The Damaging Effects of Cannabis on the ADHD Brain

Cannabis is used by a startling number of people with attention deficit hyperactivity disorder (ADHD). Studies show that more than half of daily and non-daily cannabis users have ADHD¹, and about one-third of adolescents with ADHD report cannabis use². People with ADHD are also three times as likely as their neurotypical peers to have ever used marijuana.³

As with other popular substances, cannabis is commonly abused. In fact, the risk of developing cannabis use disorder (CUD), a problematic pattern of cannabis use linked to clinically significant impairment, is twice as high in people with ADHD³. Contrary to popular belief, individuals can be mentally and chemically dependent on and addicted to cannabis. Contemporary marijuana has concentrations of THC higher than historically reported, which exacerbates this. What’s more, the adverse effects of cannabis are especially amplified in people with ADHD.

What are the Negative Effects of Cannabis?

Tetrahydrocannabinol (THC), one of cannabis’ active compounds, inhibits neuronal connections and effectively slows the brain’s signaling process. THC also affects the brain’s dendrite architecture, which controls processing, learning, and the overall health of the brain. Science has not yet fully determined whether THC’s effects are reversible; some parts of the brain show healthy neuronal growth after cannabis use stops, but other parts do not.

Short-term and long-term cannabis use also impairs:

• Motivation (hampering effect)
• Memory, especially in people under 25, by altering the function of the hippocampus and orbitolfrontal cortex, where much of memory is processed
• Performance on complicated task performance with many executive steps. Studies have shown, for example, that driving ability, even while not under the influence, can be impaired in regular marijuana users

Cannabis use may also lead to the following health-related impairments:

• Chronic bronchitis
• Chronic obstructive pulmonary disease (COPD)
• Emphysema
• Cannabinoid hyperemesis syndrome (characterized by severe bouts of vomiting and dehydration)
• Elevated resting heart rate

Cannabis use may exacerbate disorders like paranoia, panic, and mood disorder. Studies have also found that increased cannabis consumption can uniquely contribute to elevating suicide risk, even when controlling for underlying mental health disorders, like mood disorder or anxiety ^{4 5}. Individuals who begin regular cannabis use also exhibit more suicidal ideation, even when controlling for pre-existing mood disorders, studies show.^{6 7}

What is Cannabis Use Disorder (CUD)?

Cannabis is addictive — 9 percent of people who use cannabis regularly will become dependent on it ⁸. This figure rises to 17 percent in those who start using cannabis in adolescence.⁹

CUD can develop after extended cannabis use. It is diagnosed when at least two of the following occur within a 12-month period:

• Taking cannabis in larger amounts over longer periods of time
• Difficulty quitting cannabis use
• Strong desires or cravings to use cannabis
• Lots of time spent trying to obtain, use, or recover from cannabis
• Problems with work, school, or home because of interference from cannabis use
• Social or interpersonal problems due to cannabis use
• Activities given up or reduced because of cannabis use
• Recurrent cannabis use in physically hazardous situations, such as driving
• Physical or psychological problems caused or exacerbated by cannabis use
• Tolerance to cannabis
• Withdrawal from cannabis

How Does Cannabis Affect the ADHD Brain?

Cannabis use impairs areas and functions of the brain that are also uniquely impaired by ADHD.

The substance’s negative effects are most harmful to developing brains. Many studies show that usage earlier in life, particularly before the age of 25, predicts worse outcomes. One study found that heavy marijuana use in adolescence was associated with a loss of 8 IQ points, on average, in adulthood ¹⁰. Another study found that people under age 18 are four to seven more times at risk for CUD compared to adults.¹¹

People with ADHD, whose brain development is delayed by slowly maturing frontal lobes, are thus more vulnerable to cannabis’ effects on neuronal connections. Some of these impairments may be irreversible.

Cannabis can also interact significantly with some ADHD medications. Research studies have shown that methylphenidate (Ritalin, Concerta) reacts significantly with the substance, and can cause increased strain on the heart.¹²

Other studies show that the use of cannabis can decrease the effect of a stimulant medication¹³. An individual trying to treat their ADHD with stimulants is actually placing themselves at a disadvantage, since the cannabis is impacting them negatively and making the medication less effective.

The increased risk of suicide associated with cannabis use further complicates marijuana among individuals with ADHD, who already face an elevated risk for suicide compared to neurotypical individuals ¹⁴.

