New evidence suggests that popular selective serotonin reuptake inhibitor (SSRI) antidepressant medications can substantially change patients' personalities, and researchers speculate that it is these changes in personality - rather than the supposed alleviation of depressive symptoms - that are responsible for improvements in mood. The research, conducted by psychologists from the University of Pennsylvania, Northwestern University and Vanderbilt University, counters the common assumption that personality changes during SSRI treatment occur only as a byproduct of alleviating depressive symptoms. The researchers note that the advantage of paroxetine (a popular SSRI antidepressant) over placebo in changing personality appears far more drastic than its advantage over placebo in alleviating depression.
"Investigating how SSRIs affect personality characteristics like neuroticism and extraversion may thus lead toward a more refined understanding of the mechanisms of SSRIs," said Penn researcher Robert DeRubeis. "SSRIs perhaps can be viewed as personality-normalizing agents, potentially useful in treating many disorders associated with high neuroticism and low extraversion."
Among responders to paroxetine, those for whom neuroticism changed the most during treatment were also those least likely to relapse. It would appear that change in neuroticism - or in a phenomenon related to self-reported neuroticism - served to reduce vulnerability to relapse.
In the study, published in the Archives of General Psychiatry, researchers randomly assigned 240 participants with major depressive disorder, or MMD, to take a placebo for eight weeks, paroxetine for 16 weeks or receive cognitive therapy for 16 weeks. Their personalities and depressive symptoms were assessed before, during and after treatment. After treatment with paroxetine or with cognitive therapy, responders were followed for a year to assess depression relapse.
As in similar previous trials, patients taking paroxetine experienced moderately greater depression improvement than those receiving placebo. In contrast, changes in neuroticism and in extraversion were far greater for patients taking paroxetine, relative to those receiving placebo, with cognitive therapy in between. Patients taking paroxetine reported 6.8 times as much change on neuroticism and 3.5 times as much change on extraversion as placebo patients.
"Our findings lead us to propose a new model of antidepressant mechanism," said lead author Tony Z. Tang of Northwestern University. "Our data suggests that modern antidepressants work partly by correcting key personality risk factors of depression."
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Source: University of Pennsylvania
