Is there evidence for cannabis in Alzheimer's disease and dementia?

Alzheimer's disease (AD) involves amyloid-beta plaques, tau tangles, neuroinflammation, and progressive neurodegeneration. The ECS connection: CB1 and CB2 receptors are expressed on neurons and microglia throughout the brain; CB2 is upregulated in activated microglia surrounding amyloid plaques in AD brains. Preclinical evidence is compelling: THC reduced amyloid-beta aggregation and tau phosphorylation in cell studies; CBD reduced neuroinflammation and promoted neurogenesis in AD mouse models; combined THC+CBD improved memory in AD mice. Clinical evidence is very limited: a 2019 RCT (van den Elsen et al., n=50) found dronabinol (1.5mg twice daily) did not significantly improve agitation in dementia patients vs. placebo. A 2021 pilot study found nabilone reduced agitation in AD. For behavioral symptoms (agitation, aggression, sleep disturbance) in dementia — where antipsychotics carry serious risks — cannabinoids represent a potentially safer alternative, though evidence remains insufficient for recommendations. No trials have examined disease-modifying effects in humans.