New research reveals how long it takes for cannabis to deteriorate

New research has shown for the first time how long cannabis users are likely to be affected and when they can be sure to drive.

The findings, say researchers and advocates, reinforce the case for changes in drug driving laws in much of Australia.

Researchers at the Lambert Initiative for Cannabinoid Therapy at the University of Sydney found that users were affected for three to ten hours after taking moderate to high doses of the intoxicating component of cannabis, tetrahydrocannabinol (THC).

THC can be detected in the body for weeks after cannabis use, meaning users can suffer fines and loss of license, even if they are not affected by the drug.

The research, published in Neuroscience & Behavioral Reviews, looked at 80 scientific studies on the effect of THC on driving performance over the past 20 years.

It was found that the exact level of deterioration depended on the dose, whether THC was taken orally or inhaled, and how often the person used the drug, among other factors.

“Our analysis indicates that the deterioration can last up to 10 hours if high doses of oral THC are consumed,” said the study’s lead researcher Danielle McCartney.

“However, a more typical duration of deterioration is four hours, when lower doses of THC are consumed by smoking or vaporizing and simpler tasks are performed.”

The study also found that regular cannabis users were less affected by THC than those who occasionally consumed cannabis.

Dr. McCartney said people could be affected for six to seven hours if higher doses of THC were inhaled and complex tasks, such as driving, were evaluated.

His research is the first comprehensive meta-analysis that puts a time frame on deterioration.

“Our tests should help people make informed decisions and policymakers make evidence-based policies and tell people how long they should wait before driving,” he said.

The Therapeutic Goods Administration (TGA) has approved 100,000 medical cannabis prescriptions in Australia.

Lambert Initiative academic director Iain McGregor said medical cannabis users were especially interested in knowing when it was safe for them to drive, even though the law was clear on the subject.

“You have a massive amount of prescription drugs to people who are told, ‘You can’t drive at all, you can’t even have a molecule of THC in the system,’ which is, you know, ridiculous.” Said Professor McGregor.

“THC can be detected in the body weeks after cannabis use, while it is clear that the deterioration lasts a much shorter period of time. Our legal frameworks will probably need to be updated.”

Former Magistrate David Heilpern said the investigation showed that laws on road drug testing needed to be changed.

Heilpern retired early, in part because of his frustration at seeing the license and sometimes livelihood of so many patients with medical cannabis be lost after being caught driving with small amounts of THC into the system.

“We had a situation where people were taking the medications as prescribed, not driving in any adverse way and yet they lost their license, were fined and got a criminal record,” he said.

“I started driving home from work, thinking, I just can’t do that.

Heilpern said cannabis was the only drug in Australia that could be obtained with a prescription but could not be driven even at a detectable level.

He is part of the Cannabis Law Reform Alliance, which advocates amending state laws, which provides medical cannabis users a defense if they test positive for a road drug test.

The defense already exists in Tasmania and there are bills before the Victorian parliament and South Australia. The NSW parliament rejected a bill on the issue in October.

“In NSW, we already have this law, because it applies to morphine,” Heilpern said.

“If you have a detectable level of morphine in your system and you can show that you have a prescription, you have a defense.

“All we have to do is do it for cannabis. It’s a very simple amendment and it solves the problem.”

Gino Vambaca, co-founder of Harm Reduction Australia, said Australian laws punished people for past drug use, not for unsafe driving.

“It’s no longer a road safety campaign, it’s a detection and penalty campaign,” he said.

“We don’t accept people who use drugs and drive, but what we are saying is that the police are not even trying to measure the deterioration.

“We need to tell people who use medicinal cannabis,‘ Do you want to drive or do you want to relieve the pain, because you can’t do both? “

“And that’s a horrible choice they have to make.”