If you ask 50 different people how long the effects of cannabis last, you are likely to get 50 different answers. This can be a problem in figuring out how long a patient using the drug for medical purposes will remain impaired.
A new meta-analysis of 80 articles has reduced this time period. Depending on factors such as how the cannabis is consumed and how strong it is, the user may be affected for three to ten hours.
This information can help inform the counseling information given to 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.
“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,” explained psychopharmacologist Iain McGregor of the University of Sydney (USYD) in Australia.
“Our legal frameworks probably need to catch up with this and, as with alcohol, focus on the interval in which users are most at risk for themselves and for others. based on the presence of THC in the blood or saliva is manifestly unfair. “
A meta-analysis is what it seems: a review and analysis of the relevant scientific literature, making cross-references of the results to arrive at a finding based on a wider range of methodologies and topics (in this case, people) that can be addressed. in a single study.
For this research, a team led by USYD nutritionist Danielle McCartney referred to 80 different studies on the deterioration of tetrahydrocannabinol (THC), the intoxicating compound in cannabis, which conducted the first meta-analysis of this. type.
From these 80 studies, the team studied 1,534 “performance results” from people who had taken cannabis; that is, how these people functioned in driving or in equivalent cognitive tasks at various stages after taking cannabis.
The duration of the deterioration depended on three main factors: the strength of the THC dose; whether cannabis was inhaled or taken orally in the form of food, capsules, or drops; and whether the person was an occasional or regular user of cannabis.
“Our analysis indicates that deterioration can last up to 10 hours if high doses of THC are consumed orally. However, the most typical duration of deterioration is four hours, when lower doses of THC are consumed through smoking. or vaporize and simpler tasks are performed. ”McCartney said.
“This deterioration can extend 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 increase tolerance and perform better in cognitive tasks than occasional users after consuming the same amount. Therefore, it is 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 an occasional user.
“We found that impairment is much more predictable in occasional cannabis users than regular cannabis users. Heavy users show significant tolerance to the effects of cannabis on driving and cognitive function, while typically showing some impairment. “, explained behavioral pharmacologist Thomas Arkell, also of USyd. .
The findings suggest that most driving-related skills could return within five hours of inhaling cannabis, although that time may vary.
More research will need to be done on these time intervals for regular users, in order to better characterize the effects of THC in general. Once this is done, however, the information can guide the legislation, the researchers said.
“Laws should be about road safety, not arbitrary punishment. Since cannabis is legal in a growing number of jurisdictions, we need an evidence-based approach to drug driving laws,” he said. said McGregor.
The research has been published in Neurosciences and reviews of biological behavior.