If you ask 50 different people how long the effects of cannabis last, you will likely get 50 different answers. This can be a problem in figuring out how long a patient using the drug for medical purposes will be disabled.
A new meta-analysis of 80 papers has shortened this time frame. Depending on factors such as how the cannabis is consumed and how strong it is, the user can be disabled for between three and ten hours.
This information can help educate patients, help recreational users make better decisions about performing tasks such as driving after consuming cannabis, and help update laws to better reflect the reality of cannabis disorders. to give.
“THC can be detected in the body weeks after cannabis use, while it is clear that the duration of the disorder is much shorter,” explains psychopharmacologist Iain McGregor of the University of Sydney (USYD) in Australia.
“ Our legal frameworks should probably catch up and, as with alcohol, focus on the interval at which users are more at risk for themselves and others. Prosecution based solely on the presence of THC in blood or saliva is manifestly unjust. “
A meta-analysis is what it sounds like: an overview and analysis of the relevant scientific literature, cross-referencing the results to arrive at a finding based on a wider range of methodologies and topics (in this case people) than can be covered in a single study.
For this study, a team led by USYD nutritionist Danielle McCartney referred to 80 separate studies of disorders caused by tetrahydrocannabinol (THC), the intoxicant in cannabis, and performed the first meta-analysis of its kind.
Of those 80 papers, the team studied 1,534 “performance outcomes” of people who had used cannabis; that is, how these people performed in driving or similar cognitive tasks at different stages after using cannabis.
How long the disorder lasted depended on three main factors: how strong the dose of THC is; whether the cannabis was inhaled or taken orally in the form of food, capsules or drops; and whether the person was an occasional or frequent user of cannabis.
“Our analysis indicates that the disorder can last up to 10 hours if high doses of THC are consumed orally. However, a more typical duration of the disorder is four hours when lower doses of THC are consumed via smoking or vaporization and simpler tasks are performed.” McCartney said.
“This disturbance can last up to six or seven hours if higher doses of THC are inhaled and complex tasks, such as driving, are assessed.”
Interestingly, regular cannabis users can develop tolerance and perform better in cognitive tasks than casual users after consuming the same amount. It is therefore not easy to predict how much cannabis will harm a regular user, or for how long, as they may take higher doses to achieve the same level of intoxication as an occasional user.
“We found that incidental cannabis use disorders are much more predictable than regular cannabis users. Heavy users show significant tolerance to the effects of cannabis on driving and cognitive functioning, while typically showing some impairment,” said behavioral pharmacologist Thomas Arkell, also from USyd.
The findings suggest that most driving skills can return within five hours of inhaling cannabis, although this time may vary.
More research will need to be done on these time intervals for regular users to better characterize the effects of THC across the board. Once this is done, however, the information could guide the legislation, the researchers said.
“Laws should be about road safety, not arbitrary punishment. Given that cannabis is legal in an increasing number of jurisdictions, we need an evidence-based approach to drug driving laws,” said McGregor.
The research is published in Neuroscience & Biobehavioral Reviews