It’s hard to resist looking your symptoms up online. But try harder: Not only will your internet search scare you more often than not, it’s also wrong… a lot.

Since it launched in 2001, Wikipedia has become THE reference source. But according to a new study comparing several Wikipedia articles about medical conditions with peer-reviewed research papers, you should speak with your doctor and not take Wikipedia’s word for it: The site contradicted medical research 90 percent of the time.

To evaluate the online encyclopedia’s accuracy, a team led by Robert Hasty from Campbell University looked up the top 10 most costly conditions (in terms of public and private expenditure) in the U.S. These are heart disease, cancer, mental disorders, trauma-related disorders, osteoarthritis, chronic obstructive lung disease/asthma, hypertension, diabetes, back problems, and hyperlipidemia (high blood cholesterol).

They printed out the corresponding Wikipedia entries on April 25, 2012. Two investigators reviewed each article and identified all the assertions made in it. Then to fact-check each implication and statement, the reviewers conducted a literature search to see if each assertion was supported by evidence in peer-reviewed sources through UpToDate, PubMed, or Google Scholar.

They found that nine out of 10 Wikipedia articles contained “many errors.” Looks like trauma-related disorders — or its corresponding Wikipedia entry, concussions — was the only one that didn’t contain statistically significant discordance with scientific studies.

Wikipedia ranks sixth globally, based on internet traffic. All users can edit the information, which of course raises concerns about the reliability of its information. That’s particularly worrisome because up to 70 percent of physicians and medical students admit using Wikipedia as a reference, a recent study found.

“While Wikipedia is a convenient tool for conducting research,” Hasty tells BBC, “from a public health standpoint patients should not use it as a primary resource.”

The work was published in the Journal of the American Osteopathic Association last month.