Teens are more susceptible to continuous feelings of stress due to a difference in the way their brains process fear. Adolescents rely on earlier-maturing brain regions that aren’t as proficient as their adult counterparts in differentiating between danger and safety.
Jennifer Lau, Ph.D., of Oxford University and a research team compared the brain activity of healthy young people with healthy adults during a threat stimulus study.
For the test, volunteers were asked to view a series of photographs, including the following: a person with a neutral expression at first, then a fearful expression coupled with a loud scream; in some later photos, the same person with a neutral expression only (threat stimulus); a different person with a neutral expression only (safety stimulus).
Participants immediately rated how scared they felt after each photo. Both teens and adults reported feeling more afraid of the threat stimulus than the safety stimulus. However, compared to adults, the youth were less able to differentiate between the threat and the safety stimuli.
Through the use of functional magnetic resonance imaging, the research team discovered that teens had more activity in the hippocampus (which helps create and store new memories) and also in the right side of the amygdala (responsible for the fight-or-flight response) than adults while they viewed the threat stimulus compared with the safety stimulus.
Significantly, adults had more activity in a different brain structure—the late-maturing dorsolateral prefrontal cortex (DLPFC)—which is strongly involved in categorizing objects into different groups. In adults, activity in this region increased as they rated more fear in relation to the safety stimulus. The researchers suggest that the adults’ brains relied more on the DLPFC while trying to decide whether a stimulus was safe or not; this uncertainty was reflected in their fear ratings.
The study suggests that, when afraid, younger brains will rely mainly on the hippocampus and right amygdala, two earlier-maturing brain structures responsible for basic fear responses. On the other hand, adults rely more on the later-maturing prefrontal regions, an area associated with making more reasoned judgments and differentiating between real and false threats.
This variation may help explain why teens tend to express more pervasive worries and appear more vulnerable to stress-related problems, the researchers said. To better understand how fear responses mature over time, however, future research should include large, longer-term studies of similarly aged teens and follow them into adulthood.
The study is published online in the Proceedings of the National Academy of Sciences.