A scientific dilemma
The SGRM study presents the different approaches to assessing driving ability during Recreational Consumption under the influence of THC:
- Impact-oriented approach: Here, driving ability is assessed on a case-by-case basis – a very complex procedure.
- Per se approach: A fixed threshold is defined above which driving ability is considered impaired.
- Zero-tolerance approach: Any detection of THC in the blood leads to the assumption of unfitness to drive.
Currently, Switzerland operates a modified zero-tolerance approach with a limit of 1.5 µg/L THC in the blood . However, this limit does not take into account individual tolerance or the effects of THC in long-term users, particularly patients who take cannabis for medical reasons.
The study concludes that a limit based on effect for THC – as with alcohol – is not scientifically feasible. Instead, a per se approach with a slightly raised limit of 1.7 µg/L in whole blood proposed to rule out any relevant impairment of driving ability.
Fitness to drive and driving ability with medical cannabis
Individuals who take cannabis for medical reasons as prescribed by a doctor are not automatically fit to drive. Participation in motorized road traffic should only occur after a positive assessment by a traffic medicine specialist. This assessment takes into account the underlying medical conditions, their medication treatment, the indication for cannabis therapy, individual tolerance, and consumption patterns regarding psychotropic substances such as alcohol, cannabis, or other drugs.
Under current Swiss law, there is a general "zero tolerance" policy for THC. An exception exists, however, if THC-containing medications have been prescribed by a doctor. In these cases, driving ability must be assessed individually. Physicians are obligated to inform patients about their driving ability while taking THC medication as part of the mandatory safety consultation. Ultimately, the responsibility for participating in road traffic only when fit to drive rests with the individuals themselves.
If a traffic incident does occur, the assessment of driving ability is carried out as part of a so-called three-pillar report. This includes police observations, medical examination findings, and forensic toxicological analysis results. Driving-related effects of the underlying medical condition or other prescribed medications are also factored into the assessment.
However, a crucial problem remains the lack of legal certainty. Without clear, confirmed fitness to drive, there is a significant risk of losing insurance coverage in the event of an accident. Benefits can be denied if it is proven that driving ability was impaired by THC medication. This legal and financial risk underscores the importance of transparent and reliable regulations in road traffic.
The MEDCAN Association is committed to addressing these injustices. Differentiated approaches are needed that take into account the individual circumstances of those affected and give them a fair chance to preserve their mobility and their rights.
Here you can find the full report by the Swiss Society of Legal Medicine (SGRM), commissioned by the Federal Roads Office (ASTRA).
From the perspective of those affected, this is unfair treatment
The scientific findings are an important contribution, but what does that mean in practice? Our experience as Association MEDCAN shows that many chronically ill people are severely restricted by the current regulations – restrictions that not only make everyday life more difficult, but can also have existential consequences.
A male and a female patient have shared their stories with us – two examples that represent the numerous challenges many affected individuals face. Their experiences demonstrate how urgently changes in practice are needed to guarantee access to safe and fair treatment.
"Either cannabis or a car."
A man from the mountains, who consumes a minimal amount of 0.5 grams of cannabis flowers with a THC content of 25% daily and is thus well-controlled, experienced a true nightmare. He relies on his car – not only for commuting to work, but also to maintain social contacts and manage daily life. The nearest public transport connection is six kilometers away and virtually inaccessible in winter.
Following a house search – triggered by the possession of cannabis flowers – the case was reported to the road traffic authority. He had to undergo a level 4 assessment, during which the doctor told him: "Either cannabis as medicine or a car."
To keep his driver's license, he immediately stopped taking the medication. Since then, he has again been suffering from chronic sleep problems and nightmares, and a significantly reduced quality of life. Furthermore, he must submit regular urine samples for at least a year to prove his abstinence – a measure that is associated with high costs.
"To remain mobile, I had to go through an odyssey."
The second story we received also illustrates the profound impact of the current regulations. Andrea, 55 years old, is immunocompromised and lives with chronic fatigue and joint pain. She relies on her car to manage daily life, as stressful situations like rushing to change public transport are unthinkable for her.
Following a routine check by the disability insurance office, the road traffic authority gained access to her complete file – including details unrelated to her fitness to drive. Her driver's license was revoked due to her THC medication.
The consequences were devastating: Andrea had to discontinue the therapy and switch to other medications that had severe side effects. Only after months of abstinence and further assessments was she allowed to drive again, and even then, only under strict conditions. Ironically, tests showed that her reaction time was better with THC in her blood than without .
Here you can read Andrea's whole story.
The position of the Association MEDCAN
The current regulations lead to massive injustices in practice. We demand a differentiated regulation that distinguishes between actual impairment and a purely positive THC test. It cannot be that those affected, with stable medication and demonstrable fitness to drive, are excluded from road traffic.
For many chronically ill people, especially in rural areas, a car is essential for managing daily life. Losing their driver's license can have existential consequences and promote social isolation.
Traveling responsibly
As an Association , we would like to emphasize that cannabis patients do not intend to drive while impaired. On the contrary, they are very concerned about driving responsibly.
However, it's important to understand that the effects of cannabis are very different from those of alcohol. While alcohol is eliminated linearly from the body, THC – the psychoactive ingredient in cannabis – remains detectable in the blood for significantly longer. This means that you can test positive for THC days or even weeks after ingestion, even though you are no longer experiencing any impairment.
Current legal limits for THC in road traffic are designed for Recreational Consumption and do not take into account the situation of patients who take a stable dose and do not experience intoxication. These limits result in many people losing their mobility, even though they use their medication responsibly and are capable of driving safely.
As an Association , we are committed to ensuring that these differences are better understood and taken into account in legislation. Our goal is to ensure that those affected are not treated unfairly and do not lose their mobility simply because they are taking necessary medication. Responsibility and road safety remain our top priorities.
An appeal to politicians
The MEDCAN Association is advocating for adjustments to the regulations. Our demands:
- Introduction of a realistic control system that does not discriminate against medical users.
- Individual assessments that are scientifically sound and conducted fairly.
- Protecting the data of those affected in order to prevent arbitrary decisions.
We urge everyone to advocate for a fairer transport policy. Together, we can help ensure that chronically ill people can remain mobile and lead independent lives despite their medication. Become a member or support us with a donation .
