Mental Health Blog

Adolescent Cannabis Use and Harm Reduction

• February 26, 2025
• The REACH Institute

“We know that 10% of adult cannabis users will develop a substance use disorder or addiction. That number is double in adolescents,” explains child and adolescent psychiatrist Blair Ritchie, MD FRCPC, when describing one of the many research-documented risks of youth cannabis use. 

Yet with decriminalization and legalization in many states, cannabis is increasingly seen as socially acceptable and low risk. In the U.S., 40% of adolescents under 18 report having used cannabis, and initiation of cannabis use is especially high in middle schoolers (ages 11-13). 

The conflicting social and health dynamics can leave clinicians and parents uncertain of the risks and appropriate responses. To clarify the issue, Dr. Ritchie walks us through how to talk to pediatric patients and parents about cannabis through a harm-reduction framework. 

Talking to Adolescents About Cannabis Use

Dr. Ritchie advises clinicians to discuss substance use annually with all patients age 10 or older. This can be done in multiple ways. Evidence-based tools like the CRAFFT teen health screen assess both substance use and related risks (such as riding in a vehicle with someone who has used drugs or alcohol). The CRAFFT can be administered in writing, online, or verbally. 

More informal screening conversations when the parents are not in the room can also be effective, such as asking adolescents, “What substances have you tried? Have you tried cannabis? How about alcohol?”

Regardless of the screening format, to build trust Dr. Ritchie advises clinicians to be transparent and upfront with both youth and parents about confidentiality and privacy. Clinicians should clarify what will be shared with parents, what will be kept confidential, and under what circumstances that might change.

The Essentials of a Harm Reduction Approach for Cannabis Use

“There are significant risks to using cannabis that are unique to being a youth,” explains Dr. Ritichie. “As a clinician, you want to share the risks. But the best approach for changing behavior is to help adolescents and youth come to the decision themselves.” 

Dr. Ritchie advises a three-part harm reduction approach: 

• Neutral education about the risks of cannabis use. 
• Motivational interviewing to help patients choose to reduce cannabis use and, ideally, abstain. 
• Introduction of strategies to reduce the risk of harm caused by cannabis use.

Neutral Education on the Risks of Youth Cannabis Use

Despite a societal perception of low risks, there is a growing body of research on the harms of cannabis use among youth. Clinicians should share the facts with adolescents in a neutral way, advises Dr. Ritchie. “Fear-mongering does not help.” 

• Psychosis: Multiple studies show that youth cannabis users are two to four times more likely to experience psychosis, with the risk increasing with the dose. 

• Reduced IQ: Research based on the New Zealand Dunedin database has identified a permanent drop in IQ among frequent cannabis users under age 18. 

• Substance Use Disorder: Among young people who use cannabis regularly, meta-analysis shows that up to 33% may develop a substance use disorder.

• Motor Vehicle Accidents: Cannabis can impair executive function for up to 24 hours. Many studies have shown that driving after using cannabis significantly increases the risk of fatal and non-fatal injuries in motor vehicle accidents. At this time, there is no known “safe” level of cannabis consumption while driving. 

• Lung Health: Current research on the effect of smoked or vaped cannabis on lung health and cardiovascular health is limited, but there is the potential for harm.

• Rising THC Levels: Parents especially should know that cannabis today is very different from what they may be familiar with. Over the last three decades, the percentage of the psychoactive compound THC in cannabis has increased from less than 2% before the 1990s to up to 28% today. Edibles and vapes can have even higher THC percentages—up to 95%. This makes it easy to unknowingly consume very high amounts of THC, which only increases overall risk. 

Dr. Ritchie also reports that many parents ask about using CBD oil to treat anxiety and other disorders. To date, research shows that CBD can benefit some children with refractory epilepsy. However, Dr. Ritchie cautions that the CBD market is not closely regulated and there is little research demonstrating the efficacy of CBD for youth beyond refractory epilepsy. 

Motivational Interviewing to Reduce Cannabis Use

“With motivational interviewing, a clinician’s role is to help adolescents find reasons to quit or reduce their use of cannabis,” explains Dr. Ritchie. “For some patients, it’s their sport that makes them want to quit. For some it’s money. For some, it’s conflict in the family or conflict with friends.”

Once clinicians have shared information about the risks of youth cannabis use, they should ask the adolescent questions like: 

• What do you think of the information I just shared? 
• What are the pros and cons of cannabis use for you? 
• What would you like to change about your cannabis use? 

If the patient is ready to reduce or stop their cannabis use, clinicians can guide them in setting goals and creating plans to meet those goals. 

To learn more about motivational interviewing, Dr. Ritchie recommends clinicians take advantage of the wealth of resources offered by SBIRT Oregon, which includes guides for motivational interviewing with adolescents and video demonstrations. 

Harm Reduction Strategies for Adolescents Who Use Cannabis

While the ideal outcome is that adolescents choose to abstain from cannabis, reducing immediate and long-term harm should still be a priority. 

There are several research-backed harm reduction strategies specifically for cannabis use. For example, research supports delaying the age of initial cannabis use, reducing the frequency of use, choosing cannabis products with lower THC, and not driving after consuming cannabis products (or getting in a car with someone who has consumed cannabis). 

RESOURCES: 

• View the CRAFFT teen health screen for assessing substance use and related risks.
• To learn more about a practical approach to harm reduction for substance use, Dr. Rithchie recommends the wealth of resources at SBIRT Oregon. 
• When counseling adolescents who use cannabis, Dr. Ritchie recommends this printable two-page handout that details what lower-risk cannabis use looks like.