Does smoking marijuana contribute to the risk of developing lung cancer?

Different concentrations of THC stimulate formation of reactive oxygen species in cells that are exposed to smoke from the distal end of the “joint,” indicating that cell damage is caused by toxic gas in the smoke. Lung cancer has emerged as the most common cause of cancer-related death in men and women in the United States (Edmondson, 2008; Swaney, 2002). Marijuana, a product of the Cannabis sativa plant, is the most frequently used illegal substance in the United States (Mehra, Moore, Crothers, Tetrauld, & Fiellin, 2006). The question explored here is whether evidence links marijuana use to lung cancer development. Tobacco use was known to Native Americans, but the first recorded harvest of a tobacco crop in North America was in 1611 in the Jamestown colony (Cruz et al., 1998). Marijuana has a world history that dates back to 4000 BC, when it was grown in China for the hemp fibers. Oral traditions from China list medical uses for marijuana as far back as 2700 BC (Zuardi, 2005). Marijuana use in the United States dates to the early 1900s, when it was used as a cure for morphine addiction (Cruz et al., 1998). Marijuana primarily is obtained from the leaves and flower heads of the female Cannabis sativa plant. The active ingredient is delta-9 tetrahydrocannabinol (THC), with the highest content found in the flower heads and decreasing in concentration from the stems down to the seeds (Campbell, 1999; Hall & Solowij, 1998).