Herein, we used two‐sample MR to investigate the causal relationship between drug use and different types of dementia, finding that antithrombotic agents, HMG CoA reductase inhibitors, and salicylic acid were strong risk factors for DLB; diuretics were a potential risk factor for vascular dementia; thyroid preparations and diuretics, immunosuppressants resulted as a risk factor for FTD; HMG CoA reductase inhibitors were a risk factor for dementia in Alzheimer's disease; and antihistamines for systemic use were a protective factor for cognitive performance. This evidence concerns the gene HMGCR and early-onset autosomal dominant Alzheimer disease.