A study published in Brain and Behavior found that cannabis consumption did not cause significant adverse effects on age-related cognitive decline. The study is one of the first to explore the association between cannabis use and age-related mental decline from early adulthood to late midlife.
The study included 5,162 male participants born between 1949–1961. Denmark requires all men to undergo an interview with the military conscription board between the ages of 18 and 26. Men eligible for military service take the military intelligence test called Børge Prien's Prøve.
The participants completed assessments at conscription between 1967 and 1989. At this point, the participant's mean age was 20 years. In addition, the research team also required participants to complete follow-up questionnaires focusing on lifestyle and health. The follow-up examinations were conducted in 2015–2017 and 2019–2022, when the participants had a mean age of 64. The researchers compared follow-up studies with the military intelligence test results from conscription with those from the follow-up examination. They included a comprehensive questionnaire on socioeconomic, lifestyle, and health-related factors. The team also evaluated Danish Aging and Cognition (DanACo) cohort data, which examines predictors of age-related cognitive decline from young adulthood to late midlife. The researchers used linear regression models to investigate the association between cannabis use and age-related cognitive decline.
The study indicated that men with a history of cannabis use had less cognitive decline from early adulthood to late midlife than men without a history of cannabis use. One finding showed no significant association between the age of initiation of cannabis consumption or frequency with a more significant age-related cognitive decline.
The study indicated that cannabis users demonstrated significantly less cognitive decline compared to non-users. The mean cognitive decline was 6.2 intelligence quotient (IQ) points over an average of 44 years. Cannabis users had no significant associations with age-related cognitive decline related to the initiation of cannabis use.
Sources: Brain and Behavior, NORML