Marijuana: Marijuana & the Teen Brain

Marijuana & Teens

Effects of Marijuana Use

  • Problems with memory and learning
  • Slowed reaction time
  • Impaired motor coordination, including driving skills
  • Altered judgment and decision-making, possibly leading to high-risk behaviors
  • Increased heart rate by 20-100%
  • Altered mood: calm and euphoric; anxiety, depression and paranoia
  • THC exposure during adolescence can affect brain development

Long-Term Risks

The most recent scientific studies show that heavy use of marijuana by teens interferes with normal brain development and may lead to lasting decreases in IQ.

  • Decline in IQ dose-dependent
  • Decline in IQ accounted for by adolescent onset of marijuana use
  • Cessation of use by age 38 did not change decline in IQ
  • Decline in all four indices of IQ: working memory, processing speed, perceptual reasoning, verbal comprehension
  • Friends/family noticed significantly more memory/attention span problems
(Source: Meier MH et al. Persistent cannabis users show neuropsychological decline from childhood to midlife. Proc. Natl. Acad. Sci. USA, 2012 Aug. 27; For more information see the video presentation by Christian Thurstone, MD, "Marijuana: The Blunt Truth".)

  • Possibility of addiction
  • Impairment beyond time of intoxication
  • Poor educational and career outcomes
  • Increased heart rate and irregular rhythms may trigger heart attack
  • Marijuana smokers have many of the chronic respiratory illnesses as tobacco smokers, including the chance for lung cancer
  • Marijuana has the potential to suppress immune systems and increase the disease process

Potential Mental Health Effects

  • Threat of increased psychotic symptoms in vulnerable users
  • Studies show an association between early marijuana use and schizophrenia
  • Marijuana is associated with depression, suicidal thoughts and suicide attempts
  • Research suggests THC use may increase the risk of mental illness by 40%

Can Marijuana Be Addictive?

The risk of addiction to marijuana is about 1 in 6 among those who start using as adolescents.

Although smoking marijuana has not led to fatal overdose, and risks posed by alcohol and other illicit or misused licit drugs are far greater, there is evidence that marijuana carries the possible consequence of dependency. Long-term use of marijuana can lead to compulsive seeking and abuse that interfere with normal life activities and research shows that approximately 9% of people who use marijuana became dependent.

School Performance

Young adults age 18 - 23 who did not complete high school report significantly higher rates of current marijuana use.

Adolescent marijuana use predicts less educational achievement. Adolescents using marijuana for the first time at 18 years or older (or never using) compared to those using by 15 years are:
  • 3.6 times more likely to get a HS degree
  • 2.3 times more likely to enroll in college
  • 3.7 times more likely to get a college degree
Students with an average grade of “D” or lower report significantly higher rates of current marijuana use compared to those with an average grade of “C” or higher.

What You Can Do

Learn More - Resources for Parents

Marijuana FactCheck

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