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Comments and Controversies

Substance abuse clarifications

Vol. 9, No. 11 / November 2010

How to manage medical complications of the 5 most abused substances” (Current Psychiatry, November 2009, p. 35-47) contains several errors of fact, emphasis, and inappropriate citation of references that may mislead readers.

The article states “marijuana use can double or triple the risk of cancer of the respiratory tract and lungs” and cites a reference by Tashkin et al.1 In fact, that review article states “…evidence that marijuana smoking may lead to…respiratory cancer is limited and inconsistent.” A subsequent case-control study by Tashkin and colleagues found no increased risk of lung or upper respiratory tract cancer among heavy marijuana smokers.2 A smaller case-control study from New Zealand did find an 8% increased risk of lung cancer associated with each joint-year of marijuana smoking.3 However, the Current Psychiatry article grossly exaggerated the cancer risk from marijuana smoking and cited an inappropriate supporting reference.

The article states that “growing evidence shows that marijuana use could lead to cardiac arrhythmias, such as atrial fibrillation” and cites 1 supporting reference.4 That article reviewed the 6 published cases of atrial fibrillation (AF) associated with marijuana smoking and acknowledged “the exact incidence of AF related to marijuana smoking is difficult to be estimated.” Other reviews of the cardiovascular effects of marijuana smoking take a broader view, eg, “marijuana’s cardiovascular effects are not associated with serious health problems for most young, healthy users.”5 Given the ratio between 6 published case reports and the millions of people smoking marijuana daily, this may be a more appropriate perspective for a review article.

The article states “some studies show persistent cognitive impairments in longer term cannabis users, even after 2 years of abstinence” and cites 1 supporting reference by Pope et al6 (incorrectly cited as Harrison et al). In fact, that study did not test subjects beyond 28 days of abstinence; at the time, “the differences between users and controls had narrowed and were mostly nonsignificant.” Other studies have found no significant differences between marijuana smokers and non-users after 3 months of abstinence,7 nor are significant long-term cognitive deficits mentioned in recent reviews of the topic.8 Thus, we are not aware of any scientific basis for the statement in the article, which is not supported by the 1 study cited.

The paragraph on “cardiac complications” of cocaine use presents an incomplete picture of the risk of myocardial infarction (MI) and cites only 1 (2001) review article. What would have been useful to the reader was:

  • cocaine-associated MI occurs in up to 6% of patients with cocaine-associated chest pain9
  • cocaine-associated MI may have atypical symptomatic presentation, eg, without chest pain9
  • in a large, population-based study, adults age 18 to 45 who used cocaine >10 times had a 3.5-fold increased risk of MI10
  • two-thirds of MIs occur within 3 hours of cocaine ingestion, but MI may occur >18 hours after ingestion (possibly due to pharmacologically active cocaine metabolites).9 The recent review by McCord et al,9 which includes treatment recommendations from the American Heart Association, would have been useful to cite.

Most readers of Current Psychiatry are not specialists in the topics covered by its review articles. This places increased responsibility for ensuring accurate and balanced topic coverage with citation of appropriate, up-to-date review articles.

David A. Gorelick, MD, PhD
National Institute on Drug Abuse
Baltimore, MD


1. Tashkin DP. Smoked marijuana as a cause of lung injury. Monaldi Arch Chest Dis. 2005;63(2):93-100.

2. Hashibe M, Morgenstern H, Cui Y, et al. Marijuana use and the risk of lung and upper aerodigestive tract cancers: results of a population-based case-control study. Cancer Epidemiol Biomarkers Prev. 2006;15(10):1829-1834.

3. Aldington S, Harwood M, Cox B, et al. Cannabis use and risk of lung cancer: a case-control study. Eur Respir J. 2008;31(2):280-286.

4. Korantzopoulos P, Liu T, Papaioannides D, et al. Atrial fibrillation and marijuana smoking. Int J Clin Pract. 2008;62(2):308-313.

5. Jones RT. Cardiovascular system effects of marijuana. J Clin Pharmacol. 2002;42(11 suppl):58S-63S.

6. Pope HG, Jr, Gruber AJ, Hudson JI, et al. Cognitive measures in long-term cannabis users. J Clin Pharmacol. 2002;42(11 suppl):41S-47S.

7. Fried PA, Watkinson B, Gray R. Neurocognitive consequences of marihuana—a comparison with pre-drug performance. Neurotoxicol Teratol. 2005;27(2):231-239.

8. Schweinsburg AD, Brown SA, Tapert SF. The influence of marijuana use on neurocognitive functioning in adolescents. Curr Drug Abuse Rev. 2008;1(1):99-111.

9. McCord J, Jneid H, Hollander JE, et al. Management of cocaine-associated chest pain and myocardial infarction: a scientific statement from the American Heart Association Acute Cardiac Care Committee of the Council on Clinical Cardiology. Circulation. 2008;117(14):1897-1907.

10. Aslibekyan S, Levitan EB, Mittleman MA. Prevalent cocaine use and myocardial infarction. Am J Cardiol. 2008;102(8):966-969.

The authors respond

Dr. Gorelick’s detailed comments brought up many points, which we address below.

Marijuana and cancer—Dr. Gorelick commented that the article “grossly exaggerated the cancer risk from marijuana smoking” due to the cited reference stating that the evidence is “limited and inconsistent.” We agree the article mentions the evidence is not clear. However, in further reading of their discussion of the risk of lung cancer the authors point to several epidemiologic studies, some of which showed increased risk of cancer. Specifically, a study from the United States showed “a history of daily or near-daily marijuana smoking was associated with a 2.6-fold greater risk for developing head and neck cancer.”

In our article we focused more on the positive results than on the entire picture and would have served our readers better by not making such an equivocal statement about the increased risk of cancer.

Marijuana and AF—Dr. Gorelick questioned the tenacity of the association between marijuana and AF, stating “given the ratio between 6 published cases reports and the millions of people smoking marijuana daily, this may be a more appropriate perspective for a review article.”

Our comments were based on the following statements from the cited study: “During the past few years an increasing number of case reports indicate an association between marijuana smoking and the development of AF.” Also, “despite the small number of these reports, the observed close temporal relationship between marijuana smoking and AF occurrence, especially in young people without structural heart disease or other precipitating factors for AF, strongly supports an association between the two conditions.”

We mentioned AF because this is not something most people consider as a side effect of marijuana and we felt it was useful to call attention to it as a potential complication. However, we do agree that the sentence could have been worded differently because the number of cases remains low and the risk of developing AF in young healthy adults is low.

Marijuana and cognitive effects—Dr. Gorelick commented that there is “no scientific basis for the statement in the article” and that the article cited looked only at 28 days post-cannabis use. The following comments were made in the article we cited: “However, one electroencephalographic study suggested greater abnormalities in longer term cannabis users, and another found a strong correlation between performance on a selective attention task and duration of cannabis use, even in users abstinent for a mean of 2 years.”

Also, that article concluded “…an opposite impression emerges from a recent large, carefully controlled study by Solowij et al, who found that longer term cannabis users showed significantly greater deficits on several neuropsychological measures than shorter term users, and that these measures were often negatively correlated with lifetime duration of use.”

Again, we agree that our comment was likely too broad because the evidence is limited and not clear, which is why we wrote, “However, most studies suggest that marijuana-associated cognitive deficits are reversible and related to recent exposure.”

Cocaine and cardiac complications—We thank Dr. Gorelick for providing additional information and resources about the very important association between cocaine use and the MI risk. We certainly agree that the inclusion of his suggested references would have been appropriate.

Raheel Khan, DO
Assistant Clinical Professor
Psychosomatic Medicine
Department of Psychiatry and Behavioral Sciences

Robert M. McCarron, DO
Training Director, Internal Medicine/Psychiatry Residency
Department of Psychiatry and Behavioral Sciences
Department of Internal Medicine
University of California, Davis
Sacramento, CA

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