New research finds no evidence that cannabis use causes long-term cognitive decline. The finding challenges a common concern about cannabis and brain health: that using it may lead to lasting deterioration in cognitive ability. The key distinction is long-term decline. The research doesn’t mean cannabis has no cognitive effects, especially during intoxication, or that all patterns of use carry the same risks. But based on the finding reported here, researchers found no evidence linking cannabis use itself to persistent cognitive decline over time.