Despite this limitation, participants reported their pre-pandemic cannabis use so that we were able to control for retrospective use. The current research is also limited to the initial period of the pandemic. Since restrictions have been variously lifted and re-implemented in response to COVID-19 case counts, it is important to examine longer term effects of the pandemic on cannabis used and the role of demand using a longitudinal model. Furthermore, the sample size for the current study is modest for testing the hypothesized path model. However, our large R2 effect sizes suggest that we captured strong predictors of cannabis motives and problems during COVID-19 in our study. Next, since the MPT is a measure of hypothetical consumption of cannabis, actual cannabis consumption is not measured by this task. However, previous research has provided evidence for the validity of hypothetical purchase tasks for other substances . Future research is needed to support the validity of the MPT. Moreover, the MPT instructional set refers to smoking “hits” of grow cannabis, which may impact its use among those whose primary form of cannabis use is vaping or consuming edibles.

Though the majority of the sample in the current study indicated that dried cannabis was their primary form of use, this presents a clear limitation to the ecological validity of the MPT. Recent qualitative research on the MPT has recommended against the use of the term “hits” in favor of “grams” and that the specific mode of cannabis administration be incorporated into future iterations of the MPT . A further potential limitation is that the study measures were administered online rather than in a laboratory context. This presents several drawbacks when administering the MPT, namely that the research team was not able to emphasize important parts of the instructions or answer questions; it is possible that participants’ performance was impacted in a negative way by these factors . Also, because our sample was drawn from a larger sample of Canadian drinkers it is possible that cannabis use motives in our sample may have differed systematically from those of cannabis-only users. Co-use of cannabis and alcohol is associated with elevated alcohol demand , so it is possible that co-use may also systematically impact both cannabis demand and motives for use.

Finally, we acknowledge that our sample had a rather high level of income . While household income was unrelated to cannabis use variables in this study, our findings may not generalize to samples with lower income. In conclusion, this study replicates a modest body of previous research linking indoor cannabis grow system demand to cannabis-related problems and provides evidence for the role of coping motives in the increased cannabis-related problems experienced by those with elevated cannabis demand. Further research is needed to replicate this research within a sample of cannabis-only users and in a real-world, offline setting.Substance use disorders  are a major public health issue in the United States ; in 2019, more than 2.5 million Americans died due to drug- or alcohol-related causes . Many adults who develop SUDs report initiating substance use during adolescence . Three substances — alcohol, tobacco, and cannabis — have particularly widespread use among adolescents . Polysubstance use, or the consumption of more than one substance simultaneously, is also common during the developmental period of adolescence. For example, 34% of adolescents reported using two or more substances from among alcohol, cigarettes, and cannabis prior to age 16 . In another study, 41.9% of adolescents  reported alcohol and marijuana co-use .

Several factors have been identified to be associated with increased risk of substance use and its severity among adolescents such as lower levels of parental monitoring, higher levels of parental substance use, family history of substance use, and lower levels of parental education . Initiating substance use at a younger age also contributes to more severe use later in life . Several studies have also explored risk factors that lead to co-use of substances by adolescents including individual, familial, and socio-demographic factors . Given the potential short- and long-term harms associated with hazardous substance use in adolescence, it is imperative to identify adolescents at high risk of developing hazardous substance use. Hazardous substance use is use of substances that increases the future risk or likelihood of health consequences; this does not include use that has already led to health consequences . A few tools are available for individual substance risk prediction. In particular, Hayatbakhsh et al.  developed a risk score for cannabis use and disorder in early adulthood based on early life risk factors.