5) OOPS, MARIJUANA MAY PREVENT CANCER (PART I): Federal researchers implanted several types of cancer, including leukemia and lung cancers, in mice, then treated them with cannabinoids (unique, active components found in marijuana). THC and other cannabinoids shrank tumors and increased the miceâ€™s lifespans. Munson, AE et al. Antineoplastic Activity of Cannabinoids. Journal of the National Cancer Institute. Sept. 1975. p. 597-602.