A meta-analytic review of verbal fluency deficits in depression

A prominent view in the neuropsychological literature is that depression is particularly associated with deficits in executive control processes. A meta-analysis of 42 studies with 2206 participants was therefore conducted to investigate the sensitivity of tests of verbal fluency to the presence of this disorder, as there is a great deal of evidence that these measures are valid markers of executive dysfunction. When the methodology adopted by other meta-analytic reviews was employed, semantic fluency deficits were found to be substantially larger than phonemic fluency deficits. However, when a more rigorous method of meta-analysis was adopted, this indicated that the measures are in fact broadly equivalent in their sensitivity to depression, as has been found for patients with focal frontal lobe lesions. However, in contrast to patients with focal frontal lobe injuries, neither deficit qualified as a differential deficit relative to psychomotor speed. Therefore, for patients with depression, deficits on tests of phonemic and semantic fluency may not reflect executive dysfunction, but a more generalized impairment. Evidence is presented that tests of phonemic and semantic fluency may aid in the differential diagnosis of patients with depression and those in the early stages of dementia of the Alzheimer's type.