New Study Shows Cannabis May Weaken a Person’s Driving Ability

A new study finds that cannabis may weaken a person’s driving ability for up to four hours.

There are many things cannabis use can be good for, including pain and insomnia relief. However, a new study says driving while under its influence could be detrimental to a person’s ability to operate a vehicle. In a recent report that was published in the JAMA Psychiatry, researchers said drivers were not able to return to normal functionality until 4.5 hours later after use.

“Although performance was improving at 3.5 hours, recovery was not fully seen until 4.5 hours post smoking,” says researchers from the Center for Medicinal Cannabis Research at the University of California San Diego. The team of researchers analyzed 191 regular cannabis users and found smoking led to a decline in simulated driving scores.

Each study participant was given a placebo cigarette or a cannabis cigarette that included 5.9 % of 13.4 % levels of delta-9-tetrahydrocannabinol (THC), which is the psychoactive compound in cannabis. A great decline in Composite Drive Scores (CDS) was seen at the 25-minute mark of the simulated driving test.

Some of the things researchers tested were the participants’ ability to pay attention to different tasks. Researchers noticed swerving in lanes when participants were asked to follow a lead car. Researchers also said drivers were hesitant to drive right after smoking.

“Although users in the THC group felt impaired and were hesitant to drive at 30 minutes, by 1 hour-30 minutes they believed the impairment was wearing off and were more willing to drive. This was despite their performance not significantly improving from the 30-minute point,” wrote Senior author Thomas Marcotte, PhD, co-director of CMCR and a professor of psychiatry at UC San Diego School of Medicine in the University news release.