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Research Report Series - Marijuana Abuse

How does marijuana use
affect school, work,
and social life?

Students who smoke marijuana get lower grades and are less likely to graduate from high school, compared with their nonsmoking peers.^22,47,48,49 In one study, researchers compared marijuana smoking and nonsmoking 12th-graders' scores on standardized tests of verbal and mathematical skills. Although all of the students had scored equally well in 4th grade, those who were heavy marijuana smokers, i.e., those who used marijuana seven or more times per week, scored significantly lower in 12th grade than nonsmokers.⁹

Workers who smoke marijuana are more likely than their co-workers to have problems on the job. Several studies have associated workers' marijuana smoking with increased absences, tardiness, accidents, workers' compensation claims, and job turnover. A study among municipal workers found that employees who smoked marijuana on or off the job reported more "withdrawal behaviors" - such as leaving work without permission, daydreaming, spending work time on personal matters, and shirking tasks - that adversely affect productivity and morale.⁵⁰

Depression¹⁹, anxiety^19,20, and personality disturbances⁵ are all associated with marijuana use. Research clearly demonstrates that marijuana use has the potential to cause problems in daily life or make a person's existing problems worse. Because marijuana compromises the ability to learn and remember information, the more a person uses marijuana the more he or she is likely to fall behind in accumulating intellectual, job, or social skills. Moreover, research has shown that marijuana's adverse impact on memory and learning can last for days or weeks after the acute effects of the drug wear off.^9,35

For example, a study of 129 college students found that among heavy users of marijuana, those who smoked the drug at least 27 of the preceding 30 days, critical skills related to attention, memory, and learning were significantly impaired, even after they had not used the drug for at least 24 hours.³⁵ The heavy marijuana users in the study had more trouble sustaining and shifting their attention and in registering, organizing, and using information than did the study participants who had used marijuana no more than 3 of the previous 30 days. As a result, someone who smokes marijuana once daily may be functioning at a reduced intellectual level all of the time. More recently, the same researchers showed that a group of long-term heavy marijuana users' ability to recall words from a list was impaired 1 week following cessation of marijuana use, but returned to normal by 4 weeks.⁵² An implication of this finding is that even after long-term heavy marijuana use, if an individual quits marijuana use, some cognitive abilities may be recovered.

Another study produced additional evidence that marijuana's effects on the brain can cause cumulative deterioration of critical life skills in the long run. Researchers gave students a battery of tests measuring problem-solving and emotional skills in 8th grade and again in 12th grade.⁵³ The results showed that the students who were already drinking alcohol plus smoking marijuana in 8th grade started off slightly behind their peers but that the distance separating these two groups grew significantly by their senior year in high school. The analysis linked marijuana use, independently of alcohol use, to reduced capacity for self-reinforcement, a group of psychological skills that enable individuals to maintain confidence and persevere in the pursuit of goals.

Can marijuana use
during pregnancy harm the baby?

Research has shown that babies born to women who used marijuana during their pregnancies display altered responses to visual stimuli, increased tremulousness, and a high-pitched cry, which may indicate problems with neurological development.⁵⁴ During infancy and preschool years, marijuana-exposed children have been observed to have more behavioral problems and to perform tasks of visual perception, language comprehension, sustained attention, and memory more poorly than nonexposed children do.^55,56 In school, these children are more likely to exhibit deficits in decision-making skills, memory, and the ability to remain attentive.^55,56

Is marijuana use addictive?

Long-term marijuana use can lead to addiction for some people; that is, they use the drug compulsively even though it often interferes with family, school, work, and recreational activities. According to the 2001 National Household Survey on Drug Abuse, an estimated 5.6 million Americans age 12 or older reported problems with illicit drug use in the past year. Of these, 3.6 million met diagnostic criteria for dependence on an illicit drug. More than 2 million met diagnostic criteria for dependence on marijuana/hashish.⁵⁷ In 1999, more than 220,000 people entering drug abuse treatment programs reported that marijuana was their primary drug of abuse.⁵⁸

Along with craving, withdrawal symptoms can make it hard for long-term marijuana smokers to stop using the drug. People trying to quit report irritability, difficulty sleeping, and anxiety.^59,60 They also display increased aggression on psychological tests, peaking approximately 1 week after they last used the drug.⁶¹