Brain Health

Marijuana use directly affects brain function — specifically the parts of the brain responsible for memory, learning, attention, decision-making, coordination, emotions, and reaction time. 1,2

What are the short-term effects of marijuana on the brain?

Recent marijuana use (defined as within 24 hours) in youth and adults has an immediate impact on thinking, attention, memory, coordination, movement, and time perception.1

What are the long-term effects of marijuana on the brain?

Marijuana affects brain development. Developing brains, such as those in babies, children, and teenagers, are especially susceptible to the harmful effects of marijuana and tetrahydrocannabinol (THC).1,2 Although scientists are still learning about the effects of marijuana on developing brains, studies suggest that marijuana use by mothers during pregnancy could be linked to problems with attention, memory, problem-solving skills, and behavior in their children.3-9

Using marijuana before age 18 may affect how the brain builds connections for functions like attention, memory, and learning.10 Marijuana’s effects on attention, memory, and learning may last a long time or even be permanent,11 but more research is needed to fully understand these effects. Youth who use marijuana may not do as well in school and may have trouble remembering things.1,6,12,13

The impact of marijuana use on the brain depends on many factors, including:

• Amount of tetrahydrocannabinol (THC) in marijuana (in other words, the concentration or strength),
• How often it is used,
• Age of first use, and
• Whether other substances (for example, tobacco and alcohol) are used at the same time.

Long-term impacts on the brain may also be caused by something other than marijuana, such as genetics, the home environment, or other unknown factors.14 The National Institute on Drug Abuse is conducting a large long-term study (the Adolescent Brain Cognitive Development studyexternal icon, or ABCD study) to better understand the role marijuana and other substances play in adolescent brain development.

  1. National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington, DC: The National Academies Press; 2017.
  2. Batalla A, Bhattacharyya S, Yuecel M, et al. Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings. PloS One. 2013;8(2):e55821.
  3. Grewen K, Salzwedel AP, Gao W. Functional Connectivity Disruption in Neonates with Prenatal Marijuana Exposureexternal icon. Frontiers in Human Neuroscience9, 601.
  4. Goldschmidt L, Day NL, Richardson GA. Effects of prenatal marijuana exposure on child behavior problems at age 10. Neurotoxicology and Teratology. 2000;22(3):325-336.
  5. Leech S, Richardson GA, Goldschmidt L, Day NL. Prenatal substance exposure: effects on attention and impulsivity of 6-year-olds. Neurotoxicology and Teratology. 1999;21(2):109-118.
  6. Goldschmidt L, Day NL, Richardson GA. Effects of prenatal marijuana exposure on child behavior problems at age 10. Neurotoxicology and Teratology. 2000;22(3):325-336.
  7. Fried PA, Watkinson B, Gray R. Differential effects on cognitive functioning in 9-to 12-year olds prenatally exposed to cigarettes and marihuana. Neurotoxicology and Teratology. 1998;20(3):293-306.
  8. El Marroun H, Hudziak JJ, Tiemeier H, et al. Intrauterine cannabis exposure leads to more aggressive behavior and attention problems in 18-month-old girls. Drug and Alcohol Dependence. 2011;118(2-3):470-474.
  9. Ryan SA, Ammerman SD, O’Connor ME. Marijuana use during pregnancy and breastfeeding: implications for neonatal and childhood outcomes. Pediatrics. 2018;142(3).
  10. S. Department of Health and Human Services. National Institutes of Health. National Institute on Drug Abuse. Retrieved from: https://www.drugabuse.gov/drug-topics/marijuanaexternal icon.
  11. Meier MH, Caspi A, Ambler A, et al. Persistent cannabis users show neuropsychological decline from childhood to midlife. Proceedings of the National Academy of Sciences. 2012;109(40):E2657-E2664.
  12. National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington, DC: The National Academies Press; 2017.
  13. Filbey FM, Aslan S, Calhoun VD, et al. Long-term effects of marijuana use on the brain. Proceedings of the National Academy of Sciences. 2014;111(47):16913-16918.
  14. Jackson NJ, Isen JD, Khoddam R, et al. Impact of adolescent marijuana use on intelligence: Results from two longitudinal twin studies. Proceedings of the National Academy of Sciences. 2016;113(5):E500-E508.