For many patients, medical cannabis is a key part of managing a chronic condition. As access to prescribed products grows, it’s vital to talk about how this treatment interacts with daily life, especially driving. Navigating road safety rules while on treatment is a serious concern for many patients.
A recent Australian study assessed responses from the latest Cannabis as Medicine Survey 2022-2023 (CAMS-22). It offers important insights into the attitudes and behaviours of medical cannabis users when it comes to Driving Under the Influence of Cannabis (DUIC), defined in the survey as ‘driving while high’.
This research highlights the complex balance policymakers and patients must strike between equitable access to treatment and maintaining road safety.
Understanding Driving Under the Influence of Cannabis (DUIC)
The CAMS-22 study surveyed Australian adults who had used cannabis for medical purposes in the past year and who had also driven a vehicle in the past 12 months.
Key Findings on DUIC:
- Prevalence: Over one-quarter of respondents (28.3%) reported driving under the influence of cannabis (DUIC) in the past year. This figure is similar to previous CAMS studies.
- Main Reason for DUIC: The most common reason (69.1%) for DUIC was that patients felt they were unimpaired.
- Many patients who reported DUIC believed they could accurately assess their driving ability (80.0%), tend to drive more carefully (84.1%), and leave a larger gap between vehicles (58.5%) after using medical cannabis. This suggests a belief in their ability to use compensatory strategies.
- Wait Times: When asked about how long they typically wait before driving, a significant portion (31.5%) waited 7–12 hours, and 17.5% waited 13–24 hours.
What Factors Increase the Risk of DUIC?
The study identified several factors associated with a significantly increased likelihood (higher odds) of driving while high.
Factors Associated with Higher DUIC Risk:
- Frequency of Use: Using medical cannabis six or more times per day was strongly associated with much higher odds of DUIC compared to using it once a day.
- Route of Administration: Inhaled methods were linked to a greater risk compared to oral ingestion.
- Smoking was associated with the highest odds (2.53 times higher than ingestion).
- Vaporisation was also linked to higher odds (1.40 times higher than ingestion).
- Gender: Male respondents had higher odds of reporting DUIC compared to females and non-binary/other individuals.
- Perception & Beliefs: Individuals who did not believe that medical or non-medical cannabis impairs driving were significantly more likely to engage in DUIC.
The Impact of Roadside Drug Testing
Roadside drug testing emerged as a powerful deterrent, but also as a significant barrier for patients accessing prescribed treatment.
- Deterrent Effect: Nearly 69% of all respondents said that the presence of roadside drug testing deterred them from driving after using medical cannabis.
- Treatment Barrier: However, over half of respondents (51.3%) also stated that roadside drug testing influenced their treatment decisions or deterred them from using medical cannabis entirely.
This highlights a key tension. Enforcement strategies designed to promote road safety, like roadside drug testing, can unintentionally create a barrier to medical care for legitimate patients.
Importance of Further Research and Patient Communication
For patients using medical cannabis, road safety is a critical issue. The CAMS-22 study affirms that a patient’s perception of risk and the legal landscape are pivotal in influencing driving behaviour.
While some small, early simulator studies suggest that prescribed medical cannabis, when used as directed to manage a health condition, might not significantly impair driving ability , larger, controlled trials are still needed to fully understand the impact.
Road Safety and UK Medical Cannabis
While the CAMS-22 study focuses on Australia, the core tension between using prescribed medicine and maintaining road safety is directly relevant to UK patients.
- National Guidance and Legal Requirements: It is important to follow any national guidance regarding driving whilst prescribed medical cannabis. In the UK patients do not need to inform the DVLA of their prescription, but they should never drive if they feel or are impaired. This is in direct contrast to the actions of patients in the CAMS-22 study.
- General Guidance: All patients should be advised to avoid driving or operating heavy machinery until they have a stable dose and fully understand how their medicine affects them. Patients should never drive, operate heavy machinery, or sign legal documents if they are or feel impaired by their medication.
- Impairment Risk: Medical cannabis products can cause concentration impairment and drowsiness as a side effect. They may therefore reduce reaction times and coordination. This risk may be increased when co-administered with other sedatives, such as alcohol or benzodiazepines.
- High-Risk Periods: The risk of impairment is particularly high under specific circumstances:
- Starting medical cannabis or a new formulation.
- Immediately after a change in dose, especially an increase.
- If the patient is on a high dose or appears sensitive to side effects of tetrahydrocannabinol (THC)
- If the patient is experiencing side effects like blurred vision, drowsiness, or poor attention.
The behaviours observed in the Australian study, where many patients who reported DUIC believed they could drive safely by using compensatory strategies, stand in direct contrast to this safety-first principle. Patients should instead avoid driving until zero impairment is confirmed, regardless of perceived safety, particularly during periods of dose change or when side effects are present.
