Driving and occupational safety assessment in the context of substance use

Background

Impaired driving is the largest contributing factor to serious motor vehicle collisions in Canada.¹ In 2015 approximately 30% of all motor vehicle fatalities in Canada were due to alcohol-related crashes, and 30.9% of fatally injured drivers had positive test results for alcohol.² After alcohol, cannabis is the most common substance implicated in impaired driving in Canada³; data from the National Cannabis Survey (administered after cannabis became legal) indicated 14.7% of respondents had driven within 2 hours of consuming cannabis.⁴ Before the legalization of cannabis, cocaine was the second most commonly detected unregulated substance after cannabis,⁵ and 27.2% of fatally injured drivers had positive test results for central nervous system stimulants such as cocaine and methamphetamine.² While opioids are a less prevalent contributing substance to impaired driving, 3.1% of drivers surveyed in Ontario between 2011 and 2016 reported having driven under the influence of prescription opioids.⁶

Regarding substance use and occupational safety, there are limited studies on the prevalence and impact of substance use in the workplace.⁷ The National Cannabis Survey found that 13.4% of individuals who reported cannabis use said they consumed cannabis before or at work, with this behaviour more likely among those reporting daily or almost daily use versus individuals with less frequent use.⁸ However, a low prevalence of substance use at work has been reported, with data from a US workforce survey published in 2006 showing only 3.1% of workers who used substances did so in the workplace.⁹

Evidence from literature and best practices for assessments

Studies suggest that acute intoxication from substance use affects executive functioning. Both alcohol and cannabis intoxication slow down reaction time and motor coordination, although next-day driving is not affected.¹⁰ Opioids may induce sedation, slow reaction times, impair coordination, and blur vision, while stimulants may increase alertness, energy, and attention but also impair executive decision making, impulse control, movement perception, and working memory, as well as lead to increased risk taking. During the withdrawal phase, stimulants may also cause inattention, fatigue, and sleepiness.¹¹ Outside of instances of acute impairment, it is also important to understand the potential for impaired functioning when an individual is not acutely intoxicated, as this can influence how assessments for occupational and driving safety are made. More evidence is needed to better understand substance use and post-intoxication impairment.

The Canadian Centre on Substance Use and Addiction and the Canadian Medical Association have published resources and guidelines around determining medical fitness to drive and return to work,^11,12 highlighting that every physician who examines a patient for this purpose must always consider both the interests of the patient and the safety of the public who will be exposed to the patient’s driving or occupational work. During the examination, the physician should look for physical disabilities and assess the patient’s mental and emotional fitness to drive or work safely. A single major impairment or multiple minor functional defects may make it unsafe for the person to work or drive. Likewise, physicians should be aware of the circumstances in which patients are likely to function or work, paying special attention to safety-sensitive situations,¹² as well as physicians’ responsibility or legislated requirement to report patients to regulatory bodies.

How does a learner develop assessment skills?

Skills are often consolidated with the use of tools, flow charts, or algorithms, with driving and occupational safety being no exception. The first step in the evaluation of safety involves both a self-assessment by the provider and a fulsome assessment of the patient. In self-assessment there are many factors to consider (Box 1),¹³ such as one’s relationship with the patient and one’s ability to gather information, as well as the impact of an assessment on the therapeutic relationship. In many instances, it may be more appropriate to refer a patient for an independent medical assessment (ensuring no conflicts of interest exist and no non–evidence-based practices would be employed) and act only as a family physician in supporting the patient’s return to work and mental health optimization.

The next step in the evaluation of safety in the context of substance use is the assessment, which starts with a fulsome medical history that includes any history of substance use, after which a detailed functional inquiry, screening test panel, and careful physical examination may be conducted (Table 1).¹³ Overall, the physician’s role in the assessment is to report objective findings to a regulatory body to aid in the regulatory body’s decision regarding licensing or return to work, although some physicians may also choose to share diagnoses or assessments based on their training or expertise.

An algorithmic approach (Figure 1)¹³ to assessments may be helpful, particularly for learners as they decide the best approach when a patient is using substances. In addition, a sample letter to regulatory bodies is provided in Figure 2 to illustrate how to report information while refraining from offering opinions outside of one’s medical provider expertise.¹³

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Figure 1.

Algorithmic approach to assessment of substance use and driving or occupational safety

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Figure 2.

Sample letter to licensing authority