Neuropsychological performance in melancholic, atypical and undifferentiated major depression during depressed and remitted states: a prospective longitudinal study

Background: Considerable evidence has demonstrated that melancholic and atypical major depression have distinct biological correlates relative to undifferentiated major depression, but few studies have specifically delineated neuropsychological performance for them.

Method: In a six-week prospective longitudinal study, we simultaneously compared neuropsychological performance among melancholic depression (n=142), atypical depression (n=76), undifferentiated major depression (n=91), and healthy controls (n=200) during a major depressive episode and a clinically remitted state, respectively. We administered neuropsychological tests assessing processing speed, attention, shifting, planning, verbal fluency, visual spatial memory, and verbal working memory to all participants.

Results: During the depressive state, the three subtypes displayed extensive cognitive impairment, except for attention, when compared with the healthy controls. Melancholic depression significantly differed from atypical depression in processing speed and verbal fluency. In the remitted state, the three subtypes recovered their visual spatial memory and verbal working memory functions to the healthy control level. The recovery of the other domains (processing speed, set shifting, planning, and verbal fluency), however, was different across the subtypes. No predictive relationship existed between neuropsychological performance and the treatment outcome.

Limitations: The drop-out rate in the six-week longitudinal study was relatively high.

Conclusion: Our data provide preliminary evidence that during depressed states the three major depressive subtypes display similar cognitive deficits in some domains but differ in such domains as processing speed and verbal fluency. The recovery of the cognitive deficits following clinical remission from depression may be associated with subtypes of major depressive disorder.