Stress and the brain

Several studies have shown that chronic exposure to stress can lead to various structural changes in the brain, with long-term effects on the nervous system. Among these changes, some are frequently cited :

• Atrophy of the brain mass and decreased weight

• Atrophy and impaired neurogenesis (formation of new neurons) in the hippocampus and prefrontal cortex, regions involved in decision, learning, memory and attention

• Hypertrophy of the amygdala, involved in the regulation of emotions, anxiety and aggression

These structural changes are known to lead to functional impairments. For example, decreased hippocampal volume is linked with memory disorders, such as impaired spatial memory and disturbed conversion of short-term memory to long-term memory. Similarly, an hyperactivated amygdala can trigger an exaggerated fear response and lead to anxiety. Of course, the adverse effects of stress depend on the type, timing, duration and intensity. Mild stress has been shown to improve cognitive function, and if the stress occurs around the time of learning, it positively affects the encoding of the information in the memory. But if it goes beyond an (individual) pre-determined threshold, it has consequences on the hippocampus and prefrontal cortex structures and can cause cognitive disorders.

Continuous release of stress mediators due to chronic stress has several other effects on brain function. It dysregulates the sleep system, activating arousal and suppressing sleep, which leads to insomnia, loss of sleep and excessive day somnolence. It also weakens the reward system, causing depression as well as eating disorders and increased propensity to abuse alcohol or drugs. Moreover, chronic stress at work can lead to decreased self-esteem and irritability, which in turn triggers inappropriate behavior and burnout.

Prolonged activation of the stress system usually initiates a vicious cycle, in which behavioral dysfunctions lead to psychosocial problems in family, peer groups, school and/or work, which cause further changes and exacerbate these maladjustments.