By Linda Carroll

(Reuters Health) – Teens and young adults have a higher likelihood of taking up marijuana if their parents use the drug, a new study suggests.

From a survey of nearly 25,000 parent-child pairs, researchers found that parental marijuana use was associated with an increased risk that adolescents and young adults who live at home will start using the drug, according to a report in JAMA Network Open.

For parents who currently use cannabis or who have used the drug in the past, convincing kids not to take up the drug can be more complicated than for parents who never tried marijuana, said the study’s lead author, Bertha Madras, a professor of psychobiology at the Harvard Medical School and the McLean Hospital.

Parents’ use of marijuana “normalizes” it for the kids, Madras said. So parents need to explain why it’s OK for the parent to use it but not the kids.

“The most important thing to tell kids is to stay away from drugs while their young, developing brains are at risk,” Madras said, adding that research has shown marijuana use in teens can derail normal brain development.

Marijuana has also been shown to affect kids’ academic performance, Madras said. “It interferes with learning and memory,” she explained. “If a child uses it before school or even a day before their ability to learn in the classroom is much reduced.”

Another issue is the likelihood of addiction, Madras said. The rates of addiction are double if marijuana use starts in adolescence rather than adulthood, she said. “After four years, 20% will have marijuana use disorder,” she added. While that means 80% do not develop an addiction to cannabis, “no one can predict who will and who will not get into trouble with a drug,” Madras said.

Madras and her colleagues analyzed data from the 2015 through 2018 National Surveys on Drug Use and Health (NSDUH), which are conducted by the Substance Abuse and Mental Health Services Administration (SAMSHA).

The researchers focused on adolescents and young adults who had a parent born between 1955 and 1984 who also took part in the survey. The NSDUH collected data on lifetime and past year use – and misuse – of tobacco, alcohol, and drugs such as marijuana, cocaine, heroin and methamphetamines.

After accounting for factors such as peer use of drugs, urban versus rural homes, parental attitudes towards smoking and drinking, gender, family income and parental mental health, the researchers found that kids with moms who had used marijuana in the past, but not for at least a year, were 30% more likely to take up marijuana compared to kids with mothers who never used the drug.

Compared with kids whose moms never used marijuana, those whose mothers used the drug within the past year, but fewer than 52 times, were 70% more likely to have started using cannabis. Similarly, kids with dads who used marijuana within the past year, but fewer than 52 times, were 80% more likely to take up cannabis compared to kids whose parents never used the drug.

Similar results were found with young adults.

One thing the study can’t disentangle is the effects of genetics versus the impact of environmental factors, said Dr. Michael Lynch, medical director of the Pittsburgh Poison Center at UPMC.

That said, the findings underscore the need for parents who use marijuana to “think about the impact this could have on their children,” Lynch added.

Parents who have used the drug can have frank talks with their kids, Lynch said. Those who quit can “talk about why they stopped and what they perceived about it that was not good,” he added.

Those who are currently using cannabis might consider quitting, “since actions speak louder than words,” Lynch said. Parents who don’t want to quit “need to have a discussion about the difference between adults and adolescent use,” he added.

SOURCE: JAMA Network Open, online November 22, 2019.