Teens and young adults whose parents use marijuana are at an increased risk of using weed, alcohol and tobacco, according to a study authored by a Harvard Medical School researcher.

Recent and past parental marijuana use poses a risk of substance use to their children, data from 24,900 parent-child pairs analyzed by National Surveys on Drug Use and Health from 2015-2018 showed.

Researchers examined the data and saw that parental marijuana use was a risk factor for marijuana and tobacco use by teens and young adults and for alcohol use by teens.

Marijuana use is increasing among adults, according to the study, and weed is often consumed with other substances like alcohol or tobacco.

Bertha Madras of Harvard Medical School authored the study published Friday in the Journal of the American Medical Association.

“Parental marijuana use conceivably poses a direct environmental risk of normalizing marijuana use and enabling access to marijuana for their offspring,” wrote Madras.

Among mothers living with teenage children, about 8% consumed weed in the past year and nearly 10% of fathers living with teens reported past-year pot use.

“In general, living with a parent who uses substances or has substance use disorder is a risk factor for use of substances among young offspring,” wrote Madras.

The findings mean that screening household members for substance use and counseling parents on the risks of smoking pot could help break the cycle of multi-generational substance use.

“Direct and indirect screening in medical settings of family members for marijuana use is an important and achievable goal,” wrote Madras.

Citing further research throughout the paper, Madras wrote that a positive screening result should trigger parent counseling on the risks posed by using drugs at home and educating them on modifying their substance use.

She said reducing substance use can be achieved through targeted strategies and prevention approaches that use mass media campaigns and community-based programs.

Madras cited other studies that indicate early exposure to weed also is associated with higher rates of addiction, impaired cognition, symptoms of psychosis, schizophrenia, depression, suicidal behavior and reduced educational achievement.