In the US state of Colorado, use and sale of cannabis for recreational purposes has been legal since January 2014, and it has been commercialised for medical purposes since 2009. The main arguments for legalisation were that it would increase law enforcement efficiency, revenue and individual freedom.
The state government instructed the state Department of Public Safety to report on key statistics of cannabis-related topics including crime, impaired driving, hospital visits, usage rates, effects on youth. A second biennial report was released in October 2018. The main findings are as follows:
The number of serious crimes of illegal production and sale of cannabis fell considerably between 2008 and 2014, when they started to rise again. Cannabis-related organised crime cases varied over the period 2008 to 2013 but significantly increased between 2014 and 2017.
The number of plants seized in Colorado by the DEA has varied since 2008, from 5 000 to 40 000 plants per year. Other seizures of plants grown on public lands have also fluctuated, but they steadily increased since 2014; in 2017, the National Forest Service seized over 70 000 plants.
Diversion out of state
The number and weight of cannabis products seized by the US postal service has increased every year since 2010. The number of seizures of Colorado-sourced herbal cannabis in other states peaked in 2015 and declined since, but increasingly more concentrates and edibles are being found.
The percentage of arrests for cannabis-only impairment by the Colorado State Patrol has remained at 6-8 % since 2014. The share of drivers involved in fatal crashes who tested positive for any cannabinoid has increased from 11 % to 21 % over the last 4 years, but the percentage that tested positive above the state-defined level of impairment of 5 ng/ml blood-THC fell from 11.6 % in 2016 to 7.5 % in 2017 (recording blood-THC levels started only in 2016).
Cannabis-related hospitalisations have increased steadily since 2000. Calls to poison centres have levelled off since 2014, when stricter regulation and prevention measures were introduced to control edible products.
School year 2016/17 was the first in which cannabis-related expulsions or law enforcement interventions were recorded separately, and it showed that cannabis was the single biggest reason for expulsions and interventions. Nevertheless, since school year 2009/10, the graduation rate has risen and the drop-out rate has fallen.
Young cannabis users
The National Survey on Drug Use and Health (NSDUH) questions about 500 young people in the state to compare with other states, and the Healthy Kids Colorado Survey (HKCS) now questions nearly 50 000 students.
The rate of last-month cannabis use among 12- to 17-year-olds reported via NSDUH for the 2015/16 school year (9.1 %) was the lowest it has been since 2007/08.
According to HKCS, the proportion of high school students reporting trying cannabis (lifetime use) or reporting past 30-day use did not vary to a statistically significant degree from 2005 to 2017.
Cannabis taxes make up about 1.52 % of all tax revenue collected in the state.