Most People Using Prescribed Cannabis Drive Within Hours of Taking It, Study Finds

New Australian research has raised fresh concerns about road safety. The findings centre on prescribed cannabis and driving behaviour across two national samples. Most people who used THC-containing products reported getting behind the wheel within three hours of taking them.

NDARC at UNSW Sydney published the study in February 2026. Researchers drew on data from two surveillance programmes: the Illicit Drug Reporting System (IDRS) and the Ecstasy and Related Drugs Reporting System (EDRS). Together, these programmes surveyed 1,555 people who regularly use illicit drugs. Participants came from all Australian capital cities in 2025.

Prescribed Cannabis and Driving: What the Numbers Show

While prescribed cannabis use was not widespread in either group, the numbers among those who did use it tell a clear story.

In the EDRS sample, 15% of the 690 participants reported using prescribed cannabis or cannabinoid products in the past six months. Of those, 96% confirmed their product contained THC. Furthermore, among recent drivers in this group, 84% reported driving within three hours of taking prescribed cannabis.

The IDRS sample told a similar story. Seven per cent of the 865 participants had used prescribed cannabis in the past six months. Moreover, 97% of those products contained THC. Among recent drivers in this group, 76% reported driving within three hours of use.

Fewer than five participants across both samples reported being detected by roadside drug testing after such driving. That figure is too small to report statistically. Nevertheless, these people remain at real risk of positive tests and criminal charges.

A Legal Grey Area Around Medicinal Cannabis Driving Laws

The issue goes well beyond personal choice. In almost every Australian state and territory, any detectable amount of THC in a driver’s blood or oral fluids is illegal. This applies even when the driver holds a valid prescription. It also applies even when they feel no impairment at all.

Tasmania stands as the only exception. There, a limited legal defence exists for prescription holders who can show they were not impaired at the time.

This situation puts medicinal cannabis patients in a very different legal position from people taking other impairing medications. Doctors prescribe morphine and methadone to patients who drive regularly. Authorities assess those drivers on actual impairment, not merely on whether the substance is present. By contrast, prescribed cannabis and driving do not enjoy the same framework. The NDARC authors suggest this gap traces back to the historical classification of cannabis as a prohibited drug. That classification has not caught up with its legal therapeutic status, which Australia recognised in 2016.

Broader Research Confirms the Pattern Is Not Isolated

The NDARC findings align with results from wider patient surveys. A separate study of 806 Australian medicinal cannabis patients found that 35% of drivers reported typically driving within three hours of consuming cannabis in the previous month. That research appeared in the journal Transportation Research Part F in 2026. Consequently, this behaviour is not confined to people who also use illicit drugs. It appears across the broader population of medicinal cannabis users.

Taken together, the evidence points to a systemic issue. People who hold a legal prescription are routinely placing themselves at legal risk. In many cases, this happens not because they are acting carelessly, but because the medicinal cannabis driving laws simply have not kept pace with clinical reality.

In addition, the scale of medicinal cannabis prescribing in Australia has grown substantially since legalisation. As of recent years, Australia has become one of the largest medicinal cannabis markets in the world. That growth makes the policy gap harder to ignore.

Calls for Regulatory Reform

Study authors Julia Uporova, Amy Peacock and Rachel Sutherland add their voices to calls for reform. Specifically, they argue that Australia needs to review how road safety rules interact with prescribed cannabis and driving. Currently, the system treats medicinal cannabis patients differently from those on other psychoactive medicines. That difference is difficult to justify on evidence alone.

The question of how long THC impairs driving is genuinely complex. Impairment does not map neatly onto detection windows. Oral fluid tests can return positive results long after any psychoactive effects have worn off. Critics of the current framework have made this point for years. As a result, patients face legal jeopardy even when they are, by any reasonable measure, safe to drive.

For people using prescribed cannabis to manage chronic pain, epilepsy or anxiety, this creates a real dilemma. They are legally entitled to take their medication. Yet they risk criminal sanction for driving, even when they feel fully capable of doing so safely.

What This Means for Medicinal Cannabis Driving Laws

Road safety is a serious concern. The risks that come with driving while impaired by THC are real and well-documented. However, a system that makes no distinction between impairment and mere detection raises its own serious questions. Fairness, proportionality and public health all deserve consideration.

Medicinal cannabis use is growing steadily across Australia. Therefore, the tension between current driving laws and clinical prescribing practice will only intensify. The NDARC data makes a strong case that policy must evolve alongside the evidence. Without reform of medicinal cannabis driving laws, the current rules risk punishing patients rather than protecting roads.

Source: unsw.edu