Executive function and short-term remission of geriatric depression: the role of semantic strategy

This study tested the hypothesis that use of semantic organizational strategy in approaching the Mattis Dementia Rating Scale (MDRS) complex verbal initiation/perseveration (CV I/P) task, a test of semantic fluency, is the function specifically associated with remission of late-life depression.

Seventy elders with major depression participated in a 12-week escitalopram treatment trial. Neuropsychologic performance was assessed at baseline after a 2-week drug washout period. Patients with a Hamilton Depression Rating Scale Score ≤7 for 2 consecutive weeks and who no longer met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria were considered to be remitted. Cox's proportional hazards survival analysis was used to examine the relationship between subtests of the I/P, other neuropsychologic domains, and remission rate. Participants' performance on the CV I/P subscale was coded for perseverations, and use of semantic strategy.

The relationship between the performance on the CV I/P subscale and remission rate was significant. No other subtest of the MDRS I/P evidenced this association. There was no significant relationship between speed, confrontation naming, verbal memory, or perseveration with remission rate. Remitters' use of verbal strategy was significantly greater than nonremitters.

Geriatric depressed patients who showed decrements in performance on a semantic fluency task showed poorer remission rates than those who showed adequate performance on this measure. Executive impairment in verbal strategy explained performance. This finding supports the concept that executive functioning exerts a "top down" effect on other basic cognitive processes, perhaps as a result of frontostriatal network dysfunction implicated in geriatric depression.