About one-quarter of individuals whose marijuana use is problematic in early adulthood have anxiety disorders in childhood and late adolescence, according to new data published in November 2017 in the Journal of the American Academy of Child & Adolescent Psychiatry. The study also shed light on an estimated 4% of adults who endured childhood maltreatment and peer bullying without resorting to chronic marijuana abuse, only to develop problems with the drug between the ages of 26 and 30.
“Given that more states may be moving towards legalization of cannabis for medicinal and recreational purposes, this study raises attention about what we anticipate will be the fastest growing demographic of users—adults,” says lead author Sherika Hill, PhD, an adjunct faculty associate in the Department of Psychiatry and Behavioral Sciences at Duke.
“A lot of current interventions and policies in the US are aimed at early adolescent users," she says. "We have to start thinking about how we are going to address problematic use that may arise in a growing population of older users.”
The findings are based on data from 1,229 participants in the Great Smoky Mountains Study, a long-term study of residents in 11 counties near the Appalachian Mountains in western North Carolina, where Hispanics and Latinos are underrepresented and Native Americans are overrepresented compared with the rest of the US.
The researchers defined problematic cannabis or marijuana use as daily consumption or a habit that meets diagnostic guidelines for addiction. They tracked participants’ patterns of use from the college years (ages 19-21) into adulthood (ages 26-30).
They found that more than three-fourths (76.3%) of participants didn’t use or develop a problem with marijuana during this period. The remaining quarter developed problems that researchers grouped into 3 profiles: those with limited problems, persistent problems, and delayed problems.
Limited problematic users (13%) had difficulty with marijuana either before age 16 or in their late teens and early 20s, but their habits dropped off as they aged. This group reported the highest levels of family conflict and instability during childhood, factors that are often associated with more drug use.
Persistent users (7%) had trouble with marijuana beginning as young as age 9, and their chronic use continued into their late 20s and early 30s. Large portions of this group had anxiety disorders in both childhood (27%) and between ages 19 and 21 (23%). They also had the highest rates of psychiatric disorders and involvement in the criminal justice system, and most said the majority of their friends were drug users, too. “This suggests that a focus on mental health and well-being could go a long way to prevent the most problematic use,” Hill says.
Delayed users (4%) comprised a small but unique group of individuals who did not have problematic marijuana use in adolescence or early adulthood but who became habitual users between ages 26 and 30. Blacks were 5 times more likely than whites to be in this group. More than one-half of delayed users were both bullied by peers and mistreated by caregivers as children; yet they also had lower rates of anxiety, alcohol use, and other hard drug use than persistent users.
“One of the important aspects of this study is that it has interviewed the same participants many times,” says E. Jane Costello, PhD, who has run the study since it began in 1993. “In particular, getting to know children well gives us the best chance of identifying persistent users early and intervening with them in good time.”