As a guinea pig for adult-use cannabis legalization, Colorado is often a target for prohibitionists trying to magnify what they consider shortcomings of the first state-legal market.

Two key arguments repeated by lawmakers voting against reform efforts include their concerns about how legalization might impact youth as well as the possible increase of impaired drivers on their state roadways.

In Minnesota, where House members discussed an adult-use bill for roughly five hours in May, before it passed via a 72-61 vote, Republican Rep. Glenn Gruenhagen took aim at Colorado in his efforts to deter passage of House File 600. While H.F. 600 did clear the House, it did not make its way through the Senate.

“Since recreational marijuana was legalized [in Colorado], traffic deaths in drivers which tested positive for marijuana increased 135 percent while all other traffic deaths increased 24 percent,” he said. “So, one of the members said, ‘This doesn’t cause death.’ Well, it does with increased traffic death.”

Gruenhagen went on and said, “One other finding is that marijuana use ages 12 and older increased 30% and is 76% higher than the national average, currently ranking third in the nation in Colorado.”

Lawmakers who oppose adult-use legalization in other states that have debated or passed bills this year have echoed similar reservations before casting their no votes.

While the representative from Minnesota declared to have non-partisan studies on his side, his claims have since been debunked (youth impacts) or gone unsubstantiated (traffic safety) by Colorado’s most recent biennial “Impacts of Marijuana Legalization” report, which was released this July and commissioned by the state’s Division of Criminal Justice.

After Colorado voters passed a ballot measure to fully legalize cannabis in the 2012 general election, possession and cultivation became legal on Dec. 10, 2012, when Gov. John Hickenlooper issued an executive action adding Amendment 64 to the state constitution. The commercial sale of cannabis to the general public under an established licensing system did not begin until Jan. 1, 2014. 

Before adult-use legalization, Coloradans legalized medical cannabis through a 2000 ballot measure. Data going back to 2005 is included in the commissioned report on the impacts of legalization, which was mandated by the Colorado General Assembly in 2013. 

The executive summary of this year’s report states: “The majority of the data sources vary considerably in terms of what exists historically, and the reliability of some sources has improved over time. Consequently, it is difficult to draw conclusions about the potential effects of marijuana legalization and commercialization on public safety, public health, or youth outcomes, and this may always be the case due to the lack of historical data.

“Furthermore, the measurement of available data elements can be affected by [the] very context of marijuana legalization. For example, the decreasing social stigma regarding marijuana use could lead individuals to be more likely to report use on surveys and also to health workers in emergency departments and poison control centers, making marijuana use appear to increase when perhaps it has not.”

Impact on Youth

According to the most recent report, the proportion of Colorado high school students reporting using cannabis ever in their lifetime remained statistically stagnant from 36.9% in 2013 to 35.9% in 2019. In addition, Colorado’s 2019 rate of 35.9% was slightly lower than the national rate of 36.8% of high school students reporting using cannabis ever in their lifetime.

For high school students who reported using cannabis in the past 30 days, Colorado’s 20.6% rate was slightly lower than the nation’s 21.7% rate in 2019. Neither the Colorado rate of use nor the national rate experienced significant changes from 2013 to 2019, according to the report.

“There was no statistically significant difference between Colorado student responses compared to national data,” the report stated. “The percentage of high school students reporting past 30-day use also remained stable, with no significant changes between 2005 and 2019.”

The data was gathered through the Healthy Kids Colorado Survey, which the Colorado Department of Public Health and Environment began administering to high school students in 2005, and to middle school students in 2013. The sample information included 46,537 high school students and 6,983 middle school students in 2019.

Meanwhile, the National Survey on Drug Use and Health is administered annually to those aged 12 and older by the federal Substance Abuse and Mental Health Services Administration, which the Colorado report uses to derive its comparisons.  

“The proportion of students trying marijuana before the age of 13 went down significantly in Colorado, from 9.2% in 2015 to 6.7% in 2019,” the Colorado report stated. “These findings were not statistically different from the national data.”

The report added that the trend of past 30-day cannabis use among high schoolers and middle schoolers showed “no significant changes occurred within any grade level [from sixth through 12th grade] between 2013 and 2019.”

Following are other highlights regarding youth impacts in the report:

• In 2019, the prevalence of past 30-day cannabis use was significantly higher among Hispanic (23.2%), American Indian/Alaskan Native (26.7%), Native Hawaiian/Pacific Islander (29.4%), and multiple races (24.8%) compared to white (19.4%) and Asian (9.7%) high school students.
• In 2019, past 30-day cannabis use rates increased by grade level, with 12th graders (26.9%) twice as likely to report using cannabis than ninth graders (13.3%)
• Among those who use cannabis, the percent of high school students reporting dabbing cannabis in the past 30 days increased significantly from 2017 (20.3%) to 2019 (52.0%). In contrast, the percent reporting smoking cannabis decreased significantly from 2017 (88.4%) to 2019 (77.9%).
• High school students’ perception of cannabis posing a moderate/great risk if used regularly decreased from 2011 (57.6%) to 2019 (50.1%)
• High school students’ perception of easy access to cannabis decreased: 57.2% of students reported that it would be sort of/very easy to get cannabis in 2011, while 51.4% of students reported it would be sort of/very easy to get cannabis in 2019. 

Traffic Safety

The scope of driving under the influence of cannabis is difficult to gauge for several reasons, according to the report:

1. There is no criminal charge that specifies that the driver is impaired by drugs instead of, or in combination with, alcohol. The current statute applies to driving under the influence of alcohol, drugs or a combination of the two.
2. There is no central repository of toxicology results that would allow for an analysis of trends.
3. At a traffic stop, law enforcement may choose not to pursue additional toxicology testing if the driver is exhibiting indications of impairment from alcohol. The additional time and cost required for further toxicology testing may not be considered worthwhile if the burden of proof for impairment is already being met by a blood-alcohol content (BAC) level.
4. After an arrest, if the officer has probable cause to believe the suspect is impaired by drugs and/or alcohol, the officer may transfer the suspect to a location where blood can be drawn for further toxicology screening. The delta-9 tetrahydrocannabinol (THC) level in blood decreases rapidly in the first hour after use, then gradually thereafter, making prompt testing critical.
5. Furthermore, high THC blood concentration does not perfectly correspond to impairment. Chronic cannabis users had measurable concentrations of delta-9 during a seven-day abstinence period. The highest level observed at the conclusion of the seven days was 3.0 nanograms per milliliter (the “permissible inference” driving limit is 5.0 ng/mL), as a result of THC being stored in fat and its ability to slowly release from the tissue. This becomes a problem for frequent and medicinal users who may continuously have THC detectable in their blood without noticeable impairing effects.

Also making it difficult to gauge the impact of cannabis legalization on traffic safety is “the increase in law enforcement officers who are trained in recognizing drug use—from 129 officers in 2012 to 221 in 2020—which can increase drug detection rates apart from any changes in driver behavior,” the report stated.

Going back to Minnesota Rep. Gruenhagen’s claim about Colorado experiencing increased traffic deaths among drivers who tested positive for THC since legalization, here is what the report found: the number of fatalities for drivers who tested positive for cannabinoids, or cannabinoids in combination of alcohol and/or other drugs, increased by 140%, from 55 in 2013 to 132 in 2019.

However, the report noted that the detection of any cannabinoid in one’s blood is not an indicator of impairment, but only indicates presence in one’s system. In Colorado traffic fatalities where at least one driver was drug tested, the percentage of those testing above the 5.0 ng/mL permissible inference level remained statistically unchanged from 2016 (14%) to 2019 (13%).

In a broader study of impaired drivers, the number of cases where drivers were screened for cannabinoids increased from 3,946 in 2016 to 5,032 in 2018; however, the percentage of those drivers testing positive for cannabinoids decreased from 73.1% to 66.3%. Those who tested at or above the 5.0 ng/mL limit rose slightly, from 47.5% to 49.6%, while the median level decreased from 5.9 ng/mL to 5.2 ng/mL from 2016 to 2018.

“The lack of comparable federal data across many metrics makes it difficult to compare changes in Colorado to other jurisdictions which may have not legalized marijuana,” the report stated. “In sum, then, the lack of pre-commercialization data, the decreasing social stigma, and challenges to law enforcement combine to make it difficult to translate these preliminary findings into definitive statements of outcomes.”

Public Safety

The total number of cannabis arrests have plummeted since legalization, dropping 68% from 2012 (13,225) to 2019 (4,290). Possession arrests, which make up the majority of all cannabis arrests, decreased by 71%, while sales arrests decreased by 56% and production arrests increased by 3%.

The overall steep decline included all races and ethnicities, but not at equal rates: cannabis arrests decreased by 72% among white individuals, 55% for Hispanics and 63% for Black Coloradans.

Moreover, the cannabis arrest rate for Blacks (160 per 100,000) was more than double that of white individuals (76 per 100,000) in 2019. “This disparity has not changed in any meaningful way since legalization,” the report stated.

Meanwhile, court filings related to cannabis declined 55% between 2012 (9,925) and 2019 (4,489). Filings fell by 67% for adults 21 or older.

And the number of cannabis plants seized on public lands—one indicator of an illicit market—has fluctuated significantly, from 46,662 seized plants in 2012, to a high of 80,826 plants in 2017, and down to a low of 1,502 plants in 2018.

General Health

The number of adults reporting cannabis use in the past 30 days increased significantly from 2014 (13.4%) to 2019 (19%), according to the report.

Following are some of the highlighted statistics regarding adult use:

• Males have significantly higher past 30-day use (22.9%) than females (15.1%).
• Adults 26-34 years old reported the highest past 30-day usage rates (29.4%), followed by 18-25-year-olds (28.8%), 35-64-year-olds (17.3%) and those 65 years and older (9.3%).
• The cannabis usage rates of those 65 and older has more than tripled since 2014.
• Those reporting smoking cannabis flower decreased from 87.2% of users in 2016 to 76.1% in 2019. This compares to increases in eating/drinking (35.2% in 2016 to 43% in 2019), vaping (22.9% in 2016 to 32% in 2019), and dabbing (16.8% in 2016 to 19.6% in 2019).

The number of calls to poison control centers mentioning human cannabis exposure increased over the past decade—from 41 calls in 2006 to 276 calls in 2019.

The overall rate of treatment admissions for those reporting cannabis as their primary substance of use decreased from 222 admissions per 100,000 population in 2012 to 182 admissions per 100,000 in 2019.

For youth aged 10 to 17 years old who were admitted for treatment for substance use in 2019, 73.5% reported cannabis as their primary substance of use. That rate has increased fairly steadily from 61.6% in 2008.