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How people with mental illness get left out of medical research studies

One of the enduring challenges of evidence-based medicine is that the characteristics of people who participate in clinical trials can differ markedly from those of patients who ultimately access the treatment which the trial evaluates. One of the many reasons this occurs is that researchers often exclude patients with certain characteristics from participating in clinical trials.  In a new study in Journal of Psychiatric Research, my colleagues Laura Roberts, MD; Janet Blodgett, and I examine a particular population to whom this occurs: People with mental health and/or substance use disorders.

If scientists are to live up to their laudable commitment to sharing the benefits of health research with all citizens, they'll have to more consistently include people with psychiatric problems in studies

In a sample of 400 highly-cited randomized trials across 20 common chronic disorders, we found that half had eligibility rules that prevented people with psychiatric problems from enrolling.   Those disease research areas with high rates of reported psychiatric exclusion criteria in clinical trials included low back pain (75 percent), osteoarthritis (57 percent), COPD (55 percent), and diabetes (55 percent).  People with conditions such as depression, anxiety disorders, alcohol problems and schizophrenia thus may face some added risk when they seek health care: People like them were often left out of the research that tells doctors what medical treatments work.

The study also raises questions about whether some clinical trials make much of a contribution to knowledge. For example, now that psychiatric and other substance use