The new study also confirms the existence of a "communication gap" between patients and physicians when it comes to the sexual impact of antidepressant therapy.

A major study of sexual dysfunction in people taking one of several "new generation" antidepressants shows that Wellbutrin (bupropion) and Serzone (nefazodone) are significantly less likely to cause sexual side effects than selective serotonin reuptake inhibitors (SSRIs) or serotonin/norepinephrine reuptake inhibitors (SNRIs).

"The SSRIs are known to cause sexual dysfunction as a side effect," notes lead investigator Anita Clayton, MD, of the University of Virginia at Charlottesville "But until now, there hasn't been a study to look at all the new generation antidepressants to see how they compare."

Clayton profiled the new study and presented preliminary findings at this year's annual meeting of the American Psychiatric Association. The study surveyed 6,297 patients who volunteered to provide information about their sexual health under antidepressant therapy. The doctors involved in the study were primary care physicians, not specialists in the treatment of psychiatric problems.

Eight antidepressants were evaluated: four SSRIs [Celexa (citalopram), Paxil (paroxetine), Prozac (fluoxetine), and Zoloft (sertaline)]; two SNRIs [Effexor (venlafaxine) and Remeron (mirtazepine)]; Wellbutrin (bupropion); and Serzone (nefazodone). The study was sponsored by GlaxoSmithKline, the maker of Wellbutrin.

The bottom line

The rate of sexual dysfunction for all the antidepressants combined was 37%. Individually, Wellbutrin had the lowest rate with 22% (25% for the sustained-release formulation). The average rate for SSRIs and SNRIs combined was approximately 40%. In patients with no probable cause of sexual problems other than their antidepressant medication, Wellbutrin was associated with sexual dysfunction in just 7%, compared with rates of 23% to 30% among patients taking Celexa, Prozac, or Effexor. (Note: These are preliminary results; a complete description of the study and its findings has yet to be published.)

Don't ask, don't tell?

Somewhat surprising in this study was the discrepancy between the rate of sexual dysfunction found (37%) and the rate predicted by physicians (20%)--surprising, because the published rates of sexual dysfunction with SSRIs are generally much higher, exceeding 50%, for example, in one study with 324 patients who had normal sexual function prior to starting SSRI therapy and no other identifiable cause of their sexual problems.

The explanation centers on a communications barrier. "Physicians and patients are generally reluctant to talk about sexual problems," Clayton notes. "Therefore, physicians often underestimate the prevalence of antidepressant-associated sexual dysfunction and the impact on patients. ... [T]his study demonstrates that physicians would get a more accurate assessment of sexual problems by directly asking patients, rather than relying on voluntary reports."

Nearly half the patients in this study reported that their doctor had not discussed sexual functioning with them prior to initiating antidepressant therapy. This mirrors research by the National Depressive and Manic-Depressive Association (NDMDA), which found that 69% of doctors said they usually mention sexual problems as a possible side effect of antidepressant therapy, but only 16% of patients could recall such a conversation. Equally important, only 36% of patients reported that their doctor had asked about their preferences or willingness to tolerate sexual side effects before deciding which antidepressant to prescribe.

--SexHealth.com