The effect of age on frontal lobe related cognitive functions of unmedicated depressed patients

Aging is associated with a decline in frontal lobe related cognitive functioning of healthy subjects (i.e., executive functioning and higher-order cognition). Unipolar depression is associated with dysfunctions in similar cognitive domains--deficits that impact the functioning and quality of life of these patients. The effect of age on frontal lobe related cognitive functions of depressed patients, however, has not been adequately studied. The current study therefore assessed a wide age range of depressed patients and compared their frontal lobe related cognitive functions to that of matched healthy controls. Recruitment of unmedicated patients minimized the confounding effect of psychiatric medications.

Depressed patients and healthy controls were divided into three age groups (<25, 25-45, and 46-65 years of age) and matched in gender, age and education level (N total=170). Cognition was assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB).

The depressed patients had deficits in cognitive planning/organization, working memory, and sustained attention compared to the healthy controls. Aging was associated with a decrease in frontal lobe related functioning. Except for working memory, no significant interactions were found between the age groups and the study group (depressed/healthy).

Depressed patients are impaired in most domains of frontal lobe related cognitive functions. These deficits are already evident at an early age and persist in older age cohorts (despite an overall age related decline). These findings may help clarify the profile and course of cognitive deficits among depressed patients while providing tentative support for a developmental model of cognitive impairment in depression.