Teens’ responses to danger or fear remain strong even when the threatening situation has passed, according to a new study conducted by Weill Cornell Medical College experts.
The report, which was published in the Proceedings of the National Academy of Sciences (PNAS), claims that when a threat hits an adolescent’s brain, their capability to make the fear disappear is lost, which could account for the anxiety and stress normally present during teenage years.
This is the first study to decode fear acquisition and fear extinction learning at neuron level in mice – mice synpaptic activity in this area is very similar to what occurs in human neuronal networks.
Dr. Siobhan S. Pattwell, commented:
“This is the first study to show, in an experiment, that adolescent humans have diminished fear extinction learning. 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.”
According to Dr. Francis Lee, a professor of pharmacology and psychiatry at Weill Cornell Medical College and an attending psychiatrist at NewYork-Presbyterian Hospital/Weill Cornell Medical, results from the trial reveal that during adolescence, changed plasticity is present in the prefrontal cortex of the the brain, as well as lack of ability to let go of fear.
“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 ares function well in both younger and older mice, neurons involved in fear extinction are not as active in adolescent mice. 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 desensitization 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 efficient during this sensitive developmental period in adolescents,” said Dr. Lee.
Fear learning is an extremely adaptive process we have acquired during the evolutionary process to respond properly to danger triggers. When it comes to psychiatric disorders, fear is more persistent, and tends to linger around even after the dangerous or fearful situation is gone. This type of fear is a main part of post-traumatic stress disorder (PTSD), as well as many other anxiety disorders.
Current therapies, including exposure therapy, work by making a person vulnerable to certain cues which may be linked to something they are fearful of. These kinds of treatments are used for many different types of fear, including teen anxiety about going to school and post-war PTSD.
Children and teens are being diagnosed with anxiety disorders more and more, however, fear extinction exposure method success rates are unknown. The researchers of this study set out to determine if these methods actually help the adolescents.
The trial took place at the Sackler Institute for Developmental Psychobiology at Weill Cornell and was conducted by its director, Dr. B.J. Casey, a professor of psychology in psychiatry at Weill Cornell.
During the investigation, participants – including adults, adolescents, and children – were asked to wear earphones and meters to measure their sweat, while they looked at computer monitors that showed a series of yellow and blue squares. One square was matched with a distressing noise. In other words, half the time the blue square would make a sound that the people did not like.
When increased sweat was present, this meant that the volunteers developed a fear of the sound, and were associating the image with the noise.
A day later, the group returned to the facility, and were asked to look at the same series as the day before. However, the square did not produce the unpleasant noise that it had the previous day.
Dr. Pattwell explained, “But teenagers didn’t decrease their fear response, and maintained their fear throughout subsequent trials when no noise was played.”
Researchers note that the children and adults involved in the trial easily learned that neither the blue or yellow squares were associated with a sound, and therefore, their fear was quickly decreased.
The investigation involving mice, which involved normal fear conditions found often in animal studies of this kind, found the results to be very similar. Twenty-nine day old mice, which is considered adolescence, did not have a decrease in their fear responses, even after the trigger was not present. In addition, their fear responses did not decrease at all even when they were older.
Dr. Ipe Ninan, an electrophysiologist at NYU Langone Medical Center and an assistant professor of psychiatry, worked with the experts to analyze the mice brains during the trial.
They determined that the prelimbic region in the prefrontal cortex, which is the area of the brain that deals with emotion, is triggered during fear acquisition. The Infralimbic prefrontal cortex works by eliminating this fear association.
Pattwell continued, “In young and old mice, we see plasticity, which is activity in the infralimbic cortex, which helps the animals decrease their fear response when a threat no longer applies. Interestingly, we didn’t witness similar activity in adolescent mice.”
Authors note that much more research should take place in order to completely understand fear response and its role in humans during their teenage years. This includes whether genes play a role in how susceptible a teen is to fear learning, and what can and should be done to help these adolescents tackle their fears.
Dr. Lee concluded:
“We need to investigate personalized approaches to treatment of these fear and anxiety disorders in teens. 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.”
Written by Christine Kearney