Quantity and frequency of cannabis use in relation to cannabis-use disorder and cannabis-related problems.

BACKGROUND:In almost all of the literature examining the relation between cannabis use and cannabis-related harms, researchers have neglected to include quantity measures of cannabis use. The study aims to assess whether cannabis: (1) quantity predicts harms; and (2) quantity might interact with other key variables (age, gender, and frequency of use) vis-à-vis the outcomes. METHOD:Using the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions-III (NESARC-III), the current study (n = 36,309; n = 3,339 past-year cannabis users) employed a logistic-regression approach to assess the cross-sectional relations between the continuous variables of cannabis-use quantity and frequency and two Alcohol Use Disorder and Associated Disabilities Interview Schedule-5 (AUDADIS-5) DSM-5-based outcomes: past-year cannabis-use disorder (CUD) and past-year cannabis-related problems (CRP). RESULTS:In the CUD model, the key variables log quantity [OR = 1.98 (95 % CI, 1.64;2.39), p < 0.001], log frequency [OR = 1.78 (95 % CI, 1.62;1.96), p < 0.001] and the log-quantity-by-log-frequency interaction [OR = 0.83 (95 % CI, 0.75;0.93), p = 0.002] were statistically significant. The final CRP model included the following main predictors: log quantity [OR = 2.13 (95 % CI, 1.70;2.66), p = <0.001], log frequency [OR = 1.50 (95 % CI, 1.36;1.65), p = <0.001], and a log-quantity-by-log-frequency interaction [OR = 0.82 (95 % CI, 0.73;0.93), p = 0.002]. CONCLUSIONS:The quantity-by-frequency interactions in both models showed that the relative effect of quantity on cannabis-use disorders and cannabis-related problems decreased as frequency increased, and vice versa.