For accuracy, brain studies of complex behavior require thousands of people

Scientists rely on brainwide association studies to measure brain structure and function — using brain scans — and link them to mental illness and other complex behaviors. But a study by researchers at Washington University School of Medicine in St. Louis and the University of Minnesota shows that most published brainwide association studies are performed with too few participants to yield reliable findings.
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As brain scans have become more detailed and informative in recent decades, neuroimaging has seemed to promise a way for doctors and scientists to “see” what’s going wrong inside the brains of people with mental illnesses or neurological conditions. Such imaging has revealed correlations between brain anatomy or function and illness, suggesting potential new ways to diagnose and treat psychiatric, psychological and neurological conditions. But the promise has yet to turn into reality, and a new study explains why: The results of most studies are unreliable because they involved too few participants.