Setting the Record Straight
Cannabis research is not legal in many parts of the world
Unfortunately for the journalists who wrote those articles and for the author of the study Dr. Wayne Hall, the existing body of cannabis research including Dr. Hall's own studies, debunk his current findings. If you are curious how the existing body of evidence, including his previous work, can be ignored for this current study it is because this review only looked for "changes in the evidence on the adverse health effects of cannabis since 1993."
Dr. Hall has made his research bias blatantly obvious in the first line of his abstract, and made it clear that any positive changes were disregarded entirely. Aside from a heavy dose of research bias, this study suffers from repeated moments where correlation is assumed to be causation, a common mistake. Correlation simply means two things are related, such as eating ice-cream being related to higher rates of drowning. Eating ice-cream doesn't cause drowning, but going to a swimming pool where one may eat ice cream and then go swimming could cause one to drown. Simply put, correlation does not equal causation.
Before dissecting the study and debunking its major claims, some background information is needed. First, Dr. Hall only looked at recreational cannabis use in this study and did not examine medical use in any way. This is strange given that the majority of research in the past twenty years has focused on the medicinal effects of cannabis. Second, it is worth noting that a heavy user is defined by Dr. Hall as anyone who uses cannabis daily or near-daily. Another major drug studied by Dr. Hall is alcohol.
According to the CDC, a heavy alcohol user is defined as someone who consumes over 15 drinks a week (or 8 for women). With alcohol, a person can still be a daily user or a binge drinker (i.e. five drinks three nights a week) and not be considered a heavy user, yet to smoke one joint a day makes you a heavy cannabis user.
That distinction is extremely biased towards alcohol and indicative that alcohol abuse is accepted by society as normal, whereas society still views any cannabis use as aberrant. Research on cannabis needs to be weighed against this societal bias in favor of alcohol abuse. The issue of cannabis abuse is understandably a great public health concern to Dr. Hall, whose country of Australia sees 10.3% of the population regularly using cannabis. The UN World Drug Report shows that Australia is not alone. Many Western countries have high rates of cannabis use; Canada with 12.6%, America with 14%, Italy and New Zealand both with 14.6%.
Dr. Hall's past research has found that tobacco, alcohol, opiates, and cannabis are correlated with psychosis, but did not prove causality. In a 2001 study, Dr. Hall found that "cannabis was not associated with anxiety or affective disorders" but alcohol and tobacco were. A 2002 study he co-authored provides strong evidence that his current claims about schizophrenia are inaccurate; they found "cannabis use does not appear to be causally related to the incidence of schizophrenia."
Hall conducted a literature review in 2008 as a follow up to his schizophrenia research and found that expressions of schizophrenia were due to "a personal or family history" and not due to cannabis use alone. In review of Dr. Hall's past research, cannabis use is not causally linked with an increase in schizophrenia, anxiety, or affective disorders, but for people with a family history of mental illness it could be a contributing factor to expressions of mental illness.
The present study highlights nine major findings which will be assessed for accuracy. First, Dr. Hall found that it is impossible to overdose on cannabis, but the LD50 he uses is grossly inaccurate. An LD50 is the dose of a substance required to kill half a sample population. Cannabis has nearly a hundred cannabinoids and nearly as many terpenes present in it, all of which have their own LD50.
To say that someone is overdosing on cannabis is about as accurate as to say someone is overdosing on coffee. In both cases the actual cause of overdose is a chemical within the whole not the whole substance; caffeine in the case of coffee. For many cannabinoids and terpenoids the LD50 is over 3 grams of the pure chemical per kilogram of body weight, which is astronomically higher and more difficult to reach than smoking 15-70 grams of cannabis, as Dr. Hall claims in his study.
Second, the literature review found that driving while intoxicated on cannabis doubles the risk of car crash, and the risk increases substantially if the user is also drunk. As stated above, cannabis has hundreds of active chemicals; the vast majority are non-psychoactive. Presumably the study is looking only at psychoactive THC-rich cannabis, as that is what is used recreationally. Clearly, driving while intoxicated or in an altered state is not advisable and raises the risk of a crash.
A study from UC San Diego released this year found that driving with a Blood Alcohol Content (BAC) of 0.01% was associated with a 50% increase in crashes; that means driving with the legal limit of a 0.08% BAC would be closer to a 400% increase. This study provided more evidence that there is "no safe combination of drinking and driving." Drugs aren't all that impair our focus, using a cellphone while driving is as dangerous as driving drunk, and now is a factor in over a quarter of all crashes.
Third, Hall's study claims 10% of cannabis users can develop a dependence syndrome, and 1/6 of those users began using in adolescence. This claim has a truthy air about it because of its similarity to the oft-cited 9% "addiction" rate bandied about in the US - despite the fact that the 9% figure was derived using the controversial DSM-IV standard, which, as Dr. Sunil Kumar Aggarwal explains, employs methodologies which are inherently biased toward showing cannabis dependence, based on factors largely stemming from its illegality.
Dr. Hall's analysis of this cannabis research is even less robust; he uses the older (and even less credible) DSM-III standard. But even assuming his claims are correct, the rates of supposed cannabis dependence would be comparable to the percentage of Americans found to be addicted to shopping (found to be 8.9% in a 2008 study) and still far less than tobacco's and heroin's 25%, or the 15% of people who become addicted to alcohol or cocaine. Cannabis is less habit-forming than currently legal drugs like alcohol and tobacco, it also less harmful to society than the rise of prescription drug abuse.
Fourth, regular cannabis use doubles one's risk of experiencing psychotic symptoms including schizophrenia, especially if there is a family history of psychotic disorders. Research released just last month shows, for the first time, that schizophrenia is actually a cluster of eight different related genetic disorders, and about 80% of the risk factors are genetic. Another study released this year shows that having a familial history of schizophrenia is "the underlying basis for schizophrenia in cannabis users and not cannabis use by itself."
Additionally, many of the studies Dr. Hall cites are self-report studies, which can be highly inaccurate, especially when asking schizophrenics in the ER who are likely suffering from psychotic episodes. Other studies, such as Arseneault et Al did not find causality but found that cannabis use was correlated with lower rates of mental disorders than Dr. Hall claims. This finding is consistent with the current opinion held by Australia's National Cannabis Prevention and Information Center that "strong associations are often found [between cannabis and mental health symptoms] but this is not the same as a causal link." The current body of evidence is consistent that there is a correlation between cannabis use and schizophrenia but there is no causation.
Fifth, adolescents that regularly use cannabis seem more likely to use other drugs but this link doesn't appear to be causal. This association is nothing new; a correlation between cannabis use and other drug use has been known for years, and usually this association is strongest with alcohol and tobacco use. The only solid finding in the study is that tobacco use has gone down recently and while previously tobacco was the most common first drug, now cannabis use seems to come earlier. If this is evidence of anything, it is evidence that young people feel that cannabis is safer than both alcohol and tobacco, or perhaps it is merely evidence that cannabis is easier for young people to obtain.
The sixth point is that regular users of cannabis have lower educational attainment and suffer from intellectual impairments from an unknown mechanism. As with the fifth point, Dr. Hall admits that his data exhibit only a correlation and that he does not prove causation. He also recognizes several confounding variables that could be the reason for what was observed, such as a pre-existing risk of not finishing school or increased affiliation with cannabis users who reject school, or a strong desire for a premature transition to adulthood.
It seems like he is describing poverty, which numerous studies and sources show has negative impacts on personal development. When someone comes from an impoverished area with bad schools, gang problems, and broken homes, there is a higher chance of them dropping out of school and generally having lower levels of academic achievement.
The seventh point the review makes is that cannabis use may increase the risk of heart attacks. Despite making this bold claim, Dr Hall did not find any risk of increased cardiovascular issues. In fact, a different 20 year long cannabis research study from 2012 found the opposite effect, that occasional cannabis smoking was not associated with negative pulmonary function, unlike tobacco use which does significant cardio harm.
The eighth point is that the overall effects of cannabis on the lungs are unknown, but that it appears that regular cannabis smokers have a higher risk of developing bronchitis. There is compelling evidence that putting smoke in your lungs from any burning organic matter is unhealthy and could cause bronchitis, including camp fires, barbeques, and tobacco smoking. Smoke contains benzopyrene, a carcinogen found in cigarette smoke, cannabis smoke, as well as in the char of barbequed meat. Despite cannabis smoke containing benzopyrene, the largest study of cannabis' effects on cancer found "no association between marijuana smoking and cancer [but] a 20-fold increase in lung cancer among people who smoked two or more packs of cigarettes a day." Once again, the evidence shows that tobacco is far more harmful than cannabis. Dr. Tashkin did a follow up study last year and his cannabis research findings remain consistent that cannabis use does not cause cancer.
The final point made by the study is that smoking cannabis while pregnant can potentially reduce the weight of a baby. While this is true, it also is not unique to cannabis. Caffeine has been shown to reduce birth-weight; alcohol has numerous harmful effects including fetal alcohol syndrome, and various pharmaceutical drugs have serious effects as well. Pregnant mothers should be aware of and assess the risks and possible benefits of medical cannabis.
Most media outlets have been reporting on this study as though it were something groundbreaking and new. The only major outlet to debunk the study is the Washington Post, which still leaves many half-truths unchallenged. This study is a re-hashing of Reefer Madness scare tactics and a poorly conducted literature review of the works of other, more competent, researchers. While the headlines seem alarming, the actual findings are boring and bring little to the discussion amid the flood of better-quality research coming out in support of cannabis. The tide is turning and people are becoming better educated about cannabis research every day; soon the drug war will be nothing but a memory.