Background: Despite the robust and widely replicated finding of elevated hypothalamic-pituitary-adrenal (HPA) axis reactivity in depressed adults, studies of depressed children have yielded ambiguous findings. Animal models of early depression and studies of children experiencing early psychosocial deprivation have suggested that alterations in HPA axis reactivity are evident in early "depressive-like" conditions. The current study is, to our knowledge, the first investigation of HPA axis reactivity in very young children with a clinical depressive syndrome for which content validity has been established.
Methods: Depressed, psychiatric, and no-disorder comparison children aged 3 through 5.6 years were studied for HPA axis reactivity in response to experimental psychosocial stressors. The children were diagnosed using a developmentally appropriate, structured psychiatric interview. Salivary cortisol was obtained at 3 time points during a laboratory assessment before and after stressors involving separation from the parent and frustrating tasks.
Results: Repeated measures of multivariate analysis of variance revealed a significant interaction between the diagnostic group and 2 cortisol percent change scores. Depressed preschoolers displayed a pattern of increasing cortisol levels throughout the assessment in response to both separation and frustration stressors. In contrast, both comparison groups showed decreasing cortisol levels in response to the separation stressor. All groups displayed increasing cortisol levels in response to frustrating tasks. Preschoolers with a presumptive melancholic depressive subtype displayed these alterations at a greater magnitude relative to comparison groups.
Conclusions: To our knowledge, these findings are the first to demonstrate altered HPA axis reactivity in depressed preschoolers. These alterations are consistent with those described in depressed adults and in animal models of early depression. These findings provide evidence for possible continuity of HPA axis alterations in depressive disorders across the lifespan and are discussed in the context of prior studies of HPA axis reactivity in clinically depressed children and adolescents, suggesting that younger age and inpatient status are features associated with altered HPA axis reactivity.