What We Know about the Impact of Marijuana on Children

Adults who first used marijuana at or before age 14 are six times more likely to abuse or be addicted to the drug than those who first started using at age 18 or older, according to the 2009 National Survey on Drug Use and Health, as presented in a CESAR Fax.

The California Society of Addiction Medicine says that marijuana is addictive to:

  • 9 percent of people who have ever used the drug, starting at age 18 or older.
  • This triples among those who ever used the drug and started before age 18.
  • 35 to 40 percent of people who use the drug daily.

The Lancet published a review of the scientific literature over the past decade. Findings are quoted here:

Acute Adverse Effects of Marijuana

  • Anxiety and panic, especially in naive users
  • Psychotic symptoms (at high doses)
  • Road crashes if a person drives while intoxicated

Chronic Adverse Effects of Marijuana

  • Cannabis dependence syndrome (in around one in ten users)
  • Chronic bronchitis and impaired respiratory function in regular smokers
  • Psychotic symptoms and disorders in heavy users, especially those with a history of psychotic symptoms or a family history of these disorders
  • Impaired educational attainment in adolescents who are regular users
  • Subtle cognitive impairment in those who are daily users for 10 years or more

Possible Adverse Effects of Regular Cannabis (Marijuana) Use with Unknown Causal Relation

  • Respiratory cancers
  • Behavioural disorders in children whose mothers used cannabis while pregnant
  • Depressive disorders, mania, and suicide
  • Use of other illicit drugs by adolescents

The National Institute on Drug Abuse funds some 80 percent of the world’s research on the impact of addictive drugs on the brain and body. The Institute summarizes what is know in this Research Report.


Copyright 2011 by National Families in Action. All rights reserved. Last updated: