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Introduction
Many studies have reported deficits in neuropsychological function in adults with major depressive disorder (MDD; Veiel, 1997; Elliott, 1998). However, the chronicity of these deficits and their relationship with clinical and adaptive outcome has seldom been examined. There is now an increasing acknowledgement that defining recovery from depression simply in terms of an improvement in symptom load is insufficient and that indicators of remission must include a consideration of the individual's function at home, in their relationships, and in their vocation (Furukawa et al. 2001). Unfortunately there is currently little empirical data concerning these factors in early-onset depression.
Research in late-life depression has suggested a role for cognitive measures in predicting those at risk for poor outcomes (Kalayam & Alexopoulos, 1999; Alexopoulos et al. 2000; Kiosses et al. 2001). Specifically, poorer initiation/perseveration on the Mattis Dementia Rating Scale at admission predicts non-response to antidepressant medication (Kalayam & Alexopoulos, 1999), an increased risk of relapse in people who were in remission from MDD (Alexopoulos et al. 2000) and more functional dependence (Kiosses et al. 2001). Based on these well-replicated findings, Kiosses et al. (2001) recommended that an evaluation of executive function be included in routine assessments for depression in this age group.
Only two previous studies have examined the relationship between cognitive function and outcome in younger persons with MDD. Dunkin et al. (2000) conducted a small study of the relationship between executive function and clinical response to selective serotonin reuptake inhibitors (SSRIs) in 14 subjects with MDD; average age 41.9 years. Only the domain of executive function distinguished between medication responders and non-responders after controlling for differences in depression severity at baseline. Follow-up analyses identified specific deficits for non-responders on the Wisconsin Card Sorting Test (categories completed, perseverative responses and percentage conceptual level responses) and Stroop Colour Word Test interference trial. This study suggests that poor executive performance prior to treatment could be a marker for poor response to the SSRI class of drugs in younger people with MDD. Majer et al. (2004) examined a larger sample of 68 subjects with MDD (mean age 45.6 years) and found that a measure of divided attention at intake was significantly related to treatment response at follow-up. However, these findings...