All the newer antidepressant medications are about equally effective, but side effects can vary, a government report says.

The Agency for Healthcare Research and Quality (AHRQ) examined 2,100 studies published worldwide from 1980 to February 2006 on treatment of acute and chronic major depression and chronic dysthymia, a moderate form of depression. Synthesizing results from the best 293 trials, investigators concluded that the various selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors produce similar rates of effectiveness.

They also determined that:

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• 38% of patients do not respond within the first 6-12 weeks of treatment with any drug, and 54% experience only partial improvement.
• 61% experience side effects. The most common are nausea, vomiting, constipation, diarrhea, dizziness, headache, and sleeplessness, but each drug has its own set of effects, which can include weight gain and sexual dysfunction.
• 25%-33% will improve with the addition or substitution of a different drug.
• Paroxetine (Paxil) and venlafaxine (Effexor) have the highest discontinuation rates; fluoxetine (Prozac) has the lowest.

Direct evidence from head-to-head trials was sufficient to conduct meta-analyses for four drug-drug comparisons. In these, sertraline (Zoloft) was found superior to fluoxetine and escitalopram (Lexapro) was superior to citalopram (Celexa).

The full report and a nine-page executive summary are available from effective healthcare (Accessed February 7, 2007).