A recent study using the THINC-it® tool in patients with major depression found an association between subjective cognitive dysfunction and psychosocial impairment. Objective cognitive function did not show the same relationship. The implication is that both subjective and objective cognitive impairment should be measured if we want to fully understand the functional implications of depression.
Psychosocial impairment can persist in patients with major depressive disorder (MDD) even when the core symptoms of depression have improved or resolved,1 and residual psychosocial impairment is a risk factor for depressive relapse.
With respect to cognitive impairment, growing epidemiological and clinical evidence suggests this aspect of MDD is a critical determinant of functional outcomes.2 But there may be discordance between subjectively reported cognitive impairment and impairment that is objectively measured.
Thus, Danielle Cha (University Health Network, Toronto, Canada) and colleagues studied the association between objective and subjective cognitive impairment on the one hand and impaired psychosocial function on the other, taking into account the influence of depression severity.
One hundred patients with moderate to severe MDD (Montgomery-Åsberg Depression Rating Scale [MADRS] score of 22 or greater) that had lasted for at least 3 months were compared against 100 healthy control individuals (with no past or present psychiatric disorder) matched for age, sex and education.
Subjective cognitive impairment was significantly associated with psychosocial impairment independent of depression severity scores.
Cognitive function was assessed using the newly validated THINC-it® tool, which includes objective and subjective measures of impairment.3 This free, computerised battery reliably detects impairment in MDD. Objectively measured items from THINC-it® were used to calculate overall objective cognitive function. Self-reported cognitive impairment was derived from the Perceived Deficits Questionnaire for Depression 5-item version (PDQ-5-D), which is included in the THINC-it® battery.
The Sheehan Disability Scale (SDS) was used to measure subjective psychosocial function. The SDS has subscales covering three discrete domains of function: work/school; social life; and family life/home responsibilities. Severity of depression was assessed using the MADRS.
Major findings
After controlling for age, sex and education, patients with MDD reported significantly greater impairment than healthy control individuals in psychosocial function. This was reflected in overall score on the SDS and in the scores on all three subscales.
People with MDD showed significant impairment on the THINC-it® composite score of objective cognition, and they also had poorer self-reported cognition using the PDQ-5-D. Compared to healthy control individuals, patients with MDD reported that they had spent more days being economically unproductive or under-productive.
THINC-it® allows for a holistic understanding of cognitive impairment.
Taking into account depression severity, the extent of patients’ subjective cognitive impairment was significantly related to self-reported impairment of psychosocial function and to number of economic days lost. Interestingly, the overall THINC-it® measure of objective cognitive dysfunction was not related to subjective psychosocial impairment or to lost productivity.
Since objective and subjective cognitive impairment seem to relate differently to psychosocial function in patients with MDD, Danielle Cha and colleagues conclude that both should be assessed. Importantly, they also reinforce the view that psychosocial impairment should be a target of treatment, since a major aim of people with MDD is to return to normal pre-depression functioning.
