Growing Up High: Is Cannabis a Problem?

By Ofer Zur, Ph.D.

Cannabis is the most commonly used substance among adolescents after alcohol. Unfortunately, more and more adolescents and adults believe that cannabis use can pose no threat. Obviously this belief may undermine prevention efforts.

The US Dept. of Health and Human Services reported the percent of young people in the US using cannabis at least once in the past month:

  • 5% of students in 8th grade;
  • 14% in 10th grade;
  • 23% in 12th grade;and 22% of college students and young adults.
  • Current cannabis use among students in 12th grade has increased in the past 10 years. (Unlike drinking alcohol or smoking tobacco which have decreased.)

Some say the current spread of legalization of cannabis in the U.S. and across Canada means that, for adolescents, there is a ‘new vitamin’ – and it’s called THC.

But what does adolescent use of cannabis really mean? Does exposing a growing brain to cannabis in the midst of the maturation of cognitive functions–such as working memory, decision-making, and impulse control–present any problems? Canadian neuroscientists recently studied the year-to-year changes in alcohol and cannabis use and cognitive function in a large sample of adolescents.

Cannabis was found to be linked to low cognitive functioning and impairments in working memory and inhibitory control, which is required for self-control. Further, cannabis use was also associated with deficits in memory recall and perceptual reasoning. In case you are wondering, alcohol use was not linked to impairments in these cognitive functions, suggesting cannabis could have more long-term effects than alcohol.

The researchers also analyzed the sex difference in cannabis response in the same sample of adolescents. Cannabis use was found to have a stronger effect on the memory functions of male students than female students. Both sexes were however, equally affected by cannabis on inhibitory control.

A Canadian researcher also found what he calls “schizophrenia-like” effects. Adolescent THC exposure also caused affective and cognitive abnormalities including deficits in social interactions, memory processing and anxiety regulation.

Researchers also found, what many of us could probably guess, cannabis disrupts motivation. Specifically, cannabis users have differences in encoding the value of the rewards and the effort cost when compared to healthy controls. And these differences affect how we make decisions and exert self-control when trying to avoid making bad decisions.

These findings support the hypothesis that adolescent cannabis use decreases motivation, known as “amotivation syndrome” and also increases the risk of turning to other drugs that promise a quick high with little effort – known as the “gateway hypothesis”.

Perhaps we should all be reconsidering the effects of growing up high. As we well know, adolescence is a time of critical brain development, and advancement of many cognitive functions that are not only predictive of long-term success, but the avoidance of long-term addiction.
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