Inhibitory deterioration may contribute to hallucinations in Alzheimer's disease

Introduction. Although delusions and hallucinations are relatively common symptoms in individuals with Alzheimer's disease (AD), very little is known regarding underlying mechanisms. We examined whether these manifestations could be underpinned by psychological distress and executive impairments. Methods. Thirty-one participants with probable mild AD and 33 healthy older adults were administered a neuropsychological and clinical battery assessing delusions, hallucinations, anxiety, depression, episodic memory and executive functions (shifting, updating and inhibition). Results. Prevalence of delusions and hallucinations were significantly higher in AD participants compared to control participants. Further, hallucinations in AD participants were significantly correlated with poor inhibition, with the latter uniquely predicting the former, as compared to other variables. In addition, hallucinations in AD participants were associated with depression, a relationship that was further mediated by inhibition. Conclusion. Hallucinations in individuals with AD seem to be related to difficulties suppressing irrelevant thoughts, resulting in these irrelevant thoughts becoming confused with ongoing reality.