[ADHD Directory: Find an ADHD Specialist or Clinic Near You]

What Draws People with ADHD to Cannabis?

Cannabis activates the brain’s reward system, and releases dopamine at levels higher than typically observed. In low-dopamine ADHD brains, THC thus can be very rewarding.

Many people with ADHD also claim that cannabis helps them focus, sleep, or seemingly slow the pace of their thoughts. One analysis of internet threads found that 25 percent of relevant posts described cannabis as therapeutic for ADHD, while 5 percent indicated that it is both therapeutic and harmful ¹⁵. Despite some users reporting short-term improvement in symptoms, there is currently no evidence that suggests cannabis is medically or psychologically helpful for managing ADHD in the long-term.

Cannabis’ increased availability and legalization have increased accessibility; many cannabis products are falsely marketed as medicinal for ADHD.

Also contributing to an increased likelihood of cannabis use and CUD among individuals with ADHD is the prevalence of low self-esteem, sleep problems, poor impulse control, and sensation-seeking tendencies in this population.

How is Cannabis Use Disorder Treated in People with ADHD?

There is no approved medication to treat CUD — treatment generally means teaching patients strategies to maintain sobriety. Treatment can include talk therapies, like cognitive behavioral therapy (CBT) and dialectical behavior therapy (DBT), and participating in support groups like Marijuana Anonymous.

One small but insightful study looking at motivations to quit cannabis use in a group of adults with ADHD found that saving money was a major contributing factor ¹⁶. The same study found that the most common strategy for maintaining abstinence was breaking social connections with people who smoke marijuana.

Treating and targeting ADHD itself in a patient that has CUD is also essential. Stimulant medication can be implemented as part of ADHD treatment, and it is not considered a violation of sobriety.

How Should a Parent Help a Teen with ADHD Who Is Using Cannabis?

It’s normal for parents to experience a range of emotions after discovering that their child is using cannabis. The initial gut reaction or emotion is understandably anger and disappointment, but it’s best to release these feelings prior to engaging in conversation. Any dialogue with teens must be done in a controlled, calm way — teens will not listen to parents who are yelling and blurting out things they will later regret.

Seeking consultation with a doctor, pediatrician, or therapist who has experience in substance abuse can help, especially for parents who are struggling with their owns feelings and reactions toward their child.

The next step is for parents to educate themselves on cannabis and how it can be appealing. Parents should try to proactively see what their child might be experiencing, and why they might have turned to the substance. When the conversation does start, parents should work deliberately not to shame their child, and instead focus on understanding their child’s experience on cannabis.

Parents should calmly ask questions like:

• “I found this and I’m concerned, but I’d like to know what the appeal of this is for you?”
• “What does this do for you?”
• “How did you feel the very first time that you did this?”

While parents are encouraged to have calm and thoughtful conversations with their teen, they should also set boundaries and consequences for substance use to remind their child that it is not acceptable. Without shaming, parents must establish rules that discourage substance use, especially in the household.

Many parents will say that they would rather have their child smoke in the house than outside with others. But this mentality doesn’t stop teens from smoking or using anywhere else. Instead, allowing at-home use communicates a sense of permission associated with substance use.

If teens say they are simply experimenting, they should know that experimentation can quickly turn into something more dangerous. Parents should inform them that teens with ADHD are at higher risk for addiction. Teens should also be aware, if they aren’t by this point, of any family history of addiction, which also has a genetic component.

Placing limits on smoking can create some backlash. Teens and young adult may be so gripped by the substance they they are willing to lie about using it to parents. Parents should approach their child if they suspect they are using, even after rules are in place, but should keep in mind that this substance, like any, can have people not always be truthful. That’s very different from thinking that their child can’t be trusted and is a liar.

Children should be reminded that they are loved and that their health is most important. Smoking marijuana doesn’t mean that parents have failed or that they’ve done a bad job with their children. There’s a terrible stigma on addiction surrounding character and morality — it’s important to remember that teens aren’t using drugs because they are bad people. Very, very good people are addicted to substances or experiment with them.

The information in this article is based on Dr. Roberto Olivardia’s two-part Marijuana and the ADHD Brain webinar series. The first part, “Marijuana and the ADHD Brain: How to Identify and Treat Cannabis Use Disorder in Teens and Young Adults” was broadcast live on February 26, 2020. “Marijuana and the ADHD Brain, Part 2” was broadcast live on March 26, 2020.

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