Cognitive impairment in studies of 5HTTLPR and psychosis in Alzheimer's disease: a systematic review.

BACKGROUND/AIMS Cognitive impairment is a well-established correlate of psychotic symptoms in Alzheimer's disease (AD-P). We review whether this relationship has confounded previous genetic association studies of 5HTTLPR and AD-P. METHODS We reviewed all studies on 5HTTLPR and conducted a semi-quantitative analysis. RESULTS Three out of 4 studies with low MMSE reported a significant association, while 1 out of 4 with high MMSE reported a significant association. CONCLUSIONS Variation in cognitive impairment in past studies has contributed to the inconsistency in findings. The findings presented here bring a greater clarity to our understanding of the role of 5HTTLPR in AD-P.