Teens with ADHD

Q: “What Should My Teen Know About Marijuana and ADHD?”

“Smoking marijuana at a young age may also carry serious long-term implications, like executive dysfunction and permanent changes in brain function.”

Timothy Wilens, M.D.
By Timothy Wilens, M.D. Verified Updated on May 8, 2023
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Close-up of Lighting Up a Marijuana Joint.
Close-up of Lighting Up a Marijuana Joint.

Q : “My teen, who has attention deficit hyperactivity disorder (ADHD), uses marijuana. Is it harmful? Would marijuana use affect the efficacy of their ADHD medication or other medications?”

First, having ADHD is a risk factor for later nicotine and substance use.1 Clinicians see a lot of people who have ADHD and use marijuana. In fact, it’s the drug that’s most commonly misused by people with ADHD.1 We know that marijuana use is associated with short-term neuropsychological impairment that persists from two to eight hours after use. Marijuana use has been shown to impair executive function skills, which are the skills that allow us to plan, organize, solve problems, make decisions, and control emotions.2It’s important for you and your teen to understand that it takes up to eight hours to regain full thinking processes after smoking a joint or vaping. Your child should wait eight hours after using marijuana before they drive.

[Read: 5 Key Facts About ADHD and Substance Use Disorders]

Smoking marijuana at a young age may also carry serious long-term implications, like executive function challenges and permanent changes in brain function.3 4

Interestingly, researchers at the National Institutes of Health are studying this issue as part of a project called the Adolescent Brain and Cognitive Development Study (ABCD), the largest long-term study of brain development and child health ever conducted in the United States. One of the important questions they’re examining is: “Does early exposure to cannabis change vein structure and function?” So far, the data suggests yes.

To your question about the effects of marijuana use on ADHD medication: A study presented several years ago showed that smoking cannabis negated or diminished the positive impact of methylphenidate, or Ritalin. That finding reflects what I see clinically: If people are responding well to their ADHD medication, and they smoke too much, you see worsening of the ADHD response to the medication.

In terms of other drug interactions, if your teen is smoking or using cannabidiol, or CBD, and taking other medications, you should be concerned. CBD inhibits certain liver enzymes, which may impair drug metabolism, leading to the need to increase the levels of the medication being prescribed.

[Read: Is Your Teen Vaping? Why ADHD Brains Get Addicted & How to Quit]

To induce your child to use less (or no) marijuana, don’t make it easy for them to do so. Announce that, in one week, you’re going to go through the house, and their room, and you’re going to throw out any marijuana you find. Then, follow through and monitor routinely.

And by the way, as a parent, if you’re smoking or vaping marijuana, it is time to break your own habit. People say to me, “Oh, my kid doesn’t know I smoke or vape.” My response is, “Of course they know you smoke or vape. And not only that, they’re probably smoking or vaping your marijuana.”

Effects of Marijuana: Next Steps

Timothy Wilens, M.D., is an associate professor of psychiatry at Harvard Medical School.

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