in which healthy, non-depressed people might be encouraged to seek a brighter, more appealing personality through medication.
