Chronic pain is the most common reason people give when they enroll in state-approved medical marijuana programs.

That’s followed by stiffness from multiple sclerosis and chemotherapy-related nausea, according to an analysis of 15 states published Monday in the journal Health Affairs.

The study didn’t measure whether marijuana actually helped anyone with their problems, but the patients’ reasons match up with what’s known about the science of marijuana and its chemical components.

“The majority of patients for whom we have data are using cannabis for reasons where the science is the strongest,” said lead author Kevin Boehnke of the University of Michigan.

California became the first state to allow medical use of marijuana in 1996. More than 30 states now allow marijuana for dozens of health problems. Lists of allowable conditions vary by state, but in general, a doctor must certify a patient has an approved diagnosis.