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'''Cannabis-associated respiratory disease''' can refer to ] or to structural damage to the ].{{Citation needed|date=May 2013}} |
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It is often compared to the damage done by ], but it is the subject of much less study. ] is sometimes considered more dangerous because filters are usually not used, and sometimes considered less dangerous because different molecules are involved.{{Citation needed|date=May 2013}} |
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The process most popularly used to ingest cannabis is smoking, and for this reason most research has evaluated health effects from this method of ingestion. Other methods of ingestion may have lower or higher health risks. Tobacco smoking has well-established risks such as ], ]ing, overproduction of ], ], and ]. Similar risks for smoking cannabis related to airway ] have been suggested in a 1998 study of 40 healthy cannabis users who exhibited similar early characteristics to ].<ref>http://www.ncbi.nlm.nih.gov/pubmed/9517614</ref> |
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The effects of tobacco and cannabis smoking differ, however, as they affect different parts of the ]: whereas tobacco tends to penetrate to the smaller, peripheral passageways of the ], cannabis tends to concentrate on the larger, central passageways. One consequence of this is that cannabis, unlike tobacco, has not been shown to cause ], though this claim is disputed by Martin Johnson, MD, of the department of respiratory medicine at Glasgow (Scotland) Royal Infirmary <ref>http://www.webmd.com/lung/copd/news/20000320/regular-marijuana-emphysema</ref>. A 2002 report by the ] estimated that three to four cannabis cigarettes a day were associated with the same amount of damage to the lungs as 20 or more tobacco cigarettes a day.<ref>{{dead link|date=January 2013}}</ref> Unlike tobacco, regular cannabis use does not appear to cause ].<ref>{{cite journal |author=Tashkin DP, Simmons MS, Sherrill DL, Coulson AH |title=Heavy habitual marijuana smoking does not cause an accelerated decline in FEV1 with age |journal=American Journal of Respiratory and Critical Care Medicine |volume=155 |issue=1 |pages=141–8 |year=1997 |month=January |pmid=9001303 |doi=10.1136/thx.2006.077081}}</ref> |
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In some cases, cannabis users mix commercial tobacco in ], called "Spliff" (popular in Europe), tobacco mixed with hash in a ] (India), or cannabis rolled in tobacco leaves (a ]), which would expose the user to the additional risks of tobacco, such as rapid physical addiction to ].<ref name="groups.psychology.org.au">, page 4. "Cannabis has been described as a 'Trojan Horse' for nicotine addiction, given the usual method of mixing cannabis with tobacco when preparing marijuana for administration."</ref> |
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== UCLA study == |
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== UCLA study == |
On 23 May 2006, Donald Tashkin, M.D., Professor of Medicine at the David Geffen School of Medicine at UCLA in Los Angeles announced that the use of cannabis does not appear to increase the risk of developing lung cancer, or increase the risk of head and neck cancers, such as cancer of the tongue, mouth, throat, or esophagus. The study involved 2252 participants, with some of the most chronic marijuana smokers having smoked over 22,000 marijuana cigarettes. The finding of Donald Tashkin, M.D., and his team of researchers in 2006 refined their earlier studies published in a Dec. 17th 2000 edition of the peer-reviewed journal Cancer Epidemiology Biomarker and Prevention. Many opponents of marijuana incorrectly cite the original finding of UCLA Medical Center from 2000 as "proof" that marijuana leaves the users at higher risk for cancer of the lung, and cancerous tumors, even though the researchers at the UCLA Medical Center have revised their finding with a more in-depth study on the effects of the use of marijuana. This seemed to contradict assumptions made after some studies, like those from Dale Gieringer et al., which found that 118 carcinogens were produced when marijuana underwent combustion, and two carcinogens {2-Methyl-2, 4(2H-1-benzopyran-5-ol) & 5-azulene-3,8-dione} formed when marijuana underwent vaporization with the Volcano Vaporizer. To help explain this seemingly chemical proof of carcinogenicity inherent in the process of combustion, Tashkin noted that "one possible explanation for the new findings, he said, is that THC, a chemical in marijuana smoke, may encourage aging cells to die earlier and therefore be less likely to undergo cancerous transformation."
In a study of ten smokers with mild respiratory issues Hii et al. found evidence of lung disease in the form of severe bullae (fluid-filled, thin-walled blisters) of different shapes and sizes. Despite such lung disease, the patients' chest x-rays were normal and lung function was only mildly reduced in nearly half of the patients. The cannabis-smoking patient group was, on average, 41 years old—considerably younger than previously research tobacco-smoking patients with lung disease, who had an average age of between 62–67 years. The researchers conclude that the younger age of lung disease and poorer lung function may be due to different smoking patterns demonstrated in cannabis smokers, who have been found to inhale larger amounts of smoke, which is held in the lungs for longer periods of time.
