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Young Mice on Prozac Turn into Anxious Adults

By Edward R. Winstead

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Depression and Bipolar Disorder

Adult mice that received Prozac as babies were not interested in exploring new environments like this maze.
A new study in mice suggests that Prozac and other drugs that regulate serotonin in the brain may interfere with the normal development of the brain if given early in life.

While the research has no immediate implications for humans, it nonetheless raises questions about the use of these drugs among pregnant women and children.

If what’s true for mice is true for people, then exposing the developing brain to drugs that target serotonin, the chemical associated with mood disorders, could cause changes in the brain that may predispose a person to develop a mood disorder later in life.

“The brain seems to respond differently to a drug that blocks the serotonin system while it is still developing compared to when it is no longer developing,” says Mark Ansorge of Columbia University College of Physicians and Surgeons in New York, where the study was done.

The human brain, he adds, is still developing well into the teenage years and is never static.

Reporting their findings in Science, the researchers say that the use by pregnant mothers and young children of drugs known as SSRIs (which include Prozac, Zoloft and Celexa) “may pose unsuspected risks of emotional disorders later in life.” But future studies will have to explore whether the mouse research applies to humans.

“Prior to this finding I have counseled women and young children to exhaust all the non-pharmacologic possibilities, such as psychotherapy, before resorting to drug treatment, and my advice remains the same,” says Jay A. Gingrich of Columbia, who led the study.

In the study, mice were given Prozac for 17 days during the first weeks of life and then lived “normal” lives in the laboratory until three months of age, when they took a battery of tests to assess their levels of depression and anxiety.

As adults, the mice were less likely than other mice to explore unfamiliar environments and appeared to be more cautious, which the researchers interpret as signs that the animals are a bit anxious.

The study was not motivated by recent concerns about whether some antidepressants are a factor in suicides among teenagers, though the findings will no doubt add to the discussion.

The study’s bottom line may be that serotonin is important to the brain as it develops and that disruptions to the system early on may cause problems later.

According to the researchers, some people, because of their genes, have less serotonin than others and if this is the case during childhood, it may explain a person’s vulnerability to depression in adulthood.

Ansorge, M.S. et al. Early-Life Blockage of the 5-HT Transporter Alters Emotional Behavior in Adult Mice. Science 306, 879-881 (October 29, 2004).

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