The Behavioral Sequelae of Cannabis Use in Healthy People: A Systematic Review

Abstract

Background: Cannabis is known to have a broad range of effects on behavior, including experiencing a “high” and tranquility/relaxation. However, there are several adverse behavioral sequalae that can arise from cannabis use, depending on frequency of use, potency (e.g., THC content), age of onset, and cumulative exposure. This systematic review examined evidence for cannabis-related adverse behavioral sequalae in otherwise healthy human subjects.Methods: Following PRISMA guidelines, we conducted a systematic review of cross-sectional and longitudinal studies from 1990 to 2020 that identified cannabis-related adverse behavioral outcomes in subjects without psychiatric and medical co-morbidities from PubMed and PsychInfo searches. Key search terms included “cannabis” OR “tetrahydrocannabinol” OR “cannabidiol” OR “marijuana” AND “anxiety” OR “depression” OR “psychosis” OR “schizophrenia” “OR “IQ” OR “memory” OR “attention” OR “impulsivity” OR “cognition” OR “education” OR “occupation”.Results: Our search detected a total of 2,870 studies, from which we extracted 124 relevant studies from the literature on cannabis effects in the non-clinical population. Effects of cannabis on several behavioral sequelae including cognition, motivation, impulsivity, mood, anxiety, psychosis intelligence, and psychosocial functioning were identified. The preponderance of the evidence suggests that frequency of cannabis use, THC (but not CBD) content, age of onset, and cumulative cannabis exposure can all contribute to these adverse outcomes in individuals without a pre-existing medical condition or psychiatric disorder. The strongest evidence for the negative effects of cannabis are for psychosis and psychosocial functioning.Conclusions: Although more research is needed to determine risk factors for development of adverse behavioral sequelae of cannabis use, these findings underline the importance of understanding vulnerability to the adverse effects of cannabis, which has implications for prevention and treatment of problematic cannabis use.

Evidence on the acute and residual neurocognitive effects of cannabis use in adolescents and adults: a systematic meta‐review of meta‐analyses

“…Although most of the evidence on the cognitive sequelae of cannabis use has been provided by cross‐sectional data associated with methodological limitations, a growing number of longitudinal studies, which are useful to address causal inferences, have emerged. This has led to several reviews examining, among others, evidence provided by prospective designed studies [20, 27, 31, 81]. For instance, Bourque et al .…”

“…Evidence pertaining to other domains, including attention and processing speed, led to more divergent findings. These reviews concluded that neurocognitive impairments may be dose‐dependent, particularly for domains related to memory [31], and effects may persist for at least 1 week when cannabis use is chronic, although these deficits are often resolved with long abstinence periods [26, 43]. Furthermore, Ganzer et al .…”

“…Indeed, experimental studies in which healthy volunteers have received varying doses of cannabinoid partial agonists have suggested negative impacts of cannabis use on executive functions, learning and memory, attention and psychomotor function, and some of these impairments may thereby be weakened with CB1 antagonists [26,28,29]. Several reviews [20,26,27,30,31] have consistently shown that the acute cannabis effects were most often reported in the domain of verbal learning and memory, although less constantly for working memory.…”

“…Several systematic reviews have examined the long-term effects of cannabis use on cognition. Broyd et al [26], Nader et al [43] and Sorkhou et al [31] identified verbal learning and memory as well as executive functions as the domains most consistently impaired with long-term cannabis use. Evidence pertaining to other domains, including attention and processing speed, led to more divergent findings.…”

“…These reviews concluded that neurocognitive impairments may be dose-dependent, particularly for domains related to memory [31], and effects may persist for at least 1 week when cannabis use is chronic, although these deficits are often resolved with long abstinence periods [26,43]. Furthermore, Ganzer et al [40] noted that findings regarding neurocognition specifically after a prolonged period of abstinence (more than 14 days) were heterogeneous.…”