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IACM-Bulletin of January 15, 2012


Science — Cannabis smoking does not impair lung function according to large long-term study

Cannabis does not impair lung function - at least not in the doses inhaled by the majority of users, according to the largest and longest study ever to consider the issue, which was published in the Journal of the American Medical Association. US researchers conducted a longitudinal study collecting repeated measurements of pulmonary function and smoking over 20 years from 1985 to 2006 in 5115 men and women. "Occasional and low cumulative marijuana use was not associated with adverse effects on pulmonary function," authors summarized the results. Lifetime exposure to cannabis cigarettes was expressed in joint-years, with 1 joint-year of exposure equivalent to smoking 365 joints (cannabis cigarettes) or filled pipe bowls.

Researchers found that measures of lung function - forced expiratory volume in the first second of expiration and forced vital capacity - actually improved slightly as young people reported using more cannabis - at least up to 7 joint-years or 2,555 joints. "There's no doubt marijuana triggers a cough," said Dr. Stefan Kertesz, from the University of Alabama at Birmingham, who worked on the new study. But questions have remained about the drug's longer-term effect on lung functioning. Not surprisingly tobacco use was associated with decreased lung function. But at least at moderate levels of cannabis smoking, that didn't seem to be the case - in fact, the trend was reversed. Lung volume and air flow rates both increased with each joint-year in moderate users. "It's a very real increase (...) but it's so small that I don't think that a person would feel a benefit in terms of their breathing," Kertesz said. At the highest levels of cannabis smoking lung function seemed to decline again, but the researchers noted that there weren't enough heavy cannabis users in their study population to be sure of that.

It is unlikely that cannabis puts users at risk of chronic obstructive pulmonary disease, or COPD, as smoking tobacco does, says Dr. Donald Tashkin, professor at the University of California in Los Angeles, who studies the effects of cannabis on the lungs for decades but wasn't involved in the new study. When it comes to diminished lung function, "This particular potential complication of marijuana smoking doesn't appear to be an important risk," he told the press agency Reuters. "Therefore, people who are using marijuana for medicinal purposes or recreationally at least could be reassured that they're not harming their lungs in this way."

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(Source: Pletcher MJ, Vittinghoff E, Kalhan R, Richman J, Safford M, Sidney S, Lin F, Kertesz S. Association between marijuana exposure and pulmonary function over 20 years. JAMA 2012;307(2):173-81.)

Science — Cannabis use was not associated with cognitive impairment in people at the age of 50 according to a large epidemiological study

Researchers at King's College in London, UK, investigated the association between illicit drug use and cognitive functioning during the mid-adult years. They found that "at the population level, it does not appear that current illicit drug use is associated with impaired cognitive functioning in early middle age." A total of 8,992 participants who were surveyed at 42 years of age in the years 1999 and 2000 were included. The authors analyzed data on 3 cognition tests when the participants were 50 years of age in the years 2008 and 2009.

Cannabis was by far the most common used drug of the participants with six percent saying they had used it in the past year, while one-quarter said they had ever used it. Overall, the study found, there was no evidence that current or past drug users had poorer mental performance. In fact, when current and past users were analysed together, their test scores tended to be higher. But that advantage was small, the researchers said, and might just reflect another finding - that people who'd ever used drugs generally had a higher education level than non-users. "However, the authors cannot exclude the possibility that some individuals and groups, such as those with heavier or more prolonged use, could be harmed," they write in their article for the American Journal of Epidemiology.

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(Source: Dregan A, Gulliford MC. Is Illicit Drug Use Harmful to Cognitive Functioning in the Midadult Years? A Cohort-based Investigation. Am J Epidemiol. 2011 Dec 21. [in press])

Science — Cannabis-ketamine synergy in intractable neuropathic pain in case report

Two doctors from the Institute for Neuropathic Pain in Soest, The Netherlands, reported of a 56 year old woman suffering from severe chronic neuropathic pain due to damage of the right ulnar nerve. During her life she had had several fractures and surgeries of her right arm. Since 1996 she suffers from pain in the innervation area of the ulnar nerve, which is mainly the area of the fourth and fifth finger. The pain increased in the following years with a pain intensity of 7 on an 11-point numerical rating scale (NRS) with "0=no pain" and "10=highest possible pain," despite the use of opiates and other pain medication.

She stopped the medication due to severe side effects and started using oral cannabis (0.5 grams per day in cookies) resulting in the reduction of pain intensity from 8 to 5 on the pain scale. Adding ketamine cream twice daily further reduced the pain (pain scale: 2 to 3). Ketamine is a medicinal drug used for general anaesthesia and also for pain reduction. Authors concluded: "Ketamine and cannabis may act synergistically because cross-talk exists and the cannabinoid and the opioid receptor systems also have synergistic interactions."

(Source: Hesselink JM, Kopsky DJ. Intractable neuropathic pain due to ulnar nerve entrapment treated with cannabis and ketamine 10% J Clin Anesth. 2012 Jan 5. [in press])

News in brief

Science — Cannabis increases creativity in people with low creativity

According to research of the University College London, UK, with 160 cannabis users, who were investigated one day under the influence of cannabis and one day sober, cannabis influenced psychosis-like symptoms and verbal fluency as a measure of creativity. Subjects were divided into four groups of creativity level. The drug increased psychosis-like symptoms in people with the highest and lowest creativity. In addition, acute cannabis use increased creativity in people with low creativity. (Source: Schafer G, et al. Conscious Cogn. 2012 Jan 7. [in press])

Science — THC neuroprotective in model of Parkinson's disease

Researchers of the University of Plymouth, UK, demonstrated an increase of the CB1 receptor in direct response to neuronal injury in a cell culture model of Parkinson's disease, and a direct protective effect of THC on the nerves. (Source: Carroll CB, et al. Neuropathol Appl Neurobiol. 2012 Jan 11. [in press])

Science — Pharmacokinetics of Namisol (THC)

The pharmaceutical company Echo Pharmaceuticals in Nijmegen, The Netherlands, investigated the pharmacokinetic properties of their THC preparation Namisol. Namisol is a new tablet containing THC designed to improve bioavailability. Oral Namisol resulted in a maximum blood concentration after 39-56 minutes. Authors noted that "variability and the time of maximum value of THC plasma concentrations were smaller for Namisol than reported for studies using oral dronabinol and nabilone." (Source: Klumpers LE, et al. Br J Clin Pharmacol. 2011 Dec 28. [in press])

Science — Nabilone did not reduce experimental acute pain in clinical study

Researchers of the pharmaceutical AstraZeneca investigated the effects of the synthetic cannabinoid nabilone on acute pain, which was induced by a chemical (capsaicin), in a placebo-controlled cross-over study with 30 healthy subjects. The cannabinoid had no significant effect on acute pain. (Source: Kalliomäki J, et al. Clin Exp Pharmacol Physiol. 2012 Jan 10. [in press])

Science — Endocannabinoids reduce allergic reactions in the skin in tissue experiments

Researchers from University of Lübeck, German, investigated the effects of the stimulation of CB1 receptors on so-called mast cells in human skin. These cells are important for allergic reactions. Researchers found that mast cells in normal skin are controlled by the endocannabinoid system limiting excessive activation of mast cells. They concluded that "CB1 stimulation is a promising strategy for the future management of allergy." (Source: Sugawara K, et al. J Allergy Clin Immunol. 2012 Jan 6. [in press])