Cognitive impairment as a mediator in the developmental pathway from infant malnutrition to adolescent depressive symptoms in Barbadian youth

Abstract

Objective: Depressive symptoms are elevated in adolescents who experienced significant malnutrition early in life. Early malnutrition can also have a significant impact on cognitive functioning, presumably because of the adverse impact of the malnutrition on the very young brain. In the context of a developmental cascade model, we tested the hypothesis that the association between early malnutrition and adolescent depressive symptoms is mediated by the cognitive impairment that ensues from the malnutrition.

Methods: We evaluated Barbadian youth (N = 57) hospitalized for moderate to severe protein-energy malnutrition in the first year of life and healthy controls (N = 60) longitudinally. The primary hypothesis was tested by multiple regression models.

Results: After adjusting for covariates, early malnutrition predicted both cognitive functioning in childhood (IQ, p < .001; attention problems, p < .01; Common Entrance Examination, p < .01; and adolescent depressive symptoms, p < .05). Childhood cognitive functioning mediated the association between early malnutrition and depressive symptoms in adolescence (p < .001). Maternal depressive symptoms were a significant but independent predictor of adolescent depressive symptoms (p < .05).

Conclusions: Cognitive compromise in childhood accounts indirectly for elevated depressive symptoms in previously malnourished adolescents, consistent with a developmental cascade model. The direct link between malnutrition and depressive symptoms in adolescence is small.

Figure 1

(a) Simple model showing early malnutrition leads to depressive symptoms in adolescence. (b). Hypothetical model showing that malnutrition affects IQ and school behavior (attention) which in turn affects performance on the CEE which then affects depressive symptoms in adolescence. Model also provides for direct effect of malnutrition on adolescent depressive symptoms as well as direct effects of IQ and attention on depressive symptoms.

Figure 2

Study design showing 3 groups of participants in the Barbados Nutrition Study and age ranges at each time point. Kwashiorkor group (dotted line) was not included in the present study because longitudinal data were not available. N is reduced at T3 for Marasmus and Healthy Comparison groups because they were selected as controls for the 62 children in the Kwashiorkor group.

Figure 3

Final model showing that the cognitive variables (IQ, attention and Common Entrance Examination) mediate the developmental pathway from early malnutrition to adolescent depressive symptoms. Standard of living is included in the model, having direct effects on malnutrition and cognitive measures but not depressive symptoms. Maternal depression has a direct effect on adolescent depressive symptoms but does not mediate path from infant malnutrition to adolescent depressive symptoms.