Immunity to Disease

In May 1973, The New York Times published a long letter to the editor by Dr. Gabriel Nahas of Columbia University's College of Physicians and Surgeons, claiming that marijuana interferes with the ability of the white blood cells in the human body to fight disease. The research of Nahas and his associates was published the following year in the February 1974 issue of Science. In a complex series of laboratory procedures, Nahas claimed to prove that marijuana smokers lacked an essential means of defense against infectious diseases and cancer. In October 1974, a similar report appeared in the New England Journal of Medicine, and before long, laboratories across North America were discovering a weakened immunity response in cultured cells that had been exposed to very potent solutions of marijuana.
    Critics argue that the evidence suggesting a link between cannabis and the impairment of immune response is usually derived from test-tube research and has not been confirmed by experiments on live subjects. A study of marijuana use in Costa Rica found no evidence of weakened immunity among long-term smokers. And Dr. Melvin J. Silverstein of UCLA, who tested marijuana smokers by directly injecting foreign antibodies into their skin, showed that the immunity response of a group of twenty-two marijuana smokers was healthy and normal. A study published in the April 1975 issue of Science by S. C. White and his associates also found no evidence to support Nahas's contentions. And finally, the thirty long-term smokers examined in the Jamaica study showed no greater history of infection than did the nonsmoking members of the control group; in fact, they showed no signs of ill health related to their use of marijuana.