Use of marijuana for even one year, can affect long-term mental health.
See also, Marijuana and Marijuana
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.
Workers who smoke marijuana are more likely than their coworkers 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 postal workers found that employees who tested positive for marijuana on a pre-employment urine drug test had 55 percent more industrial accidents, 85 percent more injuries, and a 75 percent increase in absenteeism compared with those who tested negative for marijuana use.48
Effects of Marijuana Use Include
- More problems on the job
- Greater job turnover rate
- 55% more industrial accidents
- 85% More injuries
- 75% greater absenteeism
, and personality disturbances  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.
In one study of cognition, adults were matched on the basis of their performance in the 4th grade on the Iowa Test of Basic Skills. They were evaluated on a number of cognitive measures including the 12th-grade version of the Iowa Test. Those who were heavy marijuana smokers scored significantly lower on mathematical skills and verbal expression than nonsmokers.9
Psychological effects of marijuana use can include,
Cognitive Effects of Marijuana Use often include
- personality disturbances
- Loss in memory ability
- Compromises ability to learn new information
- Reduced intellectual level
- Lower math skills
- Lower ability in verbal expression
Marijuana Effects - Impact on Memory
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.9,51 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.33
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.
- using information
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.51 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.52
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.
Quitting marijuana use may result in some recovery of cognitive abilities
Marijuana users themselves report poor outcomes on a variety of measures of life satisfaction and achievement. A recent study compared current and former long-term heavy users of marijuana with a control group who reported smoking cannabis at least once in their lives, but not more than 50 times.
Among heavy marijuana users
- Fewer completed college
- Had lower incomes than non-users
Despite similar education and incomes in their families of origin, significant differences were found on educational attainment and income between heavy users and the control group: fewer of the cannabis users completed college and more had household incomes of less than $30,000.
When asked how marijuana affected their cognitive abilities, career achievements, social lives, and physical and mental health, the overwhelming majority of heavy cannabis users reported the drug's deleterious effect on all of these measures.53
Users reported deleterious effects on
- cognitive abilities
- career achievements
- social lives
- physical health
- mental health
The Body's Natural THC-Like Chemicals
THC owes many of its effects to its similarity to a family of chemicals called the endogenous cannabinoids, which are natural Cannabis-like chemicals. Because a THC molecule is shaped like these endogenous cannabinoids, it interacts with the same receptors on nerve cells, the cannabinoid receptors, that endogenous cannabinoids do, and it influences many of the same processes.
Research has shown that the endogenous cannabinoids help control a wide array of mental and physical processes in the brain and throughout the body, including memory and perception, fine motor coordination, pain sensations,70 immunity to disease, and reproduction.71
When someone smokes marijuana, THC overstimulates the cannabinoid receptors, leading to a disruption of the endogenous cannabinoids' normal function. This overstimulation produces the intoxication experienced by marijuana smokers. Over time, it may alter the function of cannabinoid receptors, which, along with other changes in the brain, can lead to withdrawal symptoms and addiction.60,72,73
Can marijuana use
during pregnancy harm the baby?
Research has shown that some 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. 54,75
During the preschool years, marijuana-exposed children have been observed to perform tasks involving sustained attention and memory more poorly than nonexposed children do.55,56 In the school years, these children are more likely to exhibit deficits in problem-solving 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 2003 National Survey on Drug Use and Health (NSDUH), an estimated 21.6 million Americans aged 12 or older were classified with substance dependence or abuse (9.1 percent of the total population).
Of the estimated 6.9 million Americans classified with dependence on or abuse of illicit drugs, 4.2 million were dependent on or abused marijuana.57 In 2002, 15 percent of people entering drug abuse treatment programs reported that marijuana was their primary drug of abuse.58
Craving and withdrawal symptoms can make it hard for long-term marijuana smokers to stop using the drug.
Along with craving, withdrawal symptoms can make it hard for long-term marijuana smokers to stop using the drug.49 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
Early marijuana use contributes to likelihood of lifetime drug problems.
Importance of early intervention emphasized
In addition to its addictive liability, research indicates that early exposure to marijuana can increase the likelihood of a lifetime of subsequent drug problems. A recent study of over 300 fraternal and identical twin pairs, who differed on whether or not they used marijuana before the age of 17, found that those who had used marijuana early had elevated rates of other drug use and drug problems later on, compared with their twins, who did not use marijuana before age 17.
This study re-emphasizes the importance of primary prevention by showing that early drug initiation is associated with increased risk of later drug problems, and it provides more evidence for why preventing marijuana experimentation during adolescence could have an impact on preventing addiction.62
Pages Related to Marijuana Research, School, Grades and Risks
, Schizophrenia and Suicide Risk
Marijuana Mental Effects
, clinical study
and Medical Marijuana Use
Quit smoking help
- How to Quit Smoking
9. Block, R.I., and Ghoneim, M.M. Effects of chronic marijuana use on human cognition. Psychopharmacology 100(1-2): 219-228, 1993.
20. Brook, J.S.; Balka, E.B.; and Whiteman, M. The risks for late adolescence of early adolescent marijuana use. Am J Public Health 89(10):1549-1554, 1999.
33. Pope, H.G., and Yurgelun-Todd, D. The residual cognitive effects of heavy marijuana use in college students. JAMA 275(7):521-527, 1996.
45. Lynskey, M.; and Hall, W. The effects of adolescent cannabis use on educational attainment: A review. Addiction 95(11):1621-1630, 2000.
46. Kandel, D.B., and Davies, M. High school students who use crack and other drugs. Arch Gen Psychiatry 53(1):71-80, 1996.
47. Rob, M.; Reynolds, I.; and Finlayson, P.F. Adolescent marijuana use: Risk factors and implications. Aust NZ J Psychiatry 24(1):45-56, 1990.
48. Zwerling, C.; Ryan, J.; and Orav, E.J. The efficacy of preemployment drug screening for marijuana and cocaine in predicting employment outcome. JAMA; 264 (20): 2639-43, 1990.
49. Budney, A.J.; Moore, B.A.; Vandrey, R.G.; and Hughes, J.R. The time course and significance of cannabis withdrawal. J Abnorm Psychol 112(3):393-402, 2003.
50. Brook, J.S.; Cohen, P.; and Brook, D.W. Longitudinal study of co-occurring psychiatric disorders and substance use. J Acad Child and Adolescent Psych 37(3):322-330, 1998.
51. Pope, H.G.; Gruber, A.J.; Hudson, J.I.; Huestis, M.A.; and Yurgelun-Todd. D. Neuropsychological performance in long-term cannabis users. Arch Gen Psychiatry 58(10):909-915, 2001.
52. Scheier, L.M., and Botvin, G.J. Effects of early adolescent drug use on cognitive efficacy in early-late adolescence: A developmental structural model. Journal of Substance Abuse 7(4):397-404, 1996.
53. Gruber, A.J.; Pope, H.G.; Hudson, J.I.; and Yurgelun-Todd, D. Attributes of long-term heavy cannabis users: a case-control study. Psychological Medicine 33:1415-1422, 2003.
54. Lester, B.M., and Dreher, M. Effects of marijuana use during pregnancy on newborn crying. Child Development 60(23/24):764-771, 1989.
55. Fried, P.A. The Ottawa prenatal prospective study (OPPS): Methodological issues and findings. It's easy to throw the baby out with the bath water. Life Sciences 56:2159-2168, 1995.
56. Fried, P.A.; and Smith, A.M. A literature review of the consequences of prenatal marihuana exposure: An emerging theme of a deficiency in aspects of executive function. Neurotoxicology and Teratology 23(1): 1-11, 2001.
57. Substance Abuse and Mental Health Services Administration. Results from the 2003 National Survey on Drug Use and Health: National Findings. NSDUH Series H-25. DHHS Pub. No. (SMA) 04-3964. Rockville, MD: SAMHSA, 2004.
58. Substance Abuse and Mental Health Services Administration. Treatment Episode Data Set (TEDS): 1992-2002, National Admissions to Substance Abuse Treatment Services. DASIS Series: S-23, DHHS Pub. No. (SMA) 04-3965. Rockville, MD: DHHS, 2004.
59. Haney, M.; Ward, A.S.; Comer, S.D.; Foltin, R.W.; and Fischman, M.W. Abstinence symptoms following smoked marijuana in humans. Psychopharmacology 141:395-404, 1999.
60. Budney, A.J.; Hughes, J.R.; Moore, B.A.; and Novy, P.L. Marijuana abstinence effects in marijuana smokers maintained in their home environment. Arch Gen Psychiatry 58:917-924, 2001.
61. Kouri, E.M.; Pope, H.G.; and Lukas, S.E. Changes in aggressive behavior during withdrawal from long-term marijuana
use. Psychopharmacology 143:302-308, 1999.
71. Wenger, T.; Toth, B.E.; Juaneda, C.; Leonardelli, J.; and Tramu, G. The effects of cannabinoids on the regulation of reproduction. Life Sci 65(6-7):695-701, 1999.
72. Maldonado, R.; and Rodriguez de Fonseca, F. Cannabinoid addiction: Behavioral models and neural correlates. J Neuroscience 22(9):3326-3331, 2002.
73. Breivogel, C.S.; Scates, S.M.; Beletskaya, I.O.; Lowery, O.B.; Aceto, M.D.; and Martin, B.R. The effects of delta-9 tetrahydrocannabinol physical dependence on brain cannabinoid receptors. Euro J Pharmacology 459:139-150, 2003.
74. Piomelli, D.; Giuffrida, A.; Calignano, A.; and Rodriguez de Fonseca, F. The endocannabinoid system as a target for therapeutic drugs. TIPS 21:218-224, 2000.
75. Fried, P.A.; and Makin, J.E. Neonatal behavioural correlates of prenatal exposure to marihuana, cigarettes and alcohol in a low risk population. Neurotoxicology and Teratology 9(1):1-7, 1987
Glossary to Marijana pages
A chronic, relapsing disease characterized by compulsive drug-seeking and abuse and by long-lasting chemical changes in the brain.
Chemicals that help control mental and physical processes when produced naturally by the body and that produce intoxication and other effects when absorbed from marijuana.
Any substance that causes cancer.
A brain chemical, classified as a neurotransmitter, found in regions of the brain that regulate movement, emotion, motivation, and pleasure.
An area of the brain crucial for learning and memory.
Any chemical compound containing only hydrogen and carbon.
Having a specific effect on the mind.
Delta-9-tetrahydrocannabinol; the main active ingredient in marijuana, which acts on the brain to produce its effects.
Symptoms that occur after use of a drug is reduced or stopped.
Page Source: The National Institute on Drug Abuse
U.S. Department of Health and Human Services.
and Medical Marijuana Effects
The History of Opium