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

The 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.

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.