Life-Course Prospective Inquiry
Life-Course Prospective Inquiry
One of the most powerful methods in developmental clinical research is that of life-course prospective inquiry, closely linked to developmental epidemiology. By identifying an important sample (either a high-risk sample or a representative sample) and then following that sample with repeated assessments across time using hypothesis-driven measures, researchers have been able to identify risk factors in the development of a disorder, moderators of that risk, and mediating processes in the etiology of the disorder. Two such longitudinal studies are described in this section as examples of ongoing research in this field.
The Development of Depression Project
The Development of Depression Project has tested the diathesis-stress model of the development of major depressive disorder in adolescents. According to Garber, some children develop cognitive styles for attributing their failures and losses to internal, global, and stable characteristics of themselves, and they begin to have negative automatic thoughts in response to life events. Later, when confronted with failures and losses, these children are at elevated risk for developing major depressive disorder. It is the interaction of the cognitive diathesis and the life stressor, not either factor in isolation, that leads to depression. In order to rule out competing hypotheses that cognitive styles or problem life events result from, rather than lead to, depression, a research design is needed that follows children across time.
The research strategy in this study was to identify a sample of children prior to adolescence; to assess cognitive diatheses, life events, family processes, and psychopathology in this sample at that time; and then to follow the children with repeated assessments throughout adolescence in order to determine which ones develop depression following common stressors of adolescent life. The pool of subjects came from three entire cohorts of fifth-grade children in the Nashville, Tennessee, public schools. In order to ensure that the ultimate prevalence rate of major depressive disorder in the research sample was high enough to conduct statistical tests of hypotheses, written and telephone screening of 1495 families, followed by Structured Clinical Interviews for Diagnoses, was used to identify 188 offspring of parents with a life history of depression. This high-risk sample was complemented by an additional 53 low-risk offspring of parents with no psychopathology. Thus the design is not strictly epidemiologic because the community population is not representatively sampled; rather, it is a prospective high-risk sample design aimed at testing specific theoretical hypotheses of a developmental psychopathologic process.
At the first wave of assessment in sixth grade, children and parents were assessed for psychopathology, life events stressors, family processes, and most pertinent, the cognitive diathesis for depression. Analyses of the initial wave revealed that children of depressive parents demonstrated more subthreshold symptoms of depression and more negative attributional styles than did the children of nondepressed parents. Even though these findings are consistent with the hypothesized model, the critical test would come over time if initial depressive symptom levels could be controlled statistically to see whether attributional styles and life stressors interact to predict onset of depressive disorder. All children have been followed annually through 12th grade with repeated assessments using a contextual threat life events interview and structured psychiatric interviews. Analyses indicate that among those children who displayed at least some depressive symptoms, controlling for initial depressive symptom levels, the interaction of early cognitive diathesis and subsequent stressful life events significantly predicted later depressive symptom levels as determined by psychiatric interviews. That is, only those children with a combination of initial negative automatic thoughts and subsequent stressful life events showed elevated depressive symptoms later; all other groups showed lower levels of symptoms. This is a moderator effect: The cognitive diathesis moderates (or alters) the effect of stressful life events on depressive symptoms.
How do cognitive diatheses for depression develop? Garber hypothesized that family processes might be responsible. At the initial wave of assessment, she measured parental control and lack of acceptance. Later she found that these aspects of family process predicted both cognitive diatheses and later depressive symptoms in children. Consistent with the mediation hypothesis, she also found that the child’s cognitions, especially feelings of negative self-worth, mediated (or statistically accounted for) part of the effect of family interactions on the child’s depressive symptoms.
This prospective study has provided empirical support for a model in which early family interactions involving psychological control and lack of acceptance lead a child to develop cognitive styles of negative self-worth, negative automatic thoughts, and negative attributions for failure. Later, in adolescence, those children who show the unique combination of experiencing stressful life events and having negative automatic thoughts about those events are most likely to develop depression. This model integrates biological (genetic risk), family process, cognitive, and ecological (stressful life events) factors in the onset and course of depression. It also suggests three points for intervention with children who are at risk for depression. First, early family interactions involving acceptance and control might be targeted through parent training. Second, the child’s cognitive styles might be addressed in brief preventive cognitive therapy. Third, the child’s ecology might be modified by altering the child’s exposure to stressful life events (or at least the child’s experience of inevitable stressful events).