Medical marijuana's impact on overall cannabis use

In recent research commentaries I have referred to the political and social change regarding the acceptability and legalisation of cannabis in the US. This puts the US in a unique position to conduct research on the different sorts of impact from various regime changes, such as the impact on cannabis use frequency following the establishment of medical marijuana dispensaries. Freisthler and Gruenewald (2014) have just published an in-depth survey on precisely this topic. California allows cannabis use for recognised medical purposes, however; regulatory control of medicine dispensaries is set by local jurisdictions, which results in varying rates of access to dispensaries across Californian cities. This situation is valuable to research which adds to the growing but mixed data regarding the impact of differing laws (there have been noted increases in use in some states while other states have shown no such increase). It also adds to data describing medical marijuana users and recreational cannabis users (each are more likely to be male, Caucasian, around 40 years old, have lower income, have health insurance, be impulsive and tolerant of deviance, and live in areas of greater social disorder and neighbourhood disorganization, compared to non-users).

Freisthler and Gruenewald’s collected usable data from 8553 adults with a landline via a general population telephone survey conducted across 50 randomly selected cities in California (each separated by two unselected cities). This process resulted in large non-response rates (48%) but the authors corrected for this during analysis by using corresponding statistical weights. In addition, the authors noted the locations of medical marijuana dispensaries by roadside checking and internet listings. The telephone survey was lengthy and included information on participant demographics and socioeconomic status, community engagement, personality variables such as impulsivity and tolerance of deviance and aspects of cannabis use.

The average prevalence of recent cannabis use among participants was at 5.4% (ranging between 1.1% and 19.3% across cities), which was lower than the Australian population average of 10.1% (2010 National Drug Strategy Household Survey). The prevalence and frequency of use was higher among young (less than 30 years), single, white males with high incomes, high impulsivity and tolerance to deviance, especially when living among higher levels of social disorder. Notably, a total of 0.02 dispensaries or delivery services were present per average roadway mile (range: 0.00–0.07). Perhaps the most notable finding, however; was that even when controlling for participant personality, and demographic factors and community factors, the density of dispensary “shop fronts” (but not delivery services) was positively and significantly associated with cannabis use frequency.

What drives this important finding is left unanswered – it could just reflect supply and demand, numbers of doctors’ recommendations to use medicinal cannabis, or other growing operations. However, this study does highlight that introducing services which distribute medicinal cannabis will likely result in an increase of recreational and medicinal use in the surrounding area, particularly among young males. This may seem logical, however; we are in a time where these services are growing in numbers and are left uncontrolled from state or federal regulations. Caution must be urged when taking actions that increase any kind of cannabis use among our more vulnerable younger populations so as to avoid the substantial and still growing list of known negative life outcomes that this may cause.  

Freisthler, B. & Gruenewald, P.J. (2014). Examining the relationship between the physical availability of medical marijuana and marijuana use across fifty California cities. Drug and Alcohol Dependence 143, 244-250.