Sean McDowell | September 10, 2015

Does Pot Hurt the Teenage Brain?

Does Pot Hurt the Teenage Brain?

Marijuana is the most popular illicit drug in the world. Studies now show that the first cigarette a teen tries is more likely to be marijuana than tobacco. Although marijuana can be ingested in many ways, it is now popular for teens to vaporize marijuana through an e-cig.

It is interesting that many of the elites in our culture are so strongly against tobacco but seem strangely silent about the negative effects of marijuana. So, is marijuana harmful to teens? Should we be concerned?

Recently I was reading The Teenage Brain by Dr. Frances Jensen, a neuroscientist. She has some strong words of caution for those who uncritically endorse the legalization of marijuana without considering the negative effects it will have on teens:

“In the last five years, marijuana abuse has been responsible for almost two-thirds of admissions of teenagers, ages fifteen to nineteen, to rehabilitation centers, compared with less than a third for alcohol” (142).

“The pot smoked by kids today is not the pot you might have smoked in college. In 1985, THC concentration in marijuana averaged out to less than 4 percent. In 2009 the average THC concentration was close to 10 percent. The most critical issue for teens is that THC disrupts the development of neural pathways” (146).

“In their early teens, pot-smoking adolescents have shown to have smaller whole brain volume, reduced gray matter, and increased damage to white matter compared with non-users” (148).

“Forgetfulness is the most widely reported cognitive deficit associated with marijuana use” (150).

“Even more worrisome is the link between chronic pot use during adolescence and decrease in IQ” (152).

“Marijuana use has also been observed to inhibit functioning in the areas of the cortex that play a critical role in recognizing errors…” (152).

“A study done in Great Britain found evidence to support the conclusion that cannabis use was an important causal factor in the development of schizophrenia and that smoking marijuana doubles the risk of psychosis” (154).

“…early marijuana use was linked to a 50 percent increase in the risk of having an episode of clinical depression after age seventeen (155).

“Why is this happening? Once again basic research is showing us that marijuana exposure during adolescent brain development can change the receptors in multiple areas of the brain—not only in the hippocampus and cortex, resulting in changes in cognition, but also in the nucleus accumbens in a way that can increase the ‘addictability’ of the brain to other substances” (155).

“Smoking marijuana cigarettes is equal to smoking a full pack of tobacco cigarettes, according to the American Lung Association” (156).

The conclusion to the book is most striking. Parents, youth leaders, teachers, and students must read her conclusions and take them to heart:

“The implication of current marijuana research for teenagers is profound. Manipulating or interrupting this important stage of development with cannabis could change the entire trajectory of their brain development, with some deficits not appearing until much later in life. If, as parents, teacher, and guardians, we ignore the science, we do so at the peril of our own children” (158).

Sean McDowell, Ph.D. is an assistant professor of Christian Apologetics at Biola University, a best-selling author of over 15 books, an internationally recognized speaker, and a part-time high school teacher. Follow him on Twitter: @sean_mcdowell. He blogs regularly at

Sean McDowell, Ph.D. is a professor of Christian Apologetics at Biola University, a best-selling author, popular speaker, and part-time high school teacher. Follow him on Twitter: @sean_mcdowell, TikTok, Instagram, and his blog: