Effects of Heavy Marijuana Use on Learning and Social Behavior
Depression, anxiety, and personality disturbances have been associated with marijuana use. Research clearly demonstrates that marijuana has 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.
Students who smoke marijuana get lower grades and are less likely to graduate from high school, compared with their non-smoking peers. A study of 129 college students found that, for 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. 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 every day may be functioning at a reduced intellectual level all of the time.
More recently, the same researchers showed that the ability of a group of long-term heavy marijuana users to recall words from a list remained impaired for a week after quitting, but returned to normal within 4 weeks(29). Thus, it is possible that some cognitive abilities may be restored in individuals who quit smoking marijuana, even after long-term heavy use.
Workers who smoke marijuana are more likely than their coworkers to have problems on the job. Several studies associate workers’ marijuana smoking with increased absences, tardiness, accidents, workers’ compensation claims, and job turnover. A study of municipal workers found that those who used 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(30). In another study, marijuana users reported that use of the drug impaired several important measures of life achievement including cognitive abilities, career status, social life, and physical and mental health(31).
Effects on Pregnancy
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 neurological problems in development(32). During infancy and preschool years, marijuana-exposed children have been observed to have more behavioral problems than unexposed children and poorer performance on tasks of visual perception, language comprehension, sustained attention, and memory(33, 34). In school, these children are more likely to exhibit deficits in decision-making skills, memory, and the ability to remain attentive(35, 36, 37).
Long-term marijuana use can lead to addiction for some people; that is, they use the drug compulsively even though it interferes with family, school, work, and recreational activities. Drug craving and withdrawal symptoms can make it hard for long-term marijuana smokers to stop using the drug. People trying to quit report irritability, sleeplessness, and anxiety(38). They also display increased aggression on psychological tests, peaking approximately one week after the last use of the drug(39).
Scientists have found that whether an individual has positive or negative sensations after smoking marijuana can be influenced by heredity. A 1997 study demonstrated that identical male twins were more likely than non-identical male twins to report similar responses to marijuana use, indicating a genetic basis for their response to the drug(40). (Identical twins share all of their genes.)
It also was discovered that the twins’ shared or family environment before age 18 had no detectable influence on their response to marijuana. Certain environmental factors, however, such as the availability of marijuana, expectations about how the drug would affect them, the influence of friends and social contacts, and other factors that differentiate experiences of identical twins were found to have an important effect.
Treating Marijuana Problems
The latest treatment data indicate that, in 2000, marijuana was the primary drug of abuse in about 15 percent (236,638) of all admissions to treatment facilities in the United States. Marijuana admissions were primarily male (76 percent), White (57 percent), and young (46 percent under 20 years old). Those in treatment for primary marijuana use had begun use at an early age; 56 percent had used it by age 14 and 92 percent had used it by 18.
One study of adult marijuana users found comparable benefits from a 14-session cognitive-behavioral group treatment and a 2-session individual treatment that included motivational interviewing and advice on ways to reduce marijuana use. Participants were mostly men in their early thirties who had smoked marijuana daily for more than 10 years. By increasing patients’ awareness of what triggers their marijuana use, both treatments sought to help patients devise avoidance strategies. Use, dependence symptoms, and psychosocial problems decreased for at least 1 year following both treatments; about 30 percent of users were abstinent during the last 3-month followup period.
Another study suggests that giving patients vouchers that they can redeem for goods—such as movie passes, sporting equipment, or vocational training—may further improve outcomes.
Although no medications are currently available for treating marijuana abuse, recent discoveries about the workings of the THC receptors have raised the possibility of eventually developing a medication that will block the intoxicating effects of THC. Such a medication might be used to prevent relapse to marijuana abuse by lessening or eliminating its appeal.