For example, some genes related to immune regulation and inflammation may be associated with Alzheimer's disease or depression (e.g., IL10 and IL1B), genes of the dopamine neurotransmitter system (e.g., DRD1 and DRD4), and members from the immunophilin protein family (e.g., FKBP4 and FKBP5) that may be associated with Alzheimer's disease or depressive disorders. Here, DRD1 is linked to early-onset autosomal dominant Alzheimer disease.