Heavy Marijuana Use Affects Learning and Social Skills

Strong Link Found to Marijuana and Lowered Intellect Levels

young people smoking marijuana

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Numerous scientific research studies have shown that heavy marijuana use can negatively affect a person's learning abilities and social skills. The studies suggest that a person who smokes marijuana every day may be functioning at a reduced intellectual level even during periods of brief abstinence.

The upside is after four weeks of quitting the drug, in most cases, people who had used marijuana for long periods of time could recover their cognitive abilities. Although, there is some evidence to the contrary for children under the age of 18.

What the Research Says

The National Institute on Drug Abuse (NIDA) looked at 11 scientific research studies and concluded that heavy marijuana use, which is defined as smoking marijuana 27 days in 30 days, has a significant impact on person's ability to learn, remember what they learned, and function in society.

General Effects of Heavy Marijuana Use

According to the research results, heavy marijuana use revealed a link to several problems in personality and memory.

  • The potential link to depression, anxiety, and personality disorders.
  • Decrease the ability to learn and remember information, making it more likely to fall behind the norm on developing intellectual, job, and social skills.
  • Dampened the ability to remember and learn for days and weeks after abstinence from marijuana use.

Effects of Daily Marijuana Use on Students

The research results of daily marijuana use by students also showed problems in focus, scholastic performance, and memory.

  • Students were getting lower grades and becoming less likely to graduate, compared to students who did not use marijuana.
  • Students had significantly impaired skills related to attention, memory and learning even after not using marijuana for 24 hours.
  • Students had problems in sustaining and shifting attention.
  • Students had problems with the ability to register, organize and use information, even compared to occasional users of marijuana.
  • Students had an impaired ability to recall words from a list a week after quitting marijuana use.

Effects on Work Performance

Findings from the research of heavy marijuana users in the workplace showed problems in absences, tardiness, accidents, and cognitive abilities.

  • People in the workplace who used marijuana were more likely to experience increased absences (75 percent), tardiness, accidents, workers' compensation claims, and job turnover.
  • People in the workplace who tested positive for marijuana use had 55 percent more industrial accidents and 85 percent more injuries compared to non-marijuana users.
  • Heavy marijuana abusers self-report that their use of the drug had negative effects on their cognitive abilities, career status, social life, and physical and mental health.​

Consequences of Early Marijuana Use

A person's brain is still developing up until the early 20s. Experts agree that the later someone begins using marijuana the better.

A Duke University study found that children who smoke marijuana at least weekly before age 18 displayed lasting harm to their intelligence, attention, and memory compared with those who began using marijuana after age 18.

The study also found that, unlike adults, quitting marijuana use did not entirely reverse the cognitive damaged caused by regular marijuana use.

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Article Sources

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Additional Reading

  • Pope HG, Gruber AJ, Hudson JI, et al. "Neuropsychological Performance in Long-Term Cannabis Users." Archives of General Psychiatry 58(10):909–915, 2001.