The use of marijuana can produce adverse physical, mental, emotional, and behavioral changes, and - contrary to popular belief - it can be addictive. Marijuana smoke, like cigarette smoke, can harm the lungs.4,5,6 The use of marijuana can impair short-term memory,7,8 verbal skills,9 and judgment10 and distort perception.11,12 It also may weaken the immune system13,14,15,16 and possibly increase a user's likelihood of developing cancer.14,17 Finally, the increasing use of marijuana by very young teens may have a profoundly negative effect upon their development.9, 18, 19,20 Nora D. Volkow, M.D.


A study of 15 heavy pot smokers published in June 2008 in the Archives of General Psycharity showed loss of tissue in two areas of the brain, the hippocampus and amygdala, regions that are rich in receptors for marijuana and that are important for memory and emotions.

In addition, in a recent study by the Mayo Clinic, THC was shown to be less effective than standard treatments in helping cancer patients regain lost appetites.10 10"Marijuana Appetite Boost Lacking in Cancer Study" The New York Times, May 13, 2001.

Any determination of a drug's valid medical use must be based on the best available science undertaken by medical professionals. The Institute of Medicine conducted a comprehensive study in 1999 to assess the potential health benefits of marijuana and its constituent cannabinoids. The study concluded that smoking marijuana is not recommended for the treatment of any disease condition. In addition, there are more effective medications currently available. For those reasons, the Institute of Medicine concluded that there is little future in smoked marijuana as a medically approved medication.8 8"Marijuana and Medicine: Assessing the Science Base," Institute of Medicine, 1999.

LONDON — New findings on marijuana's damaging effect on the brain show the drug triggers temporary psychotic symptoms in some people, including hallucinations and paranoid delusions, doctors say. British doctors took brain scans of 15 healthy volunteers given small doses of two of the active ingredients of cannabis, as well as a placebo. The results, to be presented at an international mental health conference in London on Tuesday and Wednesday, provides physical evidence of the drug's damaging influence on the human brain.

In analyzing MRI scans of the study's subjects, McGuire and his colleagues found that THC interfered with activity in the inferior frontal cortex, a