Marijuana Admissions to Substance Abuse Treatment Aged 18 to 30: Early vs. Adult Initiation

Research increasingly confirms that marijuana use is harmful. Acute symptoms of marijuana intoxication include impaired short-term memory, attention, judgment, and cognitive function, as well as increased heart rate.¹ Symptoms that can persist for weeks after the immediate effects of marijuana have worn off include insomnia and, possibly, impaired memory and learning.² When continued over years, a pattern of heavy, daily, or almost daily use can increase some health risks, including marijuana dependence, chronic cough or respiratory impairment, cardiovascular disease, and adverse effects on psychosocial development and mental health.^2,3

The long-term effects of marijuana use on adults who initiated use as adolescents are especially striking. If marijuana use begins in adolescence when the brain is still developing, the negative impact of chronic marijuana use on cognitive function and structure can last several years and may be permanent.^3,4 For example, one study of marijuana users who began using in adolescence revealed deficits in the areas of the brain responsible for learning and memory,⁵ which can, in turn, impact an adolescent's ability to successfully function in the contexts of school, work, and family.^1,3 Another study showed that among persistent adult marijuana users, those who started using marijuana in their youth lost as many as 8 IQ (intelligence quotient) points between the ages of 13 and 39. These lost cognitive abilities were not restored in those who quit using marijuana as adults.³ In contrast, among the study's sample of persistent marijuana users who initiated use as adults, the same cognitive declines were not detected.³ Moreover, the risk for youth becoming dependent on marijuana is acute: it has been estimated that 9 percent of all marijuana users become dependent—this proportion increases to 17 percent among young initiates.³ Thus, age of marijuana initiation can impact marijuana dependency which in turn can have a bearing on overall health and future treatment needs.

The Treatment Episode Data Set (TEDS), a national data system of annual admissions to substance abuse treatment facilities, can be used to identify differences between treatment admissions involving persons who started using marijuana at age 17 or younger and those that initiated as adults. TEDS collects data on the primary substance of abuse and up to two additional substances of abuse at the time of admission to substance abuse treatment. This report considers substance abuse treatment admissions that reported marijuana as one of the three substances of abuse at treatment entry, comparing those that initiated marijuana use before the age of 18 ("marijuana admissions reporting early initiation" or "early initiates") with those that reported initiating use at age 18 or older ("marijuana admissions reporting adult initiation" or "adult initiates"). Both groups were restricted to those marijuana admissions that were aged 18 to 30 at treatment entry. Comparisons between the two initiation groups use 2010 data unless otherwise noted.

TEDS is a census of all admissions to treatment facilities reported to the Substance Abuse and Mental Health Services Administration (SAMHSA) by State substance abuse agencies. Because TEDS involves actual counts rather than estimates, statistical significance and confidence intervals are not applicable. The differences mentioned in the text of this report have Cohen's h effect size ≥ 0.20, indicating that they are considered to be meaningful.

According to TEDS, in 2010 there were 687,531 substance abuse treatment admissions aged 18 to 30. Of these, 340,212 reported marijuana abuse at treatment intake and the age of marijuana initiation. The majority of marijuana admissions reported early initiation (started using marijuana at age 17 or younger; 86.8 percent); the remaining 13.2 percent reported adult initiation (started using marijuana at age 18 or older). These proportions remained relatively constant between 2000 and 2010 (Figure 1).

Marijuana admissions aged 18 to 30 were primarily male and non-Hispanic White (Table 1). These characteristics were most marked among the early initiates, where 70.2 percent were male and 62.2 percent were non-Hispanic White. Among admissions reporting adult marijuana initiation, 64.4 percent were male and 54.3 percent were non-Hispanic White. Notably, among admissions reporting adult marijuana initiation, 28.3 percent were non-Hispanic Black compared with 19.7 percent of those reporting early initiation.

Marijuana admissions reporting early initiation were younger than those reporting adult initiation. Among those reporting early initiation of marijuana use, 60.2 percent were aged 18 to 24, while 47.9 percent of adult initiates were aged 18 to 24 at the time of admission. Due to the relative youth of the majority of marijuana admissions, educational attainment was assessed by considering admissions that were at least 21 years of age. Over 6 in 10 early initiates (62.0 percent) and about 7 in 10 adult initiates (70.6 percent) aged 21 to 30 had completed high school.

Overall, the proportion of admissions reporting marijuana as a substance of abuse among admissions aged 18 to 30 remained relatively constant between 2000 (48.6 percent) and 2010 (49.9 percent). Moreover, the average age at the time of treatment admission of early initiates and adult initiates has also remained constant over time. Early initiates were about 23 years of age, on average, at treatment admission in both 2000 (23.1 years) and 2010 (23.5 years). Adult initiates were about 25 years of age on average at treatment entry in both of those years (24.8 in 2000 and 24.7 in 2010).

In 2010, the majority of marijuana admissions aged 18 to 30 that reported early marijuana initiation began using marijuana between the ages of 12 and 17 (87.9 percent), and the remainder (12.1 percent) began using at age 11 or younger. Among adult initiates, 95.9 percent reported initiating marijuana use between the ages of 18 and 24.

Because early initiates began using marijuana at a younger age than adult initiates, it is expected that early initiates would report longer durations of marijuana use. The average duration of marijuana use was 9.7 years among early initiates and 5.4 years among adult initiates. A higher proportion of early initiates than adult initiates reported 6 or more years of marijuana use (81.1 vs. 45.8 percent) (Figure 2).

Both initiation groups were similar in terms of the proportions reporting marijuana as the primary substance of abuse. Specifically, 47.9 percent of admissions that reported early marijuana initiation and 50.6 percent of admissions that reported adult initiation identified marijuana as their primary substance of abuse.

Early initiates of marijuana reported abusing more substances than adult initiates. Keeping in mind that TEDS allows for recording of up to three substances of abuse for each admission, early initiates abused an average of 2.2 substances compared with an average of 2.0 substances for adult initiates. Early initiates were more likely to abuse three substances than adult initiates (35.8 vs. 22.9 percent; Figure 3). Early marijuana initiates reported heroin abuse at about twice the rate of adult initiates (11.1 percent vs. 5.5 percent; data not shown). The proportions reporting the abuse of other drugs, including alcohol, cocaine, and methamphetamine, were similar between early and adult initiates (data not shown).

Marijuana admissions reporting early initiation reported more extensive substance abuse treatment histories than their peers. Specifically, early initiates were more likely to report at least one prior admission to treatment compared with adult initiates (56.5 vs. 40.5 percent) (Figure 4).

The two marijuana initiation groups were similar with regard to mental health status and living arrangement.⁶ About one quarter of all initiates reported a co-occurring mental health problem (28.9 percent of early initiates and 24.4 percent of adult initiates). Similar proportions of both groups reported being homeless (7.6 percent among early initiation group and 6.2 percent among adult initiation group).

The picture that emerges of marijuana admissions reporting early initiation shows a complicated drug use history characterized by longer durations of marijuana use, the abuse of more substances, and more reported prior treatment episodes compared with marijuana admissions reporting adult initiation (Table 2). Treatment of individuals whose marijuana use began during adolescence may be complicated by the potential for sustained, and possibly permanent, cognitive problems because of their early age at initiation and long period of use.^2,3,4,5,6 Thus, admissions that initiate marijuana use early may require more intensive services to address polysubstance use, including targeted relapse prevention and aftercare in order to build the skills necessary for stabilization and sustained recovery.

The high proportion of marijuana treatment admissions whose marijuana use began at age 17 or younger remained relatively constant from 2000 to 2010. The persistence of this proportion points to the need for effective prevention services targeted at teens. Moreover, the report findings show that over one tenth of marijuana admissions reporting early initiation began using at age 11 or younger, which signals the critical importance of including youth under the age of 12 when designing and implementing youth-focused prevention efforts. Such efforts may derive increased benefit if they address marijuana prevention and target males specifically.

TEDS_122