Objectives: Some, but not all, studies have found prior depression to predict later cognitive decline (CD). To date, little research has investigated whether certain subtypes of depression are more disposed to CD. We identified melancholic depression as a subtype that would be related to CD because it has been uniquely associated with hyperactivation of the HPA axis, and, potentially, damage to the hippocampus (an important memory center in the brain). We contended that older depressed patients meeting criteria for melancholic depression would experience greater decline on a global measure of cognitive functioning compared to older patients with non-melancholic depression and non-depressed older adult control participants.
Method: Participants were 248 depressed patients and 147 healthy controls 60 years and older enrolled in the NCODE study (155 melancholic, 93 non-melancholic, 147 controls). Data were drawn from four times points, each one year apart. The Mini Mental Status Examination (MMSE) measure of cognitive functioning was administered yearly, and covariates (age, depression severity, and psychomotor agitation) were measured at baseline.
Results: Unfortunately, our hypotheses were not supported. Controlling for age, depression severity, and psychomotor agitation, those with melancholic depression did not experience greater CD compared to those with non-melancholic depression or healthy controls.
Discussion: The treatment of the depressed patients with medication may have potentially obscured our results.
