Think of the last time you were seriously frightened. Perhaps a car narrowly missed hitting you, or a loud barking dog suddenly lunged at a fence as you walked by. It can be hard to calm down after facing a threat. It turns out that this is especially the case for teenagers.
One reason for this is that teenagers seem to have a harder time realizing when a threat has passed than other age groups do. Once a teenager's brain registers a threat and is activated, their ability to suppress an emotional response to the threat is reduced. It is harder for them to calm down. This may explain why anxiety and stress disorders often show up during adolescence.
The researchers saw this effect in studies on both humans and mice. The human study had children, teenagers (ages 12-17) and adults view a sequence of images on a computer screen: blue squares or yellow squares. One of the colors was paired with a really horrible noise, and squares of that color would occasionally set off the noise when they appeared on the screen; squares of the other color never set off the noise.
Once a teenager's brain registers a threat and is activated, their ability to suppress an emotional response to the threat is reduced. This may explain why anxiety and stress disorders often show up during adolescence.
The next day, participants were brought back and the procedure repeated, except that no noise ever accompanied any of the computer images. Children and adults quickly learned that neither colored square was associated with a noise and there was no longer anything to fear, as seen in their sweat measurements. But the teenagers did not, continuing to respond as if the threat still existed.
Similar results were seen in threats to mice: adolescent mice did not decrease their fear response to stimuli that no longer existed, while younger and older mice did. In fact the adolescent mice never lost their fear response, even when they grew older.
Examination of the brains of these mice indicated that neurons in an area of the brain called the infralimbic prefrontal cortex become more active during fear extinction, the process of "unlearning" a fear. This activation was not seen in the adolescent mice in the study, a condition the researchers describe as a lack of synaptic plasticity.
Anxiety disorders seem to spike during or just before adolescence. A common treatment for fear is exposure therapy, where people are gradually exposed to whatever is causing their fear. For someone afraid of dogs, this might include spending time with a small, friendly dog. Studies suggest that exposure therapy only works on about 60% of the people it is tried on and there's very little information on how this breaks down for different age groups. The study suggests that it likely won't work as well in teenagers and that treating teenage fear will prove more difficult than treating fear in other age groups.
An article on the study, by researchers at Weill Cornell Medical College was published online by Proceedings of the National Academy of Sciences (PNAS) and will also appear in a future print edition of the journal.