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Marijuana: Effects on the adolescent and young adult brain

By Michael D. Zito, Ph.D.

Many parents have expressed concern that legalization of marijuana for adults could increase adolescent and young adult use. Their concern has merit because teen and young adult brains are not fully developed until age 25. In my experience, a big problem is that users usually don’t think about the adverse effects of marijuana and only focus on the “fun” part. For example, I asked a teen marijuana user this question, “If I offered you a smokable substance that gives you euphoria for 1-2 hours which alters the balance of important brain neurotransmitters (serotonin, norepinephrine, dopamine and Gaba), puts carcinogens in your lungs and you will feel lethargic and in a “down mood” until your brain chemistry recovers 24 to 48 hours later, would you take it?, the answer was “no way, that sounds horrible, I would never agree to that”. He was in shock when I informed him that is what inhaled marijuana does to the body. Edibles don’t have the air borne carcinogens but still affect the brain chemistry and I have seen problems with overdosing often resulting in hospital visits for paranoia, panic attacks and/or psychosis.

Another problem that is often not recognized is the poor decision making resulting from regular marijuana use. Good decision making is facilitated by considering both the pros and the cons. With regular marijuana use, the brain pleasure centers get over stimulated and draw the person to consider only the pros (I like it, feels good, it’s fun) and not the negatives. This results in poor decision making which becomes chronic with persistent use. I asked a client who was expelled from her university, “if you knew that getting caught the 3rd time using marijuana would get you expelled and you still did it, what were you thinking?” She said she only thought of the “fun” part and did not consider the consequences because she didn’t think she’d get caught.” This is a great example of how substances contribute to poor decision making.

Research on long term effects for adolescents and young adults has found that regular (2-3 times per week) use of marijuana for at least 6 months: shrinks gray matter in the brain, reduces brain cells, inhibits learning and memory, promotes lung and heart damage (inhaled form has same toxins as cigarettes), lowers academic motivation, increases chance of addiction and suicide risk, and drops IQ 6-8 points. Short term effects include increase in heart rate and respiration, sedation/high, and poor motor coordination, attention and focus. In general, use increases the risk of anxiety/panic, psychosis, depression, and medical problems later in life.

So, what should parents do?

  • Talk with your teens and young adults about the consequences of use.
  • Help your child develop the ability to say “no” in social situations.
  • Keep them involved in activities within reason since boredom often promotes use.
  • If your child takes an anti-anxiety or anti-depression medication, help them realize that marijuana counteracts those medications.

Michael D. Zito, Ph.D. is a licensed psychologist (#3599) with offices in Warren and Morristown. He practices clinical and sport psychology with children through adults and can be reached at Dr. Zito welcomes your questions and ideas for future articles.