Depression and Physical Illness: A Multiwave, Nonrecursive Causal Model

Abstract

Causal influence has frequently been assumed, but rarely demonstrated, in studies documenting a positive association between physical illness and psychological distress. The present study assesses a latent variable causal model of subjectively experienced physical illness and depression in order to disentangle reciprocal patterns of influence. The data consist of interviews from a community sample of adults (N = 744) interviewed four times over one year. For the total sample, the exogenous variables of socioeconomic status, age, and sex are shown to affect both constructs of physical illness and depression. Illness has a large, contemporaneous effect of increasing depressive symptomatology over previous levels, and depression is found to have a smaller, 4-month lagged effect of increasing levels of physical illness. Multiple group analyses reveal some differences by age and sex, but demonstrate an overall consistency in the reciprocal relationship between depression and physical illness.