Tuesday, July 15, 2008

Persistence of anxious temperament - brain correlates

The temperament we display in early childhood (introvesion versus extroversion, high versus low reactivity, anxiety in unfamiliar versus familiar situations, etc) is largely genetically determined and persists through life. The work of Kagan and others has shown that children classed as highly reactive as babies are more likely to be subdued in unfamiliar situations and report a dour mood and anxiety over the future. Anxious temperament is an early predictor of the later risk to develop anxiety, depression and drug abuse related to self-medicating. It becomes increasingly clear that people with anxious temperaments are come wired that way, telling them to calm down just doesn't work. Kalin and his colleagues here at Wisconsin have produced an interesting study on the relevant brain correlates of this behavior by looking at brain activity, anxious behavior and stress hormones in adolescent rhesus monkeys, which have been used in numerous studies as models to understand anxious temperament in human children. They found that individuals with the most anxious temperaments showed higher activity in the amygdala, which regulates emotion and triggers reactions to anxiety, such as the fight or flight response. These anxious monkeys had more metabolic activity in the amygdala in both secure and threatening situations. These differences remained over several years of testing. From their abstract:
Regardless of context, results demonstrated a trait-like pattern of brain activity (amygdala, bed nucleus of stria terminalis, hippocampus, and periaqueductal gray) that is predictive of individual phenotypic differences. Importantly, individuals with extreme anxious temperament also displayed increased activity of this circuit when assessed in the security of their home environment. These findings suggest that increased activity of this circuit early in life mediates the childhood temperamental risk to develop anxiety and depression. In addition, the findings provide an explanation for why individuals with anxious temperament have difficulty relaxing in environments that others perceive as non-stressful.

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