January 6, 2009

Teens' Brains on Fear

Researchers were surprised to find that teens' brains don't respond to a fear the same way adults' do.

A new study published in the journal Biological Psychology reports that though teens and adults react to frightening faces in the same way, what's going on in their brains may be quite different.

The results are surprising because they suggest that predicting adult behavior from teen behavior may not be as clear−cut as was previously thought.

In the healthy teens, the researchers found what they expected ... [h]owever, in the anxious and depressed teens, the results were reversed...

The neurotransmitter serotonin is important in regulating the fear response; after serotonin is released from a nerve cell, it is taken back into that cell for future use, with the help of a protein called the serotonin transporter. Changes in the gene that codes for the serotonin transporter may lead to less serotonin being recycled and are associated with anxiety and depression in both teens and adults.

People inherit one copy of the transporter gene from each parent, and these copies may be either short or long versions of the gene. Earlier studies have shown that adults with at least one copy of the short variety of the gene often suffer from anxiety and depression, and also react differently when they are presented with images of frightening faces.

To test whether the same was true for teens, Jennifer Y. F. Lau and her team used functional MRI imaging to compare the brains of 33 normal and 31 depressed or anxious teens while they were viewing pictures of scary faces.

In the healthy teens, the researchers found what they expected: the brains of those with at least one short copy of the serotonin transporter gene reacted more strongly than those with two copies of the long version. However, in the anxious and depressed teens, the results were reversed: the brains of those who had at least one copy of the short gene reacted less than those with two copies of the long gene.

Clearly the results were not what the researchers would have expected, as typically the adolescent brain and behavior are good predictors of the adult brain and behavior. Lau and her colleagues say that more research will be needed in the future to determine exactly why this is the case, but it may be partially explained by the fact that teens and adults react differently in the face of a perceived threat.

The research was conducted by researchers at the National Institute for Mental Health.

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