Adolescents treated with the antidepressant fluoxetine — better known by its commercial name, Prozac — appear to undergo changes in brain signaling that result in changed behavior well into adulthood, says a new study.
Adult mice and rats who were administered Prozac for a stretch of mid-adolescence responded to daunting social and physical challenges with less despair than animals who passed their teen years unmedicated, a team of researchers found. But, even as adults long separated from their antidepressant days, the Prozac veterans reacted to stressful situations with greater anxiety than did the adult Prozac virgins.
The latest research, published this week in the Journal of Neuroscience, offers evidence that treatment with a selective serotonin reuptake inhibitor — an SSRI antidepressant — has long-lived effects on the developing brain. It also zeroes in on how and where fluoxetine effects those lasting changes: by modifying the cascade of chemical signals issued by the brain’s ventral tegmentum — a region active in mood regulation — in stressful situations.
Yet, the new research raises more questions than it answers, since the changes in adults who were treated with Prozac as adolescents seem contradictory. Sensitivity to stress appears to predispose one to developing depression. So how does a medication that treats depression in children and teens — and that continues to protect them from depression as adults — also heighten their sensitivity to stress?
“These findings underscore the complexity of drug and intracellular manipulations in the immature brain,” the authors write. Perhaps, anxiety and depression — often treated as if they were indistinguishable — have a far more complicated relationship to one another than has been appreciated. Perhaps, they suggest, the chemical signaling changes brought about by Prozac treatment have surprising and contradictory effects somewhere else in the brain. Or perhaps the adolescent brain and the adult brain respond differently to stress, so that a Prozac effect unseen in adolescence will become evident in adulthood.