Cognitive impairment of medicated patients with remitted depression and low anticholinergic activity

A recent meta-analysis has found that patients who have achieved remission of major depressive disorder (MDD) show cognitive dysfunction. Moreover, anticholinergic activity levels are associated with cognitive dysfunction, although the extent of these effects is unclear. Therefore, we measured serum anticholinergic activity (SAA) in blood samples of patients with remitted MDD and examined its relationship with cognitive function.

We recruited 49 patients with remitted MDD following treatment and 165 healthy subjects. Subjects completed the Stroop test and the logical memory (LM) and visual reproduction (VR) subtests from the Wechsler Memory Scale-Revised. We compared cognitive function scores among those with SAA below the limit of quantification (SAA [-]), those with SAA above the limit of quantification (SAA [+]), and healthy controls.

The SAA (+) group scored significantly lower (p < 0.001) than the healthy control group on all tests, and the VR score of the SAA (-) group was significantly lower than that of the healthy control group (p = 0.024). LM scores in the SAA (+) group were significantly lower than that of the SAA (-) group (p = 0.033). Multiple regression analysis revealed a significant effect of SAA on the LM score (p = 0.015).

Our study was a cross-sectional analysis of a small number of patients.

Our results support previous findings that the anticholinergic effect of antidepressants adversely affects cognitive function. Additionally, the cognitive impairment observed may persist because of MDD.