Kids and teens are especially vulnerable.
Since 1998, scientists in the Netherlands have been watching 129 people grow up. Over those 20 years, they observed and obsessively measured their patients’ brain matter. Now, the results are in: What they found suggests that childhood stress may accelerate brain maturation, but that’s not necessarily a good thing.
This research, published Friday in Scientific Reports, showed that the brains of people who had experienced stress in early life — like divorce or illness — were more likely to mature faster. To measure brain maturation, they tracked reductions in the volume of gray matter (GMV) — a cellularly dense tissue scattered throughout the brain. While it may sound counterintuitive that a brain gets smaller as it matures, reduction is normal during adolescence, lead researcher Anna Tyborowska, P.h.D student and researcher at , the Behavioral Science Institute (BSI) at Radboud University, tells Inverse. The general idea is that brains are born bigger than they need to be, but as life experiences highlight the most essential parts, the less crucial bits get “pruned” away.
But there is one important catch: There is such a thing as maturing too soon.
“GMV increases during childhood and then starts to decline across adolescence,” Tyborowska tells Inverse. “Structures like the prefrontal cortex and amygdala, which are important for social-emotional processes, also mature during this time. These same structures are also rich in glucocorticoid receptors (stress hormones), which are activated by stress. Therefore, they are particularly susceptible to the effects of stress.”
Early Childhood Stress
The team looked at the link between brain matter and stress during two periods of their participants’ lives: early childhood (age 1 to 5) and adolescence (14-17 years). In participants that had experienced two or more early childhood stress events, Tyboroska and her team found that GMV decreased in the prefrontal cortex more than those who didn’t. She hypothesized that this was due to premature brain maturation: Instead of waiting until adolescence to decline, the GMV in the stressed-out cohort decline early. The effects of this, she says, are felt most in brain plasticity — the brain’s ability to adapt to changing stimuli.
There may an evolutionary reason for pruning in response to early stress, the researchers hypothesize. Early life stress might prematurely set the process of brain maturation into motion to help ensure survival. But while a rapidly matured brain might have kept humans alive in leaner times, it may also have hampered brain plasticity — the brain’s ability to adapt.
“It is an adaptive mechanism at a time of heightened stress,” Tyborowska adds. “However, it can also prevent the brain from adjusting to the current environment given the developmental plasticity and flexibility that is typically afforded during adolescence. This in turn can lead to later costs for mental and physical health.”
Stress During Adolescence
People who experienced stress during adolescence — say, having low self-esteem in junior high or high school — had different changes in their grey matter. In participants who experienced stress during this period, GMV was shown to increase in some portions of the brain, like the right anterior cingulate cortex — an area that links the emotional limbic system and the “cognitive” thought mechanisms of the prefrontal cortex. Those who displayed these neurological changes were those who displayed “un-emotional and callous traits” or who “were disliked by their peers,” suggesting that stress during adolescence can shift brain development in ways that affects teens’ mental health.
Tyborowska is adamant that changes in the brain are not uni-directional, which is why she will continue to measure GMV in her 129 subjects. “It is important to examine trajectories of grey matter development and not only static differences,” she says, noting that these findings are the first of many more to come.