The Association between Legal Recreational Cannabis Access and Over-the-Counter Sleep Aid Sales in Colorado

Conventional over-the-counter (OTC) sleep aids are of limited effectiveness, while the use of cannabis for treating insomnia has been increasing, according to survey studies. We examined the relationship between the legalization of recreational cannabis in Colorado and OTC sleep aid sales. Grocery store scanner data and a difference-in-differences fixed effects panel regression design were used to compare the change in the monthly market share of sleep aids before and after dispensary-based recreational cannabis access in Colorado counties. County-level access to recreational cannabis dispensaries was measured using dispensary existence, sales, and count in Colorado’s 64 counties between 12/2013 and 12/2014, with the first dispensaries opening in 19 counties on 1/1/2014 and a total of 292 dispensaries operating in 32 counties and generating almost $3.3M in sales by 12/2014.

Annually differenced market shares for sleep aids, total OTC sleep aids unit sales over total OTC medication unit sales sold in a store, were used to account for store-level demand shifts in OTC medication markets and seasonality. Monthly change in a store’s sleep aid market share, relative to one year prior, was compared before and after a recreational dispensary opened in the store’s county. We analyzed 587 stores selling sleep aids in 64 Colorado counties between 12/2013 and 12/2014. Relative to the OTC medication market, sleep aid market shares were growing prior to the availability of recreational cannabis. The trend reversed (a 236% decrease) with entry of the first dispensary (-0.33 percentage points, p<0.01) from a mean market share growth of 0.14 (SD=0.97, measured from 0 to 100), and market shares continued to decline when more dispensaries entered the county (-0.01 percentage points per new dispensary, p<0.01) and with higher county-level recreational cannabis sales. The negative associations were driven by reductions in diphenhydramine- and doxylamine-based sleep aids rather than herbal sleep aids and melatonin.

The statistically, economically, and clinically significant negative association between legal recreational cannabis access and OTC sleep aids sales potentially demonstrates a revealed consumer preference for recreational cannabis over conventional OTC sleep aids with implications for the approximately 50% of the U.S. population who experience sleep disturbances. Patient-level studies should be conducted to evaluate the risks and benefits of cannabis relative to OTC sleep aids, especially tradeoffs between the apparent effectiveness of cannabis and its addictive potential.