Turns out, the inability to block out fear during adolescence may be an innate trait.
In a new study, Weill Cornell Medical College researchers determined that once a teenager’s brain is triggered by a threat, the ability to suppress an emotional response to the threat is diminished.
This finding may explain the peak in anxiety and stress-related disorders during this developmental period.
The study, published in the online edition of the Proceedings of the National Academy of Sciences, is the first to decode fear acquisition and fear “extinction learning,” down to the synaptic level.
Researchers studied the brains of mice, which mirror human neuronal networks in addition to performing human experiments.
A key finding is that while acquired fear can be difficult to extinguish in some adolescents, 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,” said the study’s lead author, Dr. Siobhan S. Pattwell.
“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 percent 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, said the study’s senior co-investigator, Dr. Francis Lee.
“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,” said Lee.
“The new knowledge that a teenagers brain’s synaptic connections may not respond 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.”
Fear learning is a highly adaptive, evolutionarily conserved process that allows one to respond appropriately to cues associated with danger.
In the case of psychiatric disorders, however, fear may persist long after a threat has passed, and this unremitting and often debilitating form of fear is a core component of many anxiety disorders, including post-traumatic stress disorder (PTSD).
Existing treatments include exposure therapy — designed to expose an individual slowly to the cues associated with a perceived threat. This technique is used for a variety of fears, from wartime PTSD to fear of flying, as well as serious adolescent anxiety about school, said Lee.
Anxiety disorders are increasingly being diagnosed in children and adolescents, but the success rate of fear extinction-based exposure therapies are currently not known in this population. This study aimed to discover if they could be effective — and why or why not.
The human experiment asked a group of volunteers — children, adolescents and adults –to wear headphones and skin sweat meters while looking at a computer screen with a sequence of blue or yellow square images.
One of the squares was paired with a really unpleasant sound. For example, 50 percent of the time the blue square would set off the noise.
If the participants acquired a fear of the noise, they showed increased sweat when viewing the image that was paired with it, said Pattwell.
The same group was brought back the next day, and again viewed a sequence of blue or yellow squares, but this time there was no associated noise. “But teenagers didn’t decrease their fear response, and maintained their fear throughout subsequent trials when no noise was played,” she said.
However, the researchers documented that, unlike the teens participating in this study aged 12-17, both children and adults quickly learned that neither square was linked to a noxious sound, and this understanding rapidly decreased their fear response.
According to researchers there is much more to explore about the fear response and its decoding in human adolescents, such as whether genes contribute to susceptibility to altered fear learning, and most importantly, what can be done to help the adolescent population overcome fear.
“We need to investigate personalized approaches to treatment of these fear and anxiety disorders in teens,” said Lee.
“It is essential that we find a way to help teenagers become more resilient to the fear they experience during adolescence to prevent it from leading to a lifetime of anxiety and depression.”