Around 25,000 currently use medicinal cannabis products. They may be prescribed to relieve symptoms and pain associated with certain , for chemotherapy-induced nausea, or during palliative care.
In Australia, it’s an offence for someone to drive if they’re using medicinal cannabis products containing tetrahydrocannabinol (THC, the main psychoactive component of cannabis). If they injure another person in a traffic accident, they may face criminal charges of driving while impaired.
If they’re picked up at a roadside test, in the same way as someone who tests positive to illegal drugs.
But , this could soon change. A proposing to treat medicinal cannabis users like people who use other prescription drugs, rather than illegal drug users, is gaining support.
Generally, being on medication doesn’t mean you’re not allowed to drive. It seems fair that medicinal cannabis users should be treated in the same way as people who use legal drugs.
But we also need to weigh up any potential risks. Driving a car is a complex task that requires a driver to be attentive, competent and capable.
The relationship between cannabis and driving impairment is complex
The degree to which cannabis might impair a person’s ability to drive safely often depends on , to drive after using it, the , and the .
Compared with drug-free drivers, drivers with have modestly increased odds of being responsible for a traffic accident resulting in injury or death.
High-THC cannabis also reduces a driver’s ability or respond to .
It also affects a driver’s attention, and , the greater the impairment.
Conversely, some research has suggested THC has on the likelihood of being involved in a crash.
Medicinal cannabis is different to the illegal stuff
Medicinal cannabis typically contains much less of the intoxicating component (THC), and more of the components that don’t produce a “high” (cannabidiol, or CBD). Compared with THC, CBD has on mood, awareness, thoughts, feelings and behaviour.
Most often, are CBD-only.
It’s not clear how CBD-only treatments might affect driving, although . As it stands, patients taking CBD-only medicines , as long as they are not impaired.
Australian medicinal cannabis products are generally CBD-only | Shutterstock
Sometimes, medicinal cannabis products are CBD/THC-balanced or THC-dominant. How medicinal cannabis might impair a person’s ability to drive safely seems to depend . CBD does not offset this intoxicating effect.
Roadside testing
In Australia, THC is a under the Poisons Standard. Victoria has a zero-tolerance drug-driving policy for controlled drugs. This currently includes that contain THC.
Under this system, for cannabis (THC), (meth)amphetamine or 3,4-Methylenedioxymethamphetamine (MDMA) using a saliva test. Drivers who return a positive result will undergo verification (additional testing of a sample sent to a laboratory) to confirm how much of a drug is present.
The for testing positive to THC is a six-month loss of licence and a fine. Drivers must also complete an education program.
The process is similar in other states.
Roadside tests can’t differentiate between illegal recreational and medicinal cannabis products, or determine the THC concentration.
So patients legally prescribed medications that contain THC can be prosecuted in the same way as a driver who has consumed a higher level of THC for a non-medical reason.
High-THC cannabis reduces a driver’s ability to control the car or respond to unexpected situations | Shutterstock
Internationally, there’s been a move away from zero-tolerance approaches to systems that use thresholds to determine whether a person driving under the influence of THC is likely to be impaired.
, and now , have introduced limits of between 1, but no more than 5 nanograms of THC per millilitre of blood. This roughly equates to a blood alcohol content of 0.05%.
Penalties for having higher levels of THC that factors in the level of drugs in the driver’s system, and whether the incident is a first or repeated offence. These laws apply to all drivers, including those with a medical authorisation to use cannabis.
The road ahead
As many as Australian patients who use medicinal cannabis drive within three hours of taking their treatment. Some medications containing THC can be detected by roadside drug tests more than , so patients who drive within this window may well be charged.
Determining whether patients who use medicinal cannabis products pose a risk to themselves or other road users is important for deciding what (if any) legislative changes would be appropriate. We need more research before we can move to a system like Canada or the US.
Introducing a conditional licence, subject to periodic review, may be one way of supporting people who use medicinal cannabis to drive lawfully and safely. A central registry could help law enforcement and health-care providers quickly reference what medication a driver is taking, at what dose, and for how long they’ve been using it.
As with other potentially impairing (but legal) medications, using might be an easy way to help patients make better decisions about whether they are feeling well enough to drive when using these medications.
With greater access to a wider range of medicinal cannabis products, it’s important we support the rights of patients who use these medications and continue to drive, as well as ensuring the safety of all road users.
Future decisions must include equal input from patient advocates, research groups, road safety groups and law enforcement.
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