A new study published this week in the journal Scientific Reports looked at the effects of stress on the development of the brain, and particularly on how fast the brain matures during two crucial stages in life, early childhood and adolescence.
Conducted by scientists from Radboud University in the Netherlands, the research — spanning two decades — aimed to uncover how stress in different stages of life shapes the adolescent brain and influences the connections between brain cells.
As Radboud University explains, during adolescence, the brain goes through a natural process of pruning, in which all the previously made neural networks — entire circuits of neurons connected through synapses that tell them to carry out specific functions — are refined and upgraded to better, more efficient versions.
According to the new findings, stress experienced early in life leads to more pruning in the adolescent brain, as well as a faster development, or maturation, of certain cerebral regions involved in perceiving emotions and moderating social behavior.
Started back in 1998, the long-term research followed a group of 37 subjects for the course of 20 years and analyzed the impact of two types of stress factors experienced during early childhood (0-5 years) and adolescence (14-17 years).
The study initially enrolled 129 one-year-old children and their parents and began by monitoring how these children interacted with their family, friends, and classmates. The team paid close attention to the children’s play sessions, while also analyzing their brain activity with MRI scans.
The two main stress factors that were kept under observation in terms of their effects on the brain had to do with negative life experiences, such as illness or parents getting divorced, and negative influences from the social environment, such as low peer esteem at school.
The researchers were particularly interested in finding out how these stressful experiences impact the maturation of three key brain regions — the prefrontal cortex, the amygdala, and the hippocampus — which are known to be stress-sensitive and which influence personality traits, how we behave around others, and how we deal with our emotions.
The findings revealed that early-life stress makes some of these brain regions mature faster. For instance, under the effects of childhood stress, the prefrontal cortex and amygdala reach a faster maturation during adolescence.
At the same time, stress experienced in the teen years makes the adolescent brain mature slower, something observed especially in the hippocampus and a different part of the prefrontal cortex.
While the researchers can’t say for sure if these changes are 100 percent attributed to stress, previous animal studies have suggested a causal link, says study lead author Anna Tyborowska, a Ph.D. student at the university.
“The fact that early childhood stress accelerates the maturation process during adolescence is consistent with theories of evolutionary biology,” she points out.
Nevertheless, a faster brain maturation could inhibit the brain’s flexibility to adapt to a new emotional environment after it has been hard-wired in a certain way, notes Tyborowska.
“From an evolutionary perspective, it is useful to mature faster if you grow up in a stressful environment. However, it also prevents the brain from adjusting to the current environment in a flexible way. In other words, the brain become ‘mature’ too soon.”
The researcher also reveals that “a stronger effect of stress on the brain also increases the risk of developing antisocial personality traits.”
The study is ongoing, as Tyborowska is currently conducting the eleventh round of measurements on the research participants, now in their twenties.
“Now that we know that stress affects the maturation of brain regions that also play a role in the control of emotions, we can investigate how this development continues later in life,” she says.