Depressive symptoms can account for 19.5% to 43.7% of the association between the cognitive performance of middle-aged adults and later levels of functioning, according to a study published in the Journal of Clinical Psychiatry.

Using data from CONSTANCES, a large-scale, population-based study in France, investigators sought to evaluate the possible associations between baseline depressive symptoms and cognitive functioning of middle-aged adults (≥45 years) and later levels of functioning. Participants (N=7426) completed the following baseline tests between February 2012 and December 2013: the Digit Symbol Substitution Test (DSST), the Semantic Verbal Fluency (SVF) test, the Trail Making Test part B (TMT-B), and the Center for Epidemiologic Studies Depression Scale (CES-D).

In 2014, participants were sent the second version of the Short-Form–12 Health Survey (SF-12v2), with a mean follow-up time between baseline and assessment of 497±157 days. The 2 subscales used as primary study outcomes were social functioning (range, 1-5) and role limitations (range, 2-10), with higher scores corresponding with higher functioning. Mediation analysis and general linear models — including age, sex, alcohol intake, cannabis use, and education levels as covariates — were used to examine the association between functioning at follow-up and baseline cognitive performance and depressive symptoms.

Depressive symptoms were significantly associated with cognitive scores at baseline: TMT-B (β=0.15; 95% CI, 0.08-0.21; P <.001), DSST (β=−0.19; 95% CI, −0.25 to −0.13; <.001], and SVF (β=−0.11; 95% CI, −0.17 to −0.04; P =.001). Baseline depressive symptoms were able to predict level of functioning at follow-up: role limitations (β=−1.10; 95% CI, −1.16 to −1.03) and social functioning (β=−1.02; 95% CI, −1.08 to −0.96]. Baseline cognitive functioning scores were also indicative for role limitations (TMT-B [β=−0.11; 95% CI, −0.13 to −0.08], DSST [β=0.11; 95% CI, 0.09-0.14], and SVF [β=0.03; 95% CI, 0.01-0.06]) and social functioning (TMT-B [β=-0.08; 95% CI, −0.11 to −0.06], DSST [β=0.10; 95% CI, 0.07-0.12], and SVF [β=0.04; 95% CI, 0.01-0.05]).

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Only 0.3% to 1.4% of the association between depressive symptoms and level of functioning could be accounted for by cognitive performance whereas 19.5% to 43.7% of the relationship between cognitive performance and level of functioning could be accounted for by depressive symptoms.

Study investigators concluded that “[i]n middle-aged adults from the general population with depressive symptoms, cognitive impairment is unlikely to substantially explain altered functioning… Interventions aimed at reducing the functional impairment associated with depression should primarily target depressive symptoms themselves; such interventions are likely to improve cognitive functioning at the same time.”

Reference

Vulser H, Wiernik E, Hoertel N, et al. Depression, cognitive functions, and impaired functioning in middle-aged adults from the CONSTANCES cohortJ Clin Psychiatry. 2018; 79(6).