Table 1.
Review of evidence for acute and chronic effects of cannabis use on behavioral outcomes.
| Behavioral Outcome Measured | Negative Effects | References | Positive or Neutral Effects | References | Conclusions |
|---|---|---|---|---|---|
| Verbal, Episodic, and Working Memory (N = 37) | There is evidence that acute and chronic cannabis use beginning in adolescence is associated with impairments in working memory, episodic memory, and verbal learning | (13, 24, 35–56) | Other evidence suggests that cannabis use is not associated with impairments in episodic memory, verbal working, or verbal learning | (14, 35, 56–66) | Overall, there is a moderate level of evidence implicating a negative relationship between cannabis use and verbal, working, or episodic memory. A total of 24/37 (64.9%) of included studies assessing these behavioral sequelae observed a negative effect of cannabis use |
| Visuospatial Memory (N = 6) | Only one experimental study found that THC administration corresponds with impairment in visuospatial memory | (41) | Most evidence suggests that cannabis use is not associated with impairments in visuospatial memory or visuospatial working memory | (40, 66–70) | There is little evidence implicating a relationship between cannabis use and impairments in visuospatial memory. Only 1/6 (16.7%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Attention (N = 20) | There is evidence that chronic cannabis use is associated with impairments in divided attention and sustained attention | (36, 40, 53, 64, 70–77) | Other evidence that chronic cannabis use is not associated with impairments in selective attention | (35, 44, 48, 57, 62, 66, 78, 79) | Overall, there is a moderate level of evidence implicating a negative relationship between cannabis use and attention. 12/20 (60%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Processing Speed (N = 6) | There is evidence that cannabis use and acute THC intoxication is associated with impairments in information processing | (36, 64, 72) | There is other evidence that chronic cannabis use does not lead to impairments in information processing | (56, 63, 65) | Overall, there is a mixed level of evidence implicating a negative relationship between cannabis use and processing speed. 3/6 (50%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Executive Function (N = 20) | There is evidence from multiple study designs that cannabis use is associated with impairments in executive functioning, decision-making, and planning | (35, 47, 49, 74, 77, 80–86) | There is other evidence that chronic cannabis use does not impair executive functioning | (44, 48, 62, 65, 66, 87–89) | There is a moderate level of evidence implicating a negative relationship between cannabis use and executive function. 12/20 (60%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Impulsivity/Inhibitory Control (N = 17) | There is evidence that acute THC intoxication and cannabis use beginning in adolescence is associated with greater impulsivity or impairments in inhibitory control | (41, 44, 48, 63, 71, 74, 90–93) | However, some studies assessing acute THC intoxication or chronic cannabis use in adults is not associated with greater impulsivity or impairments in inhibitory control | (35, 38, 56, 70, 94–96) | There is a mixed level of evidence implicating a negative relationship between cannabis use and inhibitory control. 10/17 (58.8%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Intelligence (IQ) (N = 7) | There is some evidence that cannabis use beginning in adolescence is correlated with a minor decrease (1–2 points) in IQ in adulthood | (47, 55, 86) | Other evidence suggest that chronic cannabis use does not impact global IQ in adulthood after adjusting for potential confounds | (42, 97–99) | There is a mixed level of evidence implicating a negative relationship between cannabis use and intelligence. 3/7 (42.7%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Motivation (N = 6) | There is evidence supporting the view that chronic cannabis users demonstrate amotivation and reduced reward processing than non-users | (100–103) | Two case-control studies found that cannabis use is not associated with impairments in motivation | (104, 105) | There is a moderate level of evidence implicating a negative relationship between cannabis use and motivation. 4/6 (66.7%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Psychosocial Functioning (N = 8) | There is substantial evidence that daily or weekly cannabis use throughout high school is associated with lower educational and occupational attainment | (106–112) | One study indicated that cannabis use in high school is not associated with educational performance | (98) | There is a strong level of evidence implicating a negative relationship between cannabis use and psychosocial functioning. 7/8 (87.5%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Depression (N = 27) | There is evidence that daily or weekly cannabis use beginning in adolescence is a risk factor for a diagnosis of major depressive disorder (MDD) in adulthood | (54, 90, 100, 107, 109, 113–123) | Some evidence from case-control designs suggest that cannabis use is not associated with depression and acute administration of THC may decrease depressive symptoms for a short period of time | (51, 61, 124–132) | There is a mixed level of evidence implicating a relationship between cannabis use and increased depression. 16/27 (59.3%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Anxiety (N = 23) | There is evidence that chronic cannabis use beginning in adolescence and acute, high dose administration of THC is associated with an increase in anxiety symptomology | (13, 14, 41, 52–54, 90, 100, 107, 116, 119–121, 133) | However, there is also evidence that acute, low dosing of CBD is associated with a decrease in anxiety symptomology | (61, 113, 115, 122, 127, 129, 134–136) | There is a moderate level of evidence implicating a relationship between cannabis use and increased anxiety. 14/23 (60.9%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |
| Psychosis (N = 27) | There is substantial evidence that chronic cannabis use in adolescence and acute, high dose administration of THC is associated with an increased risk for a psychotic disorder or acute psychosis, respectively | (13–15, 24, 53, 54, 93, 107, 124, 132, 137–152) | There is minimal evidence that cannabis is not associated with greater psychotic symptoms | (61, 153) | There is a strong level of evidence implicating a relationship between cannabis use and increased risk for psychosis. 25/27 (92.6%) of included studies assessing this behavioral sequela observed a negative effect of cannabis use |