Starting his medical career at the beginning of the evidence based medicine movement, Ioannidis gravitated away from undertaking new research towards assessing the validity of previous research. Systemic inaccuracy emerged consistently at every level, and began to paint the picture that most studies were biased. Uniquely positioned as an expert statistician, Ioannidis carefully assembled a team, which spent a decade exploring the problem before publishing a landmark paper. It concluded:

With natural levels of researcher bias, generally imperfect research techniques, and a common tendency to focus on novel rather than plausible theories, wrong findings will be the norm. At the same time the scientific journals are strongly biased towards publishing the most novel claims and lack effective safeguards for filtering out inaccurate studies.

The paper showed both theoretically and empirically that 80 percent of non-randomized studies (the most common type), 25 percent of the "gold-standard" randomized trials, and nearly 10 percent of the "platinum-standard" large randomized trials were incorrectly executed.

To highlight the inability to weed out bad research, they focused on the 49 most highly regarded and cited research papers published in the past 13 years. Of those, 41% had later been disproved when tested, while 24% hadn't even been retested. Upon further examination, 3 of these studies, which were later firmly disproved, they found scientists were more likely to cite the original inaccurate study, in one case for at least 12 years after it was discredited.

Economics appears to be an underlying cause of the research inaccuracies. A successful scientific career depends upon your research being funded and published. This intellectual conflict of interest motivates scientists to pursue and produce results that will be funded. Scientific journals are naturally biased towards publishing new, exciting research; they rely upon a vetted peer review process that is frequently commandeered by scientists in pursuit of career advancement. Worst of all are drug studies, funded by pharmaceutical companies and commonly corrupted by a much stronger financial conflict of interest.

It thus should come as no surprise that many medications originally shown to be both safe and effective in numerous large randomized control trials were later found to be dangerous. Vioxx, Zelnorm, and Baycol all were taken off the market for safety concerns, while the anti-depressants Prozac, Zoloft, and Paxil are now known to be no more effective than placebos.

Science, by definition, relies upon continual retesting of previous results by other scientists to protect against erroneous conclusions. Yet, this does not occur. In Ioannidis' own words, the "odds that anything useful will survive from any of these studies are poor."

Sources:

http://www.theatlantic.com/magazine...

http://www.plosmedicine.org/article...

www.naturalnews.com/031121_medical_research_fraud.html