Researchers have been trying to track down the link between cannabis use and intelligence for decades. You know the stereotypes. But what does the research show? One of the longest studies ever conducted has finally confirmed it. Cannabis does not lower teen IQ.
In October 2012, researchers issued a major study conducted over thirty years. The study claimed that cannabis consumption lowered the user’s “intelligence quotient” or IQ. According to the study, those effects were worse if the subject was a persistent cannabis user. And it’s not the only study that has claimed marijuana causes a decline in neuropsychological ability.
Studies Confirm Cannabis Doesn’t Lower Teen IQ
But four years later, researchers released a study that challenged the 2012 research. In fact, there were two studies. Both studies compared two groups of adolescents. One group of teens used cannabis. The other control group abstained from smoking or consuming marijuana. Researchers conducted the first study in universities in London and Bristol. Their findings confirm that there is no measurable link between the use of cannabis and lower teen IQ.
The specifics of the study paint a clearer picture. 2235 teenagers were part of the study. Those that used cannabis more than 50 times over the course of a year showed same teen IQ and educational outcomes as their peers who abstained from pot.
There is still a lot of debate about how cannabis impacts neuropsychological functions associated with learning and memory. But this study is worth considering because it was able to take into account other significant factors that influence intelligence.
Smoking cigarettes, it turns out, is one of the factors that can decrease teen IQ. So are depression and stress. Importantly, the study did not include teens who use cannabis heavily or regularly. But researchers say moderate cannabis use may have a lower impact on cognition than other studies suggest.
Lower Teen IQ Linked to Other Factors, Not Cannabis
Researchers in the United States conducted the second study. This study is fascinating because it was done on twins. Over a period of 10 years, the study looked at the effects of marijuana on 2,000 teen twins.
In each set of twins, one twin was a regular consumer of cannabis, and the other was not. The results are complex, but give a clearer picture of the relationship between cannabis and IQ.
The study reported that yes, marijuana users had a lower IQ test scores than their non-using counterparts. Furthermore, teen cannabis users showed a significant decline in “crystallized intelligence” between early and late adolescence.
It sounds like marijuana does make teens stupid. However, the researchers couldn’t find any supporting evidence that lower intelligence was linked to the frequency or dose of marijuana use.
So what gives? It turns out that a decline in IQ is more likely related to family and emotional factors. The study did say that family and emotional problems are linked to “marijuana initiation.” However, cannabis use itself didn’t cause a drop in IQ. It just happened to be present whenever other factors that do lower IQ were involved.