Tang and colleagues looked to see if the SSRI, Paxil (brand name Seroxat), had effects beyond just treating depression symptoms. In their study they noticed dramatic changes not only in depression but a significant drop in neuroticism and marked increases in extroversion.

"Patients taking Paroxetine reported 6.8 times as much change on neuroticism and 3.5 times as much change on extroversion as placebo patients matched for depression improvement," said Tang.

"Those are very dramatic, notable changes. At the beginning of the treatment, they were way out there. Their neuroticism was abnormally high. By the end of treatment, they moved back into the boundary of the normal range," he said.

Tang mentioned that all SSRI would possibly have a similar effect. If these studies can be duplicated, then it will change the way physicians treat depression.

Says Dr. Ian Cook of the David Geffen School of Medicine at the University of California Los Angeles, "The conventional wisdom has been for many years that the changes in personality that one sees during treatment tend to be thought of as a reflection of getting the depression under control," he said. He further stated that these observations may help better predict who is at risk for depression and which of these individuals may benefit most from treatment.

Archives of General Psychiatry 2009.