“Besides being addictive, marijuana is cognitively impairing even beyond the phase of acute intoxication and regular use during adolescence may cause a significant, possibly permanent IQ loss. Brain scans in users who started when they were young show impaired neural development, probably because cannabis interferes with normal brain maturation.” —Nora Volkow, MD, Director, National Institute of Drug Abuse, National Institute of Health
Scientists from the National Institute of Drug Abuse published these facts on the negative health effects of short-term and long-term use of marijuana.
Source: Nora D. Volkow, MD, Ruben D. Baler, PhD, Wilson M. Compton, MD, and Susan R.B. Weiss, PhD, N Engl J Med 2014; 370:2219-2227 June 5, 2014 DOI: 10.1056/NEJMra1402309.
The new concern with marijuana are edible marijuana products which may produce serious physical side effects to both adults and teens. They may ingest high amounts of THC in the marijuana edible product and not know it. Eating a cookie with marijuana may not produce the quick "high" that the user has when smoking marijuana, so that he may continue to eat more in a short time ingesting large amounts of THC. Many food products do not include specific labels on the marijuana content or warnings on possible serious side effects.