HMGCR and Alzheimer disease: Through an MR approach, our study systematically screened the potential causal associations between clinical medications and major NDs, indicating negative causal associations between immunosuppressants, antihypertensives, and thyroid preparations and AD risk, negative causal associations between immunosuppressants, glucocorticoids, and thyroid preparations and PD risk, and positive causal associations between HMG CoA reductase inhibitors, antithrombotic agents, and salicylic acid derivatives and ALS risk.