Cell phone use and texting while driving have been listed as the top causes of distracted driving in a new report released Thursday from the Governors Highway Safety Association (GHSA), which summarized distracted driving research from more than 350 scientific papers published between 2000 and 2011.

The report found that up to 25 percent of all car crashes are associated with cell phone use, though one study included in the GHSA’s review estimated that just 3 percent to 4 percent of crashes were linked to drivers distracted by their cell phones.

The GHSA shied away from estimating how much cell phone use and texting increased a driver’s crash risk, saying “the only definite conclusion is that hand-held cell phone use

increases crash risk to some extent.” Texting while driving was found to be more risky than placing a call.

The GHSA also said there was “no conclusive evidence” that hands-free cell phone use was less risky than hand-held use.

“Despite all that has been written about driver distraction, there is still a lot that we do not know,” GHSA Executive Director Barbara Harsha, who oversaw the report’s development, said in a statement. “Much of the research is incomplete or contradictory. Clearly, more studies need to be done addressing both the scope of the problem and how to effectively address it.”

Between 15 percent and 25 percent of all car crashes are associated with distracted driving, according to the report.

Distracted driving is a widespread problem. The report found that more than half of all drivers “engaged in some form of secondary task” while driving, and nearly a quarter were distracted in risky driving situations, such as near intersections or in heavy traffic.

Laws banning drivers from using their cell phones while driving were found to have had a limited, short-term effect. The bans cut hand-held cell phone use by about half when they were first implemented, but cell phone use subsequently increased. The GHSA reported that there was no evidence that cell phone or texting bans have reduced crashes and found that the laws are difficult to enforce.

Nine states and the District of Columbia have banned all drivers from using hand-held cell phones while driving. Cell phone use by novice drivers is prohibited by 30 states and the District of Columbia.