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A new study by Weill Cornell Medical College researchers shows that adolescents' reactions to threat remain high even when the danger is no longer present. According to researchers, once a teenager's brain is triggered by a threat, the ability to suppress an emotional response to the threat is diminished which may explain the peak in anxiety and stress-related disorders during this developmental period.
The study, in the early online edition of the Proceedings of the National Academy of Sciences (PNAS), is the first to decode fear acquisition and fear "extinction learning," down to the synaptic level in the brains of mice, which mirror human neuronal networks.
Also, through human and rodent experiments, the study finds that acquired fear can be difficult to extinguish in some adolescents. By contrast, the study shows that adults and children do not have the same trouble learning when a threat is no longer present.
"This is the first study to show, in an experiment, that adolescent humans have diminished fear extinction learning," says the study's lead author, Dr Siobhan S. Pattwell, a postdoctoral fellow at the Sackler Institute for Developmental Psychobiology at Weill Cornell.
The findings in the study
"Our findings are important because they might explain why epidemiologists have found that anxiety disorders seem to spike during adolescence or just before adolescence. It is estimated that over 75% of adults with fear-related disorders can trace the roots of their anxiety to earlier ages."
The study findings suggest there is altered plasticity in the prefrontal cortex of the brain during adolescence, with its inability to overcome fear, says the study's senior co-investigator, Dr Francis Lee, professor of pharmacology and psychiatry at Weill Cornell Medical College, and an attending psychiatrist at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.
"This study is the first to show activity, at the synaptic level, for both fear acquisition and fear extinction - and we find that while these areas function well in both younger and older mice, neurons involved in fear extinction are not as active in adolescent mice," says Dr Lee. "If adolescents have a more difficult time learning that something that once frightened them is no longer a danger, then it is clear that the standard desensitisation techniques from fear may not work on them.
This new knowledge about the teenage brain's synaptic connections not responding optimally will help clinicians understand that the brain region used in fear extinction may not be as efficient during this sensitive developmental period in adolescents."
(EurekAlert, September 2012)
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