As many as three in 10 patients in a recent study didn't take common drugs in the ways prescribed by physicians, but doctors can improve medication adherence if they have a good relationship and trusting communication with patients.

The study, "Communication and Medication Adherence: The Diabetes Study of Northern California," published Monday in JAMA Internal Medicine, found that doctors could reduce the rate of medication "nonadherence" by forming better relationships with patients.

Patients who felt that their doctors listened to them, had involved them in decisions and gained their trust followed doctors' orders more often and took their drugs as prescribed, the study found. "By supporting doctors in developing meaningful relationships with their patients, we could help patients take better care of themselves," lead author Dr. Neda Ratanawongsa, an assistant professor in the University of California San Francisco Department of Medicine, said in a news release on the study.

Researchers studied questionnaires from 9,377 patients who were taking drugs to lower blood sugar, blood pressure or cholesterol. They looked at survey responses from patients regarding how well they thought their doctors communicated with them and compared those with rates of medication nonadherence, which was determined by measuring delays in refilling prescriptions.

Overall, about 30% of the patients may not have been taking their drugs as prescribed, but that figure dropped 4% to 6% for patients who said their doctor had an established, trusting relationship with the patient. Doctors who were better communicators had better rates of patient medication adherence, even if the communication was not specifically focused on the drugs themselves, the study found.

The study was led by researchers at UCSF, San Francisco General Hospital and Trauma Center, and the Kaiser Permanente Research Division, and it was paid for through grants from divisions of the National Institutes of Health.