LOS ANGELES, California (Reuters) -- Marijuana smoking does not increase a person's risk of developing lung cancer, according to the findings of a new study at the University of California Los Angeles that surprised even the researchers.
They had expected to find that a history of heavy marijuana use, like cigarette smoking, would increase the risk of cancer.
Instead, the study, which compared the lifestyles of 611 Los Angeles County lung cancer patients and 601 patients with head and neck cancers with those of 1,040 people without cancer, found no elevated cancer risk for even the heaviest pot smokers. It did find a 20-fold increased risk of lung cancer in people who smoked two or more packs of cigarettes a day.
The study results were presented in San Diego Tuesday at a meeting of the American Thoracic Society.
The study was confined to people under age 60 since baby boomers were the most likely age group to have long-term exposure to marijuana, said Dr. Donald Tashkin, senior researcher and professor at the UCLA School of Medicine.
The results should not be taken as a blank check to smoke pot, which has been associated with problems including cognitive impairment and chronic bronchitis, said Dr. John Hansen-Flaschen, chief of pulmonary and critical care at the University of Pennsylvania Health System in Philadelphia. He was not involved in the study.
Previous studies showed marijuana tar contained about 50 percent more of the chemicals linked to lung cancer, compared with tobacco tar, Tashkin said. In addition, smoking a marijuana joint deposits four times more tar in the lungs than smoking an equivalent amount of tobacco.
"Marijuana is packed more loosely than tobacco, so there's less filtration through the rod of the cigarette, so more particles will be inhaled," Tashkin said in a statement. "And marijuana smokers typically smoke differently than tobacco smokers -- they hold their breath about four times longer, allowing more time for extra fine particles to deposit in the lung."
He theorized that tetrahydrocannabinol, or THC, a chemical in marijuana smoke that produces its psychotropic effect, may encourage aging, damaged cells to die off before they become cancerous.
Hansen-Flaschen also cautioned a cancer-marijuana link could emerge as baby boomers age and there may be smaller population groups, based on genetics or other factors, still at risk for marijuana-related cancers.
Marijuana-derived drug curbs bladder pain
Washington: The animal model study presented recently at the annual meeting of the American Urological Association showed that Ajulemic acid (IP 751), a primary synthetic analog of a metabolite of THC-the principal active component of marijuana, can effectively curb pain and bladder overactivity in hypersensitive bladder disorders such as interstitial cystitis (IC).
To conduct the study, researchers at the University of Pittsburgh School of Medicine addressed the hydrophobic properties of IP 751 by introducing the drug into a liposome, a tiny sac surrounded by fatty acids, allowing the drug to be introduced directly into the bladders of rat models of varying degrees of bladder inflammation.
IP 751 significantly overpowered bladder overactivity, both in animal models. By stopping the underlying cause of irritation - overactivity of the bladder - the drug is able to eliminate the associated pain.
According to the National Institute of Diabetes and Digestive and Kidney Diseases, 700,000 Americans have IC; 90 percent are women. IC is one of the chronic pelvic pain disorders, defined by recurring discomfort or pain in the bladder and surrounding pelvic region.
The symptoms of the disease may vary and can include any combination of mild to severe pain, pressure and tenderness in the bladder and pelvic area and there could be an urgency or necessity to urinate. In IC, the bladder wall may become scarred or irritated, and pinpoint bleeding may appear on the bladder wall.
The disease prior to the research did not have any substantial and effective treatment.
"Interstitial cystitis is a difficult disease to treat, and not all treatments work well on all patients," said Michael B. Chancellor, M.D., professor of urology and gynecology at the University of Pittsburgh School of Medicine.
The findings are supposed to be a boon to various bladder diseases.
"Any new option we can give our patients to alleviate their painful symptoms is very important," added the Chancellor of the University.
Indevus Pharmaceuticals Inc., a biopharmaceutical company had sponsored the study and the results have been published in abstract 25.
The NIH and the Fishbein Family Foundation Center of Urologic Research Excellence - Interstitial Cystitis (CURE-IC) Project, have also supported the study.