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Latest findings on Parkinson’s disease and caffeine offer an important lesson on how science works

“Our core finding is that caffeine cannot be recommended as therapy for movement symptoms of Parkinson’s disease,” said Dr. Ronald Postuma, a neurologist.

Dr. Ronald Postuma: "Our core finding is that caffeine cannot be recommended as therapy for movement symptoms of Parkinson's disease.”
REUTERS/Eric Vidal

Five years ago, neurologists at McGill University reported that taking daily caffeine capsules (the equivalent of about three cups of coffee a day) appeared to improve some of the debilitating involuntary movements — tremor, slowed movement, rigid muscles — that are associated with Parkinson’s disease.

But as the authors of the study made clear at the time, the findings came with some important caveats. Most notably, the study had involved just 61 people, and its participants had taken a caffeine capsule for only six weeks. Also, the benefits from the caffeine were quite modest compared to those offered by levodopa, the standard drug treatment for Parkinson’s.

A larger, longer study was needed before any firm conclusions could be made about caffeine’s benefits, the McGill researchers stressed.

Well, those neurologists recently published a follow-up study — one that involved twice as many people with Parkinson’s (121) and a longer time period (up to 18 months). As before, half of the study’s participants were given twice-daily capsules containing 200 milligrams of caffeine. The other half received a placebo.

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This time the researchers found no improvement in movement symptoms among the caffeine-taking participants compared to those on the placebo. Nor was there any difference in quality of life.

“While our previous study showed possible improvement in symptoms, that study was shorter, so it’s possible that caffeine may have a short-term benefit that quickly dissipates,” said Dr. Ronald Postuma, a neurologist and the study’s lead author, in a released statement. “Regardless, our core finding is that caffeine cannot be recommended as therapy for movement symptoms of Parkinson’s disease.”

Lessons for health consumers

The findings are disappointing, of course, but important nevertheless. For, as Dr. Michael Joyce, a multimedia producer for the Minnesota-based, points out in a recent column, they teach us some important lessons about how we need to consume our health news.

“This is how science progresses,” Joyce writes. “It’s not so much about clear-cut answers as it is about constantly questioning. In this case, the 2012 results were promising for a ‘positive’ effect on a disease that sorely needs some good news. But, the researchers … were not satisfied and needed to know if these results were verifiable and reproducible. It ends up they were not.”

“Although that ‘negative’ result may not feel as optimistic or impactful as the previous ‘positive’ result, it’s still important information,” he adds. “It’s not only more accurate information, but it will help focus further research.”

Yet, stresses Joyce, we are much more likely to hear about positive scientific results than negative ones.

“When medical journals, academic PR departments, or news organizations avoid publishing negative results — presumably because they lack the allure or gravitas of positive results — they’re not just revealing ignorance of the scientific method, but are also severely compromising public opinion and discourse by providing incomplete information,” he explains. “People make decisions about their health based on what they read in the news; if that news is slanted toward positive findings, the public doesn’t have a solid foundation for making good choices.”

A disconnect

Remarkably, that was true even of Postuma’s own patients.

“I always try to include caveats and limitations [when releasing information on his scientific research],” Postuma told Joyce.  “And most of the reporters included them and were accurate. But, nonetheless, all my patients started drinking coffee. Even when I told them these were just preliminary findings. That surprised me.” 

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“This one doesn’t fall on the reporters,” he added. “Because between what they write, and what goes into people’s heads, there’s often a disconnect. Readers often seem to want to remember one or two things, then our warnings and caveats disappear, and they select what becomes fact in their brain.”

A cautionary tale for all of us.

FMI: Postuma’s latest study was published in Neurology. You’ll find an abstract of the study on that journal’s website, but the full study is behind a paywall. Go to to read Joyce’s article on how we are much more likely to hear about “positive” rather than “negative” research findings — and why that matters.