According to background information in a recent JAMA article (Arch Gen Psychiatry, 2009;66:1322-1330), two personality traits, neuroticism and extraversion, have been related to depression risk. Both traits have been linked to the brain’s serotonin system. It is that serotonin system which is also targeted by the class of antidepressants known as selective serotonin reuptake inhibitors (SSRIs).
Tony Z. Tang, Ph.D., of Northwestern University (Evanston, Ill.) and colleagues studied the effects of one particular SSRI, paroxetine, in a placebo-controlled trial involving 240 adults with major depressive disorder. A total of 120 participants were randomly assigned to take paroxetine, 60 to undergo cognitive therapy and 60 to take placebo for 12 months. Their personalities and depressive symptoms were assessed before, during and after treatment.
All participants experienced some improvement in their symptoms of depression, as one would suspect after taking a pharmaceutical antidepressant. However, even after controlling for these improvements, individuals taking paroxetine experienced a significantly greater decrease in neuroticism and increase in extraversion than those receiving cognitive therapy or placebo. “Patients taking paroxetine reported 6.8 times as much change on neuroticism and 3.5 times as much change on extraversion as placebo patients matched for depression improvement,” the authors write.
“One possibility is that the biochemical properties of SSRIs directly produce real personality change,” they write.
SSRIs are widely used to treat depression. It has not been made clear to many patients by their doctors, however, that the drugs may indeed induce a distinct change in personality, something the patient may not have bargained for.