Studies are suggesting cognitive impairment for long-term users: https://www.health.harvard.edu/blog/cognitive-effects-of-lon...?
(That's not technically Alzheimer's, but it's believable someone worrying about one might worry about the other)
Studies are suggesting cognitive impairment for long-term users: https://www.health.harvard.edu/blog/cognitive-effects-of-lon...?
(That's not technically Alzheimer's, but it's believable someone worrying about one might worry about the other)
I've read that New Zealand study and it's identifying an effect in a small group of heavy users who started using cannabis very young (a full third as teens) and continue to use it heavily (four times a week) three decades later. That's not a huge surprise.
They also state "cognitive functioning among midlife recreational cannabis users was similar to representative cohort norms". It's clearly shown in Figure 1 - midlife recreational cannabis users actually got smarter than people who quit cannabis according to their data.
There may well be some confounding factor in there. The study was done in New Zealand where cannabis was illegal for the majority of participants, and usage was self-reported so there's a basic issue there as well. One of the meta-analysis citing this (Crisafulli, 2026) and finding no effect criticizes the study design.
Alzheimer's has quite high heritability. A family history seems like sufficient explanation.