Differences in Cannabis Use across States and Age Groups

The Substance Abuse and Mental Health Services Administration (SAMHSA) provides information on the prevalence of cannabis used within the past year by state and age group (see Figure 1). This simple set of data provides some interesting insights into cannabis use patterns in the US.

Figure 1

For the US as a whole, the estimated prevalence of cannabis use in the past years is 21%. As expected there are large differences across age groups, but there is also a good amount of variation across states.

By Age Group

Let’s start with differences by age group.

Teen minors – 12 – 17 year olds – have the lowest prevalence of use, ranging from a high of 19% in New Mexico to a low of 7% in Utah, and with a 12% average prevalence across states. Interestingly, teen minors also have the smallest variation in use across states (see also Figure 2). Perhaps regional influences on behavior that cause differences in prevalence of cannabis use in older populations (18 – 25 and 25+) have not yet had enough time to take hold in 12 – 17 year olds. At the same time, the relatively constant 10% - 12% level of use in this age group across states suggests that there are underlying factors that exist at least across the nation that lead a nontrivial portion of teens to use psychoactive substances.

The youngest legal cohort – 18 – 25 year olds – has the highest prevalence of use, ranging from a high of 54% in Vermont to a low of 25% in Utah, and with a 39% average prevalence. Not only is prevalence highest for this age group, but it is also most variable across states. The high prevalence of use within this age range could reflect either or both of two factors. On one hand, 18 – 25 year olds are young adults of legal age. Traditionally, this group tends to be full of piss and vinegar, that is, they’re at an age when they’re most likely to seek out new experiences. Eventually, as young adults start to form families, they tend to settle down. So, then, the relatively high prevalence of cannabis use by 18 – 25 year olds could be due to their stage of life. At the same time, the 18 – 25 year old group has grown up in an environment in which cannabis has been increasingly legal and much more socially acceptable than that of older generations. In this sense, the higher prevalence of use by this group could reflect a permanently higher prevalence of use starting with younger generations, and continuing as they continue to age. I suspect that both factors are at play, in which case cannabis use by the current cohort of 18 – 25 year olds will attenuate a bit as the group ages, but it will still be higher than rates of use for the current 25+ population.

People who are 25 years old or older – the bulk of adult society – have a more moderate and more moderately variable prevalence of use, ranging from a high of 31% in Vermont to a low of 12% in Alabama, and with a 20% average prevalence. So the older population has about half the level of use as that of the young legal group.

Figure 2

Across Age Groups

The next thing to notice are the patterns of use across age groups. The prevalence of cannabis use across age groups tends to track well across states. That is, in states with higher adult population use of cannabis (25+), there is also higher use by both teen minors (12 – 17) and young legal adults (18 – 25) (see Figure 3), which suggests certain states have cultures more inclined towards cannabis use than other states:

Figure 3

If certain states are more inclined toward cannabis use than other states, then we would expect states with greater cannabis cultures to have legalized medical use earlier. And, indeed, that is what we see when we plot states’ prevalence of cannabis use by the adult population (18+) against the year states legalized medical cannabis use (see Figure 4):

Figure 4

Across Regions

Finally, if we compare the prevalence of cannabis use by region, we see that across age groups, cannabis use is slightly more prevalent in the West and slightly less prevalent in the South (see Figure 5). The larger differences in use across regions by 18 – 25 year olds is consistent with the larger variation across states for that age group seen in Figure 1. This suggests that the ways young adults choose to explore and experiment have nontrivial cultural influences. (SAMHSA data show that 18 – 25 year olds in the South report lower levels of use of alcohol, cannabis, and other drugs than young adults in other regions, but about the same level of use of tobacco.)

Figure 5

In Short

What we see, then, is that the prevalence of cannabis use tends to vary both (i) by age group, with higher levels of use by younger legal adults than older adults and (ii) by region, with higher levels of use in the West and lower levels of use in the South. At the same time, given the increasing social acceptance of cannabis, moving forward, we should expect to see greater levels of use by older adults, both due to new adoption by the current population of older adults, as well as by higher levels of use in younger populations as they age.