Cognitive impairment in patients clinically recovered from central nervous system depressant drug overdose

CNS-depressant drugs (CNS-Ds) are known to impair cognitive functions. Overdose of these drugs is common and the majority of the hospital-treated patients are discharged within 24–48 hours. No previous studies have examined whether they have residual impairment at the time of discharge. Our aim was to evaluate whether patients with CNS-D overdose are impaired in cognitive domains important in daily activities at that time. We compared visuomotor skills (Trail-Making A and choice reaction time), executive functions (viz. attentional set-shifting: Trail-Making B, and planning: Stockings of Cambridge task [SOC] from the Cambridge Neuropsychological Test Automated Battery [CANTAB]), working memory (Letter-Number Sequencing) and impulsivity and decision-making (CANTAB Information Sampling) in 107 patients with CNS-D overdose (benzodiazepines, opioids or antipsychotics) with a Control Group of 68 with non-CNS-D overdose (acetaminophen, SSRI and SNRIs) on discharge from hospital. Outcome measures were adjusted for demographic and clinical covariates in multivariate regression models. Compared to the Controls, the CNS-D Group was significantly impaired in all domains: they had prolonged Trail-Making completion times and reaction times, poorer working memory and planning and were more impulsive in decision-making. Their SOC performance was comparable to the Control Group for simple problems but worsened with increasing task complexity. The results show that patients with CNS-D overdose could be impaired in multiple cognitive domains underlying everyday functioning even at the time they are deemed medically fit to be discharged. Such impairments could adversely affect social and professional lives of this relatively young population during the immediate post-discharge period.