In addition to peer problems, societal factors that can contribute to anxiety and depression in children and teens include one that has always, really, been undeniable: socioeconomic disadvantage. Long-term studies have found that early poverty predicts later higher risk for internalizing problems, and functional MRI studies of children exposed to early life stress have shown increased amygdala reactivity to negative emotional stimuli.
In the Pediatric Imaging, Neurocognition, and Genetics study of 1,196 participants aged 3 to 21, lower family income and parental educations were significantly associated with smaller amygdala volume in adolescence. Lower parental education was significantly associated with higher levels of anxiety and depression (even after accounting for family history), and smaller amygdala volume was significantly associated with higher levels of depression, even after accounting for parental education and family history.
Teens process information with the amygdala, which plays a central role in threat detection and fear learning. Researchers have theorized that poverty-related stressors have an impact on the hypothalamic-pituitary-adrenal axis stress response and may literally revise how brain structures develop. Neuroimaging studies have shown links between socioeconomic factors and amygdala volume—children and teens with anxiety disorders or major depressive disorder tend to have different amygdala structure compared with typically developing children—but the “directionality of the associations” has been inconsistent. Moreover, some research in adults has found that initial episodes of major depression may increase amygdala volume and reactivity but after repeated depressive episodes, the amygdala volume may begin to shrink.