---
title: "John Ioannidis"
chunk: 1/5
source: "https://en.wikipedia.org/wiki/John_Ioannidis"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:42:37.127948+00:00"
instance: "kb-cron"
---

John P. A. Ioannidis ( EE-ə-NEE-diss; Greek: Ιωάννης Ιωαννίδης, pronounced [i.oˈanis i.oaˈniðis]; born 21 August 1965) is a Greek-American physician-scientist, writer, and Stanford University professor who has made contributions to evidence-based medicine, epidemiology, and clinical research. Ioannidis studies scientific research itself (meta-research) primarily in clinical medicine and the social sciences.
He has served on the editorial board of over twenty scientific journals including Journal of the American Medical Association (JAMA), Journal of the National Cancer Institute (JNCI), and The Lancet.
Ioannidis's 2005 essay "Why Most Published Research Findings Are False" was the most-accessed article in the history of Public Library of Science (PLOS) as of 2020, with more than three million views.
Ioannidis was a prominent opponent of lockdowns during the COVID-19 pandemic, and he has been accused of promoting conspiracy theories about COVID-19 policies and public health and safety measures.

== Early life and education ==
Born in New York City in 1965, Ioannidis was raised in Athens, Greece. He was valedictorian of his class at Athens College, graduating in 1984, and won a number of awards, including the National Award of the Greek Mathematical Society. He graduated in the top rank of his class at the University of Athens Medical School (1990), then attended Harvard University for his medical residency in internal medicine. He did a fellowship at Tufts University for infectious disease and received a PhD in biopathology at the University of Athens (1996).

== Career ==
He is a very highly cited medical researcher, with an h-index of 278 on Google Scholar in January 2026.
From 1998 to 2010, Ioannidis was chairman of the Department of Hygiene and Epidemiology, University of Ioannina School of Medicine. In 2002, he became an adjunct professor at Tufts University School of Medicine. He has also been president of the Society for Research Synthesis Methodology.
He holds four academic appointments at Stanford University: Professor of Medicine, Professor of Epidemiology and Population Health, Professor (by courtesy) of Statistics and Professor (by courtesy) of Biomedical Data Science. He is director of the Stanford Prevention Research Center, and co-director, along with Steven N. Goodman, of the Meta-Research Innovation Center at Stanford.

== Research ==

Ioannidis's 2005 paper "Why Most Published Research Findings Are False" is the most downloaded paper in the Public Library of Science. In the paper, Ioannidis says that most published research does not meet good scientific standards of evidence. Ioannidis has also described the replication crisis in diverse scientific fields including genetics, clinical trials, neuroscience, and nutrition. His work has aimed to identify solutions to problems in research, and on how to perform research more optimally. In a series of five papers about research published in The Lancet and titled "Research: increasing value, reducing waste", Ioannidis co-authored papers discussing prioritization, transparency and the assessment of existing evidence when making decisions for the funding of research so that they meet the needs of users of research and examining how to correct weaknesses in research design, methods, and analysis by involving experienced statisticians and methodologists and avoiding stakeholders with conflicts of interest.
Ioannidis's research at Stanford focuses on meta-analysis and meta-research – the study of studies. Thomas Trikalinos and Ioannidis coined the term Proteus phenomenon to describe tendency for early studies on a subject to find larger effect than later ones.
He was an early and influential public critic of Theranos, the now-fallen Silicon Valley blood test startup that at its height was valued at up to $9 billion. He criticized it for "stealth research" that it had not made available for other scientists to review.

=== Meta-research ===
Ioannidis has defined meta-research to include "thematic areas of methods, reporting, reproducibility, evaluation, and incentives (how to do, report, verify, correct, and reward science)". He has performed large-scale assessments of the presence of reproducible and transparent research indicators such as data sharing, code sharing, protocol registration, declaration of funding and conflicts of interest in biomedical sciences, social sciences, and psychology. He has led or co-led efforts to define and improve reproducibility in science, e.g. computational reproducibility, and to reduce research waste in study design, conduct, and analysis.  Ioannidis has co-authored the Manifesto for Reproducible Science, an eight-page document illuminating the need to fix the flaws in the current scientific process and mitigate the "reproducibility crisis" in science.
In "Why Most Published Research Findings are False" (2005), Ioannidis focused on why most published research findings cannot be validated. In a later paper on PLOS Medicine (2014), he discusses what can be done to improve this situation and make more published research findings to be true and in a third paper (2016) he showed why clinical research in particular is usually not useful and how this can be amended. In the first of the three PLOS papers he stated that "a research finding is less likely to be true when the studies conducted in a field are smaller; when effect sizes are smaller; when there is a greater number and lesser preselection of tested relationships; where there is greater flexibility in designs, definitions, outcomes, and analytical modes; when there is greater financial and other interest and prejudice; and when more teams are involved in a scientific field in chase of statistical significance". In the second paper, he discussed solutions: "adoption of large-scale collaborative research; replication culture; registration; sharing; reproducibility practices; better statistical methods; standardization of definitions and analyses; more appropriate (usually more stringent) statistical thresholds; and improvement in study design standards, peer review, reporting and dissemination of research, and training of the scientific workforce". In the third paper, he proposed eight features that are important for useful clinical research: problem base, context placement, information gain, pragmatism, patient-centeredness, value for money, feasibility, and transparency. Ioannidis was invited to present his findings as a keynote speaker at the "Evidence Live 2016" conference, hosted jointly by the Centre for Evidence-Based Medicine (CEBM) at the Nuffield Department of Primary Care Health Sciences, University of Oxford and the BMJ.