Discussion And Conclusion
The use of illegal drugs is limited to a small part of the population. Not many people consume amphetamines, ecstasy, cocaine, or heroin. The most popular illegal drug by far is cannabis. However, even for the most popular illegal drug, heavy use is quite rare. And whereas a substantial proportion of the population has used cannabis in their lifetime, for many their use was a short-lived experiment. Even among individuals who persist in cannabis use, many do so on a recreational basis. Despite a large number of epidemiological studies and a handful of econometric studies little is known with any degree of certainty about the health effects of illegal drug use. Researchers agree that drug use is associated with worse health. The issue is whether this association is causal, with drug use causing poor health, or whether spurious correlation or reverse causality underlies this association. The main impediment to determining the nature of the relationship between illegal drug use and health is that the optimal setup for addressing this issue is a randomized control trial in which individuals are randomly allocated to the treatment group (who are administered illegal drugs) or to the control group (who receive a placebo). However, this type of experiment is not possible for at least two reasons. First and foremost, individuals will always know whether they are in the treatment group receiving illegal drugs, or in the control group receiving the placebo. Second, long-term exposure to illegal drugs would be necessary in order to determine the health effects, and this would be rather unethical should the outcome be that there are serious health problems related to illegal drug use. The so-called ‘natural experiments,’ in which a policy change that affects drugs use is exploited as if it were an experiment, are rare simply because drug policies have the tendency not to change.
The lack of econometric research that seeks to identify causal effects of drug use on health is surprising but likely to be related to lack of good data as a basis for the research. Drug use is not a static phenomenon. On the contrary, dynamics in use are very important. Within the population some individuals may start using a drug but others will abstain. Among those who have started using a drug there are individuals who will stop using and other individuals who will persist in drug use. By and large, in the population there are never-users, experimental users, and persistent users. Even within the group of persistent users there may be transitions from high intensity of use to low intensity of use and vice versa. To understand the dynamics of illegal drug use, information is needed from the time when individuals are first confronted with the choice of whether to use a particular drug. Ideally, this information should capture how relevant circumstances change over time. Information that could be relevant includes: family situation, experiences at school, changing drug supply conditions, and drug prices. Unfortunately, this type of information is not typically available. Another issue which makes it hard to research in this area is the fact that it is hard to quantify drug use. Whereas standard quantity measures are available for tobacco (cigarettes per day) and for alcohol (standard units of alcohol per day), there are no obvious standard quantity measures for the use of illegal drugs.
Despite the absence of experimental research it is still possible to draw some conclusions from previous research on the direct and indirect health effects of illegal drug use. Intensive use of illegal drugs over a long period of time generates negative health effects for its users whereby the magnitude depends on the nature of the drug involved. Whether short-term use or long-term, recreational use is harmful is not clear. For cannabis, the evidence finds that use is neither necessary nor sufficient for mental health problems to occur. It could be that individuals who are susceptible to mental health problems are vulnerable for cannabis use, but as yet this is unclear. Most likely, experimenters will not suffer serious health effects, whereas the same holds for persistent but recreational users. The group of persistent heavy users is at risk of negative health effects. However, the size of this group is limited to 1% or 2% of the adult population. In this sense, from an aggregate point of view, the magnitude of the health effects of illegal drug use is limited. Nevertheless, for individuals the negative health effects may be severe. How severe it may be is yet to be established.
Given the limited circumstances for which cannabis use may pose a threat of harm, there is growing interest in possible medical applications of cannabis, the so-called ‘medical marijuana’ most notably as a treatment for the symptoms of muscle spasm and tremors in multiple sclerosis patients and the symptoms of vomiting and nausea in cancer patients undergoing chemotherapy (Hall et al., 2001). Cannabinoids may allay pain, improve sleep, and possibly inhibit degenerative processes (McCarberg, 2007). Caulkins et al. (2012) refer to a summary of 12 double-blind clinical trials where 57% report positive outcome of cannabis use, 33% found no effect and 10% found adverse outcomes. Research on the therapeutic use of cannabis and cannabinoid drugs is hampered by ‘Catch 22’ situation that as long as cannabis is illegal the medical benefits cannot be established in a way that it would be accepted as a treatment and cannabis remains illegal if the medical benefits of cannabis use cannot be established. Nevertheless, 18 US states and the District of Columbia allow patients who have a recommendation from a doctor to use cannabis for medical purposes without the risk of being prosecuted.
When assessing the health effects of illegal drug use some caveats are important to keep in mind. First, all health effects are established under one type of policy regime, prohibition. Although there is variation in the way prohibition is implemented, there is no country or jurisdiction that has legalized selling, buying, or using any illegal drug. In the USA, Colorado and Washington states have recently passed referendums to legalize cannabis but at the time of writing, the framework for implementing legalization was yet to be established. However, the legal status of a drug may affect the relationship between drug use and health. Furthermore, because it is an illegal activity, it is not easy to collect reliable data on drug use. A second caveat is that the health consequences of using an illegal drug are likely to depend on the manner in which it is consumed. Smoking heroin, for example, is less dangerous than injecting heroin and inhaling cannabis that has been vaporized is less dangerous than smoking cannabis. A third caveat to keep in mind is that the health risks posed by specific illegal drugs may have changed over time. For example, in recent years, the proportion of D9-tetrahydrocannabinol present in cannabis is thought to have risen, whereas the proportion of cannabidiol is thought to have decreased. ∆9-tetrahydrocannabinol is believed to exaggerate the psychotic effects of cannabis, whereas cannabidiol is thought to moderate the psychotic effects. However, due to paucity of information on the composition of cannabis, the health effects of any changes are unknown.
It is concluded that adverse health effects of cannabis use are clearly present but their magnitude seems rather limited. Nevertheless, using illicit drugs is not good for one’s health. Even cannabis, which is considered to be a soft drug in some countries because of its limited health effects, has a negative health effect. Whether one should worry about this is another matter. In the grand scheme of things cannabis use – and even hard drug use – has a limited health effect compared with other risky behavior. Heavy cannabis use and early onset of cannabis use, which often but not always coincide, have the largest negative health effects. Preventing youngsters from starting to use cannabis or least preventing them from doing this early on in life could be sufficient to prevent serious health effects.
As to the health effects of other illegal drugs the weight of evidence supports the finding that the harms associated with cannabis use are much less serious than those associated with ‘hard’ drugs such as cocaine or heroin and may even be smaller than those associated with alcohol and cigarettes. And although it is generally acknowledged that there are risks associated with long-term heavy use of cannabis such as respiratory diseases, cancer, and perhaps psychotic disorders, only a small fraction of those who ever use cannabis actually become long-term heavy users.
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