Preschool Depression and Hippocampal Volume: The Moderating Role of Family Income

Abstract

Objective: Depression and low socioeconomic status have both been associated with hippocampal volume alterations. Whether these factors interact to predict neurobehavioral outcomes has not been adequately studied. The authors investigated family income as a moderator of the relationship between depression and hippocampal volume in a longitudinal sample.

Method: Longitudinal behavioral data, beginning at preschool age, and behavioral and neuroimaging data from school age to adolescence were used to assess the impact of preschool only and total preschool to adolescent depression symptoms on hippocampal volumes using family income as a moderator (N = 176).

Results: Depression severity during the preschool period interacted with family income to predict hippocampal volumes at the intercept (ie, age 13 years; B = -0.078, p = .003). Interaction decomposition revealed that only individuals with relatively high family income exhibited smaller hippocampal volume with increasing depression severity (B = -0.146, p = .005). Family income was associated with hippocampus volumes only in individuals with low to moderate preschool depression severity (B = 0.289, p = .007 and B = 0.169, p = .030, respectively).

Conclusion: Preschool depression severity interacts with family income to predict hippocampal volume across development, such that the effects of early depression are evident only in those with higher income. These findings suggest that hippocampal volume may not be an effective marker of risk for depression at different levels of socioeconomic status, and emphasizes the importance of the environmental context when assessing risk markers for depression. Future research should explore how socioeconomic stress may eclipse the effects of depression on hippocampal development, setting alternative neurodevelopmental risk trajectories.

Keywords: hippocampus; poverty; preschool depression; structural MRI.

Figure 1:. Bilateral Hippocampus Volume as a Function of Major Depressive Disorder (MDD) Symptoms and Family Income-to-Need Ratio

Note: Estimated trajectories from a multilevel model of hippocampus volume at scans 1–5 by preschool MDD severity and family income-to-needs ratio (INR). Separate lines for −1, 0, and +1sd from the sample INR mean are for visualization purposes only. All analyses treated MDD severity and family INR as continuous variables. Model predictions presented are from a conditional interaction and represent predicted hippocampal volumes at 13-years-old, which is the median age of the sample.