Marijuana dispensary
Products are displayed for sale at Oregon's Finest, a marijuana dispensary in Portland, Oregon, on October 4, 2015 Josh Edelson/AFP/Getty Images

A new study found that states with legalized recreational use of marijuana have an increase in accident insurance claims. The study, conducted by the Highway Loss Data Institute looked at three states: Colorado, Oregon and Washington.

According to the study, the number of vehicle collisions reported to insurance companies in the three states is at least 3% higher than what would have been expected if marijuana had not been legalised. However, the study did not indicate whether the increase in collisions were directly caused by drivers who were under the influence of marijuana.

"We're concerned about what we're seeing," Matt Moore, the institute's senior vice president, said. "We see strong evidence of an increase crash risk in states that have approved recreational marijuana sales."

CNBC noted that the study also did not look at highway fatality rates in states where marijuana use is legal.

The institute compared collision claims before and after legalisation, with collision claim rates of comparable states where marijuana is still illegal, to determine whether collision rates are higher than they would be if recreational use was still illegal.

The study found that collision claims following legalisation are up 16% in Colorado, 6.2% in Washington and 4.5% in Oregon.

"Colorado has had legal pot sales the longest and it is showing the greatest effect," Moore said. "Meanwhile, Oregon has had pot sales for the shortest amount of time, so its increase is the lowest, but that could change over time."

The study was released as more states consider legalising marijuana sale, CNBC reported.

While questions regarding marijuana use and auto collisions have emerged in states that have approved of cannabis for recreational use, they are difficult to answer. CNBC reported that field sobriety tests to check drivers specifically for marijuana do not exist.

Moore also noted that drivers who test positive for having THC often have alcohol in their systems too. "We're concerned about impaired driving in general," Moore said. "Marijuana just layers on top of other impairments like alcohol."

Eight states, as well as Washington DC, have legalised recreational marijuana sales.