Comparative harms assessments for cannabis, alcohol, and tobacco: Risk for psychosis, cognitive impairment, and traffic accident

Abstract

Researchers have associated cannabis use with risk for psychosis, cognitive impairment, and traffic accident. However, this review shows that the association between moderate cannabis use and psychosis is no stronger, and often considerably weaker, than the corresponding association for moderate tobacco use. The same holds for associations with cognitive impairment. For the risk of traffic accident, the review confirms that the risk from alcohol use is substantially stronger than the risk from cannabis use, while the corresponding risk from tobacco use appears to be almost as strong as that from cannabis use. It thus appears that the risk for psychosis, cognitive impairment, and traffic accident associated with cannabis use is generally comparable to that from tobacco use. The article discusses different interpretations of these comparative harms assessments and presents two points of methodological critique to argue that the risks associated with cannabis and other generally criminalized drugs are probably exaggerated. First, any measurement of harms associated with high escapist activities such as drug abuse will be affected by the general dysfunction associated with the underlying reason why a person settles for frequent escapism. From this perspective, cannabis and tobacco use disorder are probably both associated with underlying problems and life issues that are, in and of themselves, associated with psychopathology, and researchers should be careful not to conflate the selection effect from belonging to the population segment that opts for high escapist lifestyles with any (putative) harmful effect from drug use itself. Second, criminalization probably shifts the composition of the user population in the direction of more dysfunctional users. From this perspective, the association between substance use disorder and underlying problems and life issues is stronger for criminalized substances, since people who live troubled lives are less likely to be deterred by the prospect of legal problems.

Racial and religious motives for drug criminalization

“…Today, the xenophobia that formed the basis for the gross exaggerations of the early twentieth century appears to live on in more muted forms of exaggerations in contemporary drug harms research. As pointed out for instance in Johnstad (2022a), there seems to be a systematic inconsistency in how we speak about the dangers from licit and illicit drugs. Why is the moderate association between cannabis use and psychosis, with a median odds ratio of 1.75 in the overview of meta-analyses presented in Johnstad (2022a), regarded as a major societal problem, while much less attention is given to the apparently stronger association between tobacco use and psychosis, with a median odds ratio of 2.70?…”

“…As pointed out for instance in Johnstad (2022a), there seems to be a systematic inconsistency in how we speak about the dangers from licit and illicit drugs. Why is the moderate association between cannabis use and psychosis, with a median odds ratio of 1.75 in the overview of meta-analyses presented in Johnstad (2022a), regarded as a major societal problem, while much less attention is given to the apparently stronger association between tobacco use and psychosis, with a median odds ratio of 2.70? We find the same tendency for a range of other drug-related issues, from violence to traffic accidents to brain damage: while the main culprit for such harms is actually alcohol, a lot of our attention is instead diverted toward less problematic illicit drugs.…”

“…For the issue of acute lethal toxicity, Gable (2004; see also Lachenmeier & Rehm, 2015) found that alcohol had a safety ratio of 10, comparing unfavorably to the safety ratios for instance of cocaine (15), MDMA (16), LSD (1000), and cannabis (>1000), and there is broad agreement in the research literature that although some forms of illicit drug use may be associated with violence, the association is much stronger for alcohol use (Boles & Miotto, 2003; Coomber et al, 2019; Hoaken & Stewart, 2003; White et al, 2019). Furthermore, while much has been said about the association between cannabis use and psychosis, a recent review by Johnstad (2022a) found that the association for moderate cannabis use is not stronger than those between psychosis and moderate tobacco use. Similarly, Schoeler et al (2022) found that in a sample of 230,000 respondents, the rate of psychotic symptoms associated with cannabis use was at about the same level as alcohol-associated psychosis.…”

Cannabis, research ethics, and a duty of care

“…The value of distinguishing research conducted where people who use cannabis are forced to engage in criminal interactions versus those who can simply visit a store is important. This observation is not new (Goldstein, 1985) but has been insufficiently framed as a distinct methodological limitation (Johnstad, 2022) with undertheorized ethical implications. One option is to reduce future harm by explicitly confronting the damage done by the criminal justice system and its supporting institutions in the past and present (Quinney, 1970).…”

“…More than a century of evidence suggesting cannabis is relatively innocuous compared to legal drugs like alcohol and tobacco (Wheeldon and Heidt, 2022b). Cannabis does not appear to be a driver for mental health conditions, including psychosis (D’Souza et al, 2022; Johnstad, 2022).…”