(CNN) Out-of-pocket costs for Americans with neurologic conditions have risen so rapidly over 12 years, a new study says, that doctors need better access to drug price information "to minimize patient financial burden."

"Out-of-pocket costs have risen to the point where neurologists should be able to consider the potential financial burden for the patient when prescribing medication, but they do not have this information available to them," said Dr. Brian C. Callaghan, the study's lead author and assistant professor of neurology at the University of Michigan

A decade ago, Callaghan said, doctors hardly considered out-of-pocket costs because they were "close to $0 and mostly co-pays." But that has changed.

"If you're not thinking about it," he said, "you're really doing your patient a disservice."

The problem is "that physicians don't even know whether it's cheap for you or expensive for you," he said, "and we know that high out-of-pocket costs affect how often patients end up taking medicines. So we're going to have situations where they probably are going to have worse outcomes because they're not taking medicines based on costs and other factors."

Using a large health care claims database, researchers examined out-of-pocket costs for more than 912,000 Americans with dementia, epilepsy, multiple sclerosis, peripheral neurophathy or Parkison's disease over 12 years. These patients were privately insured and took at least one neurologic medication.

Out-of-pocket costs were up for each disorder, but MS patients have seen the sharpest rise.

Just how much have costs gone up? For MS medications, out-of-pocket costs were $15 a month in 2004; by 2016, they were $309 a month, the study found. And there's no sign of costs going down anytime soon.

"It is likely out-of-pocket costs will continue to increase," Callaghan said.

That's because of new high-priced medications in the pipeline, he said.

The costs were even more dramatic for people with high-deductible plans, the researchers found. For instance, in 2016, MS patients in high-deductible plans paid $661 a month, compared with $246 a month for those not in high-deductible plans.

The researchers also found that 5% of MS patients paid $9,855 or more over two years. With a median household income in 2016 of $53,039, Callaghan said, "that's a significant chunk of their median household income."

The costs have been gradually rising over the years, he said, but the data showed significant jumps in out-of-pocket costs beginning in 2015 and continuing in 2016.

"That was probably the most surprising thing," Callaghan said.

Dr. Nicholas Johnson , vice chairman of research and associate professor in the Department of Neurology at Virginia Commonwealth University, called the research "an incredible paper" that sheds light on a vital issue for all Americans. He said he and others across the field of neurology have been increasingly concerned about "the escalating prices of neurological therapeutics across the board."

"What I think this paper really illustrates is the financial toxicity that comes with these drugs is just incredible," said Johnson, who was not involved in the research. "We need to be doing a better job as physicians ... to think to ask patients about the financial side effects of the medicines they're taking.

"This paper really does illustrate not only that we as practitioners should be asking about, but it also illustrates again the financial toxicity and the risks that it places on our patients."

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The study did not name the drugs examined in the research but said they were the "top five most commonly prescribed medications for each condition as well as any other known high-cost drugs."

The study was supported by the American Academy of Neurology.

Dr. Ralph Sacco, the president of the association, said the research "provides important information to help us better understand how these problems can directly affect our patients."