A recent review of twenty studies conducted by researchers at the University of Sydney is challenging the notion that there is a ‘hangover effect’ for marijuana use the day after consumption. Results of this research, published in the journal Cannabis and Cannabinoid Research, suggest that the majority of performance assessments did not detect a negative impact on cognitive function and safety-sensitive tasks. This has implications for current policies that punish drivers and people in safety-sensitive positions for cannabis consumption that occurred weeks prior to drug tests.
The review included 350 performance assessments, with only 3.5% showing a potential ‘hangover’ effect. However, these studies were conducted without randomized, double-blind, placebo-controlled methods and all were over 18 years old. Additionally, the magnitude of the observed effects was not well reported.
These findings are particularly noteworthy when considering evolving policies regarding driving and employment for cannabis consumers. The study found little evidence to support recommendations that individuals should abstain from such activities for at least a day after recreational marijuana use. This could have serious ramifications for those who are required to refrain from medicinal cannabis used to treat conditions such as insomnia or chronic pain out of fear of a positive workplace or roadside drug test.
Drug tests are unable to detect active THC metabolites related to intoxication, which can remain in the system for weeks or months after usage. This has led to labor shortages in certain sectors such as trucking, where tens of thousands of commercial truckers are testing positive for marijuana due to federally mandated screenings. The U.S Department of Transportation is set to complete a report on research barriers that inhibit the development of a standardized test for marijuana impairment on roads by November 2023.
Evidence surrounding the relationship between THC concentrations in blood and impairment is inconclusive; however, a 2019 study concluded there was no statistical increase in the likelihood of an accident when driving at legal THC limits. Separately, the Congressional Research Service reported conflicting results on the impact of marijuana consumption on a driver’s risk of being involved in a crash, while another study found smoking CBD-rich marijuana had “no significant impact” on driving ability despite exceeding the per se limit for THC in blood plasma.
The findings of this study have important implications for current regulations surrounding both driving and employment. Many jurisdictions have laws that impose restrictions on driving or working while under the influence of marijuana. However, if marijuana does not result in any residual impairment effects, then such regulations may be overly restrictive and may even be unjustified.
The results also underscore the need for further research into this area. While this study provides valuable evidence regarding long-term impairment associated with marijuana use, it is only one piece in a much larger puzzle. More research is needed to determine whether there are other factors involved in determining how long an individual might remain impaired after using marijuana. For example, it is possible that different types or doses of marijuana could result in different levels or types of impairment.
In addition to further research into the potential long-term effects of marijuana use, this study also raises important questions related to public policy and regulation. For example, it suggests that existing regulations surrounding driving and employment may be overly restrictive with respect to marijuana use. As such, it would be beneficial for policy makers to consider revisiting these rules and regulations in light of this new evidence in order to ensure that they are effective but still protect public safety.
Ultimately, the findings from this study highlight an important issue with respect to public health policy related to marijuana use: current regulations may be unnecessarily restrictive and even unjustified when considering available scientific evidence about long-term impairment effects from marijuana use. This study provides valuable insights into this issue and highlights the need for further research into this topic as well as revised policies that appropriately reflect our current understanding about marijuana’s potential risks and benefits.