Depressive Behaviors and Inflammation in Preschool-Aged Children

Symptoms of depression, including sadness, irritability, loss of interest in activities, changes in sleep patterns, eating, and weight, and impairment in functioning, can emerge in early childhood and persist throughout the lifespan. However, distinguishing symptoms from typical behaviors of early childhood (e.g., sadness, irritability) is challenging. In addition to contributing to distress and impairment, depression is also associated negative physiological correlates. Psychosocial stressors such as depression can stimulate activation of immune responses. Specifically, people affected by depression experience longer healing times after injury, higher frequency of illness, and chronic inflammation. An association between chronic immune function dysregulation and depressive symptoms has been consistently found in research with adults, adolescents, and school-aged children. However, the relationship between depression and dysregulated inflammatory processes has not been investigated in young children. This study investigated an association between depressive behaviors and two inflammatory markers, interleukin 6 and interleukin 1 beta, in preschool-aged children. Measures included parent-report daily diaries to assess depressive behaviors and questionnaires to assess irritability, impairment, and health and sickness history in their children; laboratory-assessed negative emotionality (NA); and inflammatory markers measured via children’s saliva. It was hypothesized that higher levels of depressive behaviors, impairment, sickness, and negative emotionality would be associated with higher levels of inflammation in preschool-aged children. Additionally, this association was examined in exploratory analyses to identify the specific frequencies of depressive behaviors linked to inflammation. Results revealed no significant relations between depressive behaviors and inflammation, but found significant associations among chronic and acute sickness and depressive as well as demographic variables. Additionally, girls were more likely to experience acute illness than boys. No significant associations were found among other study variables. These findings suggest that the mechanism responsible for the association between depression and inflammation identified in older youth and adults may yet not be present or active in preschool-aged children. Future studies should continue to explore this association in young children as well as the acute immune response to depressive behaviors. These efforts can contribute to the broader goal of delineating typical, normative behaviors in early childhood from clinically significant behaviors to identify potential risk for the development of depression.