If you ask 50 different people how long the effects of cannabis last, you will probably get 50 different answers. It can be a problem to determine how long a patient who uses the medicine for medical purposes will remain disabled.
A new meta-analysis of 80 papers reduced this time frame. Depending on factors such as how the marijuana is consumed and how strong it is, the user can be harmed for between three and ten hours.
This information can help provide counseling information to patients, help recreational users make better decisions about performing tasks such as managing after cannabis use, and can help update laws to better reflect the reality of cannabis disability .
“THC can be detected in the body weeks after cannabis use, while it is clear that impairment lasts much shorter,” explained psychopharmacologist Iain McGregor of the University of Sydney (USYD) in Australia.
“Our legal framework is likely to catch up and, as with alcohol, focus on the interval when users are at greater risk to themselves and others. Prosecution solely on the basis of the presence of THC in blood or saliva is clearly unfair.”
A meta-analysis is what it sounds like: an overview and analysis of the relevant scientific literature, after which the results are crossed to arrive at a finding based on a wider range of methodologies and topics (in this case people) than what can be covered in a single study.
For this research, a team led by USYD nutritionist Danielle McCartney referred to 80 separate studies on the attenuation of tetrahydrocannabinol (THC), the intoxicating substance in cannabis, which performed the first meta-analysis of its kind.
From the 80 papers, the team studied 1 544 “performance outcomes” of people who took marijuana; that is, how these people perform at different stages during management or similar cognitive tasks after consuming cannabis.
How long the attenuation lasted depends on three main factors: how strong the dose of THC is; whether the cannabis has been inhaled or taken orally in the form of food, capsules or drops; and whether the person was an occasional regular cannabis user.
“Our analysis indicates that shortening can take up to 10 hours if high doses of THC are consumed orally. However, a more typical duration of shortening is four hours, when lower doses of THC are consumed by smoking or evaporation and simpler tasks are undertaken.” Said McCartney.
“This shortening can last up to six or seven hours if higher doses of THC are inhaled and complicated tasks, such as driving, are assessed.”
Interestingly, regular cannabis users can build up a tolerance and perform better on cognitive tasks than occasional users after the same amount of consumption. 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 reach the same level of intoxication as a user.
“We have found that disability among occasional users is sometimes more predictable than ordinary marijuana users. Heavy users show a significant tolerance to the effects of cannabis on management and cognitive functions, while they usually show some degree of disability,” said Thomas Arkell, a behavioral pharmacologist, also explained by USyd. .
The findings suggest that most management-related skills may return within five hours of inhaling cannabis, although this time may vary.
More research needs to be done on these time intervals for regular users to better characterize the effects of THC across the board. However, once this is done, the information could guide legislation, the researchers said.
“Laws should be about road safety, not arbitrary punishment. Since cannabis is legal in an increasing number of jurisdictions, we need an evidence-based approach to drug management laws,” McGregor said.
The research was published in Neuroscience and Biobehavior Reviews.