A placebo-controlled research study has discovered that a commonly-prescribed depression treatment — paroxetine (Paxil) — appears to have a specific effect on one’s personality. The researchers found similar personality-changing effects of cognitive-behavioral therapy as well.
The researchers, led by Tony Tang from Northwestern University, sought to examine whether patients with clinical depression who were taking selective serotonin reuptake inhibitors (SSRIs) report greater changes in two important personality components — neuroticism and extraversion — than patients receiving a sugar pill (an inert placebo). They also studied whether cognitive behavioral therapy (CBT), a commonly prescribed psychotherapy treatment for depression, had a similar effect.
Neuroticism and extraversion are 2 of the 5 primary personality dimensions in the Five-Factor Model of Personality. Neuroticism refers to a tendency to experience negative emotions and emotional instability. Extraversion encompasses social extraversion, dominance, and a tendency to experience positive emotions.
Participants were 240 moderate to severely depressed adult outpatients who scored 20 or above on a common depression measure called the Hamilton Scale for Depression (HAM-D).
The researchers found no significant differences between the two active treatments, the SSRI paroxetine (Paxil) and CBT. But both paroxetine and the CBT treatment outperformed placebo in changing depression, neuroticism, and extraversion scores significantly.
“To the best of our knowledge, these are the first findings from a randomized placebo-controlled trial to suggest that an SSRI treatment of MDD produces greater changes in neuroticism and extraversion than an inert placebo,” concluded the researchers.
“In other words, paroxetine demonstrated a true drug effect on neuroticism and extraversion scores, reflecting pharmacological specificity.”
The researchers also noted that their study was the first clinical trial to show that CBT can produce significantly greater change in neuroticism and extraversion than placebo.
Although SSRIs like Paxil are the most widely used treatment for clinical depression, our understanding of their mechanisms remains limited. “Selective serotonin reuptake inhibitors are also effective in treating several anxiety disorders and eating disorders, and recent studies have suggested that high neuroticism and low extraversion may be general risk factors for these disorders as well,” noted the researchers.
The researchers suggest their data support the “cause-correction model” of how SSRIs work to treat depression.
“One possibility is that the biochemical properties of SSRIs directly produce real personality change,” note the researchers. “[…B]ecause neuroticism is an important risk factor that captures much of the genetic vulnerability for [depression], change in neuroticism (and in neurobiological factors underlying neuroticism) might have contributed to depression improvement. Indeed, our […] analyses suggest that personality change can explain the advantage of paroxetine over placebo in antidepressant efficacy, rather than vice versa.”
The study appears in the December issue of the Archives of General Psychiatry.
Source: Archives of General Psychiatry