The association between cannabis use and neuroimaging measures in older adults: findings from the UK biobank

Background:Cannabisusehasincreasedinrecentyears.However,thelong-termimplicationsofcannabisuseonbrainhealth remain unknown. We explored the associations of cannabis use with volumetric brain magnetic resonance imaging (MRI) measures in dementia-free older adults. Methods:Thiscross-sectionalandlongitudinalstudyincludeddementia-freeparticipantsoftheUKBiobankaged≥60years. Linear regression models were used to evaluate the associationof cannabis use and patterns of use with volumetric brain MRI measures.TheassociationbetweencannabisuseandchangeinbrainMRImeasuresovertimewasalsotested.Allmodelswere adjusted for potential confounders. Results: The sample included 19,932 participants (mean age 68±5 years, 48% men), 3,800 (19%) reported lifetime use of cannabis. Cannabis use was associated with smaller total, white, grey and peripheral cortical grey matter volumes (B=-6,690±1,157; P <0.001, B=-4,396±766; P <0.001, B=-2,140±690; P=0.002 and B=-2,451±606; P <0.001, respectively). Among cannabis users, longer duration of use was associated with smaller total brain, grey and cortical grey matter volumes (B =-7,878±2,396; P =0.001, B =-5,411±1,430; P <0.001, B=-5,396±1,254; P <0.001,respectively),andwithincreasedwhitematterhyperintensityvolume(B=0.09±0.03;P=0.008).Additionally, current vs. former users (B=-10,432±4,395; P =0.020) and frequent versus non-frequent users (B=-2,274±1,125; P=0.043)hadsmallergreyandcorticalgreymattervolumes,respectively.Nosignificantassociationswereobservedbetween cannabis use and change in brain MRI measures. Discussion: Our findings suggest that cannabis use, particularly longer duration and frequent use, may be related to smaller grey and white matter volumes in older ages, but not to late-life changes in these measures over time.