The link between cannabis use and cognitive functioning has captivated scientists and the public. In this section, we present our original study followed by a commentary on the study, some letters to the editor, and two subsequent studies. In addition, we provide links to media coverage, most of which is serious and some of which is funny. Collectively, these readings lay out some of the concerns and controversies in this area of research. These readings can be packaged together for teaching purposes.
- Meier MH, Caspi A, Ambler A, Harrington HL, Houts R, Keefe RSE, McDonald K, Ward A, Poulton R, Moffitt TE Persistent cannabis users show neuropsychological decline from childhood to midlife. 2012 Proceedings of the National Academy of Sciences Plus 109:2657-2664
- Gonzalez R. Swanson JM. (2012) Long term effects of adolescent onset and persistent use of cannabis. PNAS 109: 5970–15971, www.pnas.org/cgi/doi/10.1073/pnas.121412410915970–15971
Letters to the Editor
- Rogeberg O (2013) Correlations between cannabis use and IQ change in the Dunedin cohort are consistent with confounding from socioeconomic status. PNAS, 110:4251-4254.
- Daly M (2013) Personality may explain the association between cannabis use and neuropsychological impairment. PNAS, 110:E979
- Moffitt TE, Meier MH, Poulton R, Caspi A. (2013). Reply to Rogeberg and Daly: No evidence that socioeconomic status or personality differences confound the association between cannabis use and IQ decline. PNAS, 110:E980-2
Subsequent, Independent Reports about the Link between Cannabis Use and Neuropsychological Decline
It is instructive to read Meier et al. alongside these articles, and to compare and contrast the approaches and conclusions
- Meier et al. (2022). Long-term cannabis use and cognitive reserves and hippocampal volume in midlife. Am J Psychiatry, 179:362-374
- Schaefer et al. (2021). Associations between adolescent cannabis use and young-adult functioning in three longitudinal twin studies. PNAS, 118:E201318018
- Ross et al. (2020). Investigating the causal effect of cannabis use on cognitive function with a quasi-experimental co-twin design. Drug Alcohol Depend 2020; 206:107712
- Meier et al. (2017). Associations between adolescent cannabis use and neuropsychological decline: a longitudinal co-twin control study. Addiction, 113:257-265.
- Jackson NJ et al. (2016). Impact of adolescent marijuana use on intelligence: Results from two longitudinal twin studies. PNAS, 113: E500-508.
- Auer R et al. (2016). Association Between Lifetime Marijuana Use and Cognitive Function in Middle Age: The Coronary Artery Risk Development in Young Adults (CARDIA) Study. JAMA: Internal Medicine, February 01, 2016. doi:10.1001/jamainternmed.2015.7841
- Hall W. Lynskey M. (2016). Long-term Marijuana Use and Cognitive Impairment in Middle Age. JAMA: Internal Medicine, February 01, 2016. doi:10.1001/jamainternmed.2015.7850
- Weed users found to have poorer verbal memory in middle age. (CNN, Feb. 10, 2016)
- What happens when you get stoned every single day for five years. (The Washington Post, Feb. 1, 2016)
- Does cannabis really lower your IQ? (The Guardian, Jan. 14, 2016)
- What Science Says About Marijuana. (The New York Times, July 30, 2014)
- Marijuana May Hurt The Developing Brain. (NPR, March 3, 2014)
- Ruth Marcus: The perils of legalized pot. (The Washington Post, Jan. 2, 2014)
- Weed: Been There. Done That. (The New York Times, Jan. 2, 2014)
- Early-Onset, Regular Cannabis Use Is Linked to IQ Decline. (National Institute on Drug Abuse, Aug. 13, 2013)
- Message from the Director: Marijuana's Lasting Effects on the Brain. (National Institute on Drug Abuse, March 2013)
- Teen cannabis use lowers IQ, despite claims to the contrary. (The Conversation, Jan. 14, 2013)
- Duh! 12 Obvious Science Findings of 2012. (LiveScience, Dec. 26, 2012)
- Can Smoking Marijuana Actually Lower Your IQ? (NIDA, Oct. 9, 2012)
- Drop in IQ linked to heavy teenage cannabis use. (Nature, Aug. 28, 2012)
Just google 'cannabis' and 'IQ', and open your mind to the blogosphere. Or compare contrasting positions by visiting https://learnaboutsam.org/
The Potency of Cannabis
- Changes in Cannabis Potency over the Last Two Decades (1995-2014) — Analysis of Current Data in the United States. Mahmoud A. ElSohly Ph.D., Zlatko Mehmedic M. Sc.Pharm., Susan Foster B.A., Chandrani Gon M.Sc.Botany, Suman Chandra Ph.D., James C. Church Ph.D.
2016 NIH Marijuana and Cannabinoid Conference
This conference features many informative presentations. Madeline Meier also speaks about the cannabis-IQ link on Day 1, at 2 hours and 36 minutes.