Marijuana matters: reviewing the impact of marijuana on cognition, brain structure and function, & exploring policy implications and barriers to research

Abstract

The neurobiologic effects of cannabis, commonly referred to as 'marijuana' (MJ), have been studied for decades. The impact of recreational MJ use on cognition and measures of brain function and structure is outlined, and variables influencing study results are discussed, including age of the consumer, patterns of MJ use, variations in MJ potency, and the presence of additional cannabinoids. Although evidence suggests that chronic, heavy recreational MJ use is related to cognitive decrements and neural changes, particularly when use begins in adolescence, findings from studies of recreational MJ users may not be applicable to medical marijuana (MMJ) patients given differences in demographic variables, product selection, and reasons for use. Although additional research is needed to fully understand the impact of MJ and individual cannabinoids on the brain, current findings are beginning to inform public policy, including considerations for age limits, potential limits for some cannabinoids, and guidelines for use. However, barriers continue to impede researchers' ability to conduct studies that will guide policy change and provide vital information to consumers and patients regarding best practices and safest methods for use. The need for information is critical, as legalization of MJ for medical and recreational use is increasingly widespread.

Cannabis effects on brain structure, function, and cognition: considerations for medical uses of cannabis and its derivatives

“…Although evidence suggests that heavy, recreational cannabis use is linked to cognitive deficits and potentially untoward neural changes as outlined above, findings from studies of recreational cannabis use may not be applicable to medical marijuana (178). One study examined whether patients receiving medical marijuana would exhibit improvement in cognitive functioning, perhaps related to primary symptom alleviation (179).…”

Implications of Medical and Recreational Marijuana Laws for Neuroscience Research: a Review

“…Behaviors such as use and misuse of illicit substances often cluster empirically within the externalizing domain of psychopathology [78][79][80][81], typically with early onset, common etiology, and traits including sensation-seeking and impulsivity [82][83][84]. People who are recreational cannabis users seeking the sensation of feeling high are likely to differ from people who are medical patients [85,86] seeking marijuana for relief of pain or other symptoms and who are not typically characterized by externalizing traits [87,88]. People who are medical marijuana users may therefore differ in numerous ways from people who are recreational users in whom cognitive effects have mainly been studied to date, including later onset of use and complicating medical problems.…”

The effects of cannabis use on cognitive function in healthy aging: A systematic scoping review

“…Cannabis impairs cognition in young people, likely attributable to the detrimental effects of THC on the developing brain (Broyd et al, 2016; Crane et al, 2013; Gorey et al, 2019; Scott et al, 2018). The effects of cannabis use on cognition in middle-to-older-aged adults may be complicated however, by a number of age-related factors, including: (1) An increased selection of high-CBD cannabis, which has anti-inflammatory properties (Burstein, 2015; Mori et al, 2017) and may attenuate the cognitive impacts of low-grade inflammation seen in aging (Fard & Stough, 2019; Patterson, 2015); (2) a slowing of the metabolism, resulting in extended periods of intoxication (Sagar & Gruber, 2018); and (3) age-related changes in the dopamine system (Karrer et al, 2017), which is instrumental in several cognitive domains affected by age including reward-based decision making (Berry et al, 2019), and affected by cannabis use (Yoo et al, 2019). Ultimately, the proliferation of cannabis use among middle-to-older-aged adults who may already be susceptible to cognitive decline and the known detrimental effects of cannabis on cognitive function in young people, highlights the need to examine the effects of cannabis use on cognitive function among middle-to-older-aged adults.…”