A Little Weed Won’t Hurt Anyone? Well, Maybe Teenagers!

Twenty-three states have made medicinal marijuana legal and four additional states, as well as Washington DC, have made its recreational use legal in recent years. This blog is not to refute or support these laws, rather to examine a study about the effects of marijuana on the developing brain, in particular, the developing teenage brain.


According to an article published by NPR, a recent survey showed that 60 percent of high school seniors said marijuana was safe and 23 percent admitted to using marijuana in the past 30 days. So what impact does a steady cannabis intake have on the developing, teenage brain?

Krista Lisdahl, director of the brain imaging and neuropsychology lab at University of Wisconsin, explains that the brain is larger during childhood and reduces in size during our teenage years to make our processing faster and more efficient. Lisdahl says that using cannabis as a teenager is actually the worse time because it can disrupt brain development.

Lisdahl cites several studies with somewhat mixed results. In one study, researchers analyzed IQ information from marijuana users in New Zealand (experimental group) and IQ information from nonusers in New Zealand (control group). They tracked the groups from childhood until age 38 and found that the experimental group lost approximately 8 IQ points over that course of time. Those in the experimental group that smoked the most cannabis saw the greatest decrease in IQ. They also performed worse in memory and decision making than the control group.

However, when using human subjects, there is always the dilemma of control factors. For example, how does genetics and diet play a role in the IQ of each individual? The amount, source, potency and frequency of cannabis use are all factors that should remain the same within the experimental group as well. Additionally, does cannabis affect boys and girls differently?

In another article published by the APA (American Psychological Association) , Lisdahl states that most of the studies carried out on the long term effects of cannabis focus on heavy users and it is unclear if there is a safe level of use. A study called the Adolescent Brain and Cognitive Development is now ongoing and it will follow 10,000 individuals in the United States over a decade, beginning at the ages 9-10, to hopefully arrive at a definitive conclusion.

With the legalization of marijuana across the country, we owe it to ourselves to determine the effects of cannabis, both long and short term, on the developing mind. According to a survey cited in the NPR article, six percent of high school seniors use cannabis daily and today’s cannabis is higher in THC, the main hallucinogen. If further studies uphold the findings in the New Zealand study, measures should be taken to keep cannabis away from teenagers.

In conclusion, you probably shouldn’t do marijuana because it is illegal in most states. However if you choose to do so, maybe wait until more concrete studies are conducted and results come in. In the long run, it could save you some IQ points.

Works Cited


Neighmond, Patti. “Marijuana May Hurt The Developing Teen Brain : Shots …” NPR. N.p., 03 Mar. 2014. Web. 20 Oct. 2016.

Weir, Kirsten. “APA, ” Marijuana and the Developing Brain.” APA. N.p., Nov. 2015. Web. 20 Oct. 2016.

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