Surprisingly, according to researchers,, control of type 1 and 2 diabetes "was not significantly improved by free distribution."

It seems like a no-brainer: removing the cost barrier to a prescription drug will improve patient adherence. But, according to a team of Canadian researchers, free drugs won't convince all patients to swallow those pills.

As reported in a recent JAMA article, offering to remove cost barriers to life-saving prescription drugs does encourage adherence. The researchers identified more than 700 Canadian patients who said they had stopped taking their drugs as prescribed due to the cost to them. The team divided the groups into two, one receiving their drugs for free, the other continuing to access their drugs as they had previously. After one year, they checked in with the groups to review adherence to the 128 drugs on the list.

Related: The connection between medication adherence and health care savings

Adherence did increase for those relieved of their personal investment–but perhaps not as much as might have been expected. Within the free-drug group, acceptable adherence was identified in 38 percent of those in the group, compared to 27 percent among those still paying for their drugs.

The team also reviewed health outcomes, where mixed results were reported. For instance, control of type 1 and 2 diabetes "was not significantly improved by free distribution;" "low-density lipoprotein cholesterol levels were not affected," but a reduction in systolic blood pressure did emerge. In part, the researchers suggested, the lack of better health outcomes could mean the patients were not receiving the right drugs. But, they noted, that is a topic for someone else's study.

Overall, the report applauded the 11.6 percent increase in adherence among those chronic non-adherers who got their drugs for free. "Participants receiving free medicine distribution were more likely to report being able to make ends meet; the hypothesis that medicine access allows people to afford other necessities can be tested in future studies."

As for the still-considerable lack of adherence among the group, the team concluded that removing the copay/deductible barrier is just one step toward addressing the issue. The team acknowledged the study's limits, which did not include a prior adherence baseline for the patients. Additionally, the report said, "Unblinded allocation to free medicine distribution could have motivated participants to exaggerate their adherence or resulted in different care from clinicians."

Read more: 

• How pharma is teaming up to improve patient adherence and cut costs
• Doctors propose new diagnosis: 'Unable to pay for prescriptions'
• 10 cities paying the most for prescription drugs