Critical flicker fusion threshold and anticholinergic effects of chronic antidepressant treatment in remitted depressives

The persistence of deficits in cognitive performance in major depressive patients taking maintenance antidepressant medication was assessed by examining groups of patients in clinical remission, stable on one of a range of tricyclics or selective serotonin re-uptake inhibitors (SSRIs) for at least 3 months, compared with controls. Measures of critical flicker fusion (CFF), choice reaction time (CRT), subjective sedation, and anticholinergic side-effect score were made. Tricyclic antidepressants (TCAs) produce a significant deficit in critical flicker fusion threshold compared both to controls and SSRIs. Similar effects were seen with choice reaction times which were significantly affected by age. Sedation scores were significantly higher with TCAs than SSRIs. Anticholinergic side effects were strongly related to CFF, less so to visual analogue sedating scales and not significantly to CRT. The effect measured by CFF is different from sedation, and may be related to the anticholinergic potency of the drug; it may be considered a drug-induced pseudodementia. This effect represents a risk factor for accidents during maintenance therapy and may impair work and leisure performance. The relative risk of weight gain with TCAs compared to SSRIs in women was 5.92 (95% CI 1.79-19.50).