Effect of Cannabis on Teenage Brain
Since the legalization of cannabis either medicinally or recreationally in a majority of states, there has been growing concern about the effects of cannabis on the teenage brain. There have been claims that cannabis use among adolescents will lower their IQ (intelligence quotient) while others have even claimed it can lead to schizophrenia. This article will review recent studies on the matter and what was found.
2016 – Longitudinal Twin Studies
In a 2016 longitudinal study, it was found that cannabis users had lower test scores relative to nonusers and showed a decrease in “crystallized” intelligence (the accumulation of knowledge, facts, and skills that are acquired throughout life) between preadolescence and late adolescence. However, there was no relationship found between frequent cannabis use to a decline in their IQ.
In addition, when comparing cannabis-using twins to their abstinent siblings, it failed to show any significant decline in IQ among the ones using cannabis. As stated in the study, the results of these studies suggest that any observed decrease in IQ was “not a direct result of [cannabis] exposure, but rather attributable to familial factors that underlie both [cannabis] initiation and low intellectual attainment.”
2018 – Evaluation of Previous Studies
In a 2018 evaluation of previous studies on the matter, a research group pooled data from 69 studies involving more than 2,100 cannabis users. After examining the data, it was concluded that any associations between cannabis use among adolescents and a decrease in cognitive functioning “is small and may be of questionable clinical importance for most individuals.”
The study also found that after 72 hours of abstinence, the memory and thinking deficits of heavy users diminishes to the point of insignificance when compared with the intellectual capacity of nonusers.
Psychosis & Schizophrenia
In addition to its effect on an adolescent’s cognitive ability and IQ, there have been some claims that early use of cannabis can lead to mental illness, such as schizophrenia. However, the validity of this claim is questionable, if not unproven. If anything, those who are genetically predisposed to developing some form of psychosis (like schizophrenia) are also more likely to use cannabis.
Researchers also have found that if you carry certain types of specific genes that affect brain chemistry, cannabis use may raise the chance a person developing schizophrenia. One of those genes is called “AKT1.” One study found that the risk of psychosis among those with this variant was seven times higher for those who used cannabis daily compared with those who used it infrequently or used none at all. However, correlations is not causation and it may be that those who are more predisposed genetically to developing some form of psychosis are also more likely to use cannabis.
In sum, recent studies on whether using cannabis during adolescence decreases intelligence shows any correlation between the two are weak, if not non-existent. In addition, if there is any correlation between early cannabis use and developing schizophrenia, it is more likely based on a genetic predisposition than the actual use of cannabis.
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