Approximately 50 percent of teens treated for depression will relapse within a five year period, according to a new study conducted by Duke University.

A research team from Duke’s Department of Behavioral Sciences conducted a study of 86 boys and 110 girls with a mean age of 14 who had taken part in a previous trial which had been divided into four groups: Prozac (fluoxetine) alone, CBT alone, fluoxetine and therapy, or placebo.

The researchers found that regardless of which treatment group they were placed in, about 47 percent of the teens relapsed at some point. And girls were more likely to experience relapse than boys. About 58 percent of girls had a relapse event versus 33 percent of boys. Teens of both sexes with anxiety disorders were also more likely to have a relapse.

As for the greater preponderance of girls relapsing, the research team reasoned that anxiety may be the culprit, since anxiety disorders also predicted a return to depression. There is a general clinical consensus that girls experience more anxiety disorders than boys.

These results point to the need to gear research toward treatments that prevent future depressive recurrences.

The aforementioned team’s findings appear in the November 1, 2010 issue of Archives of General Psychiatry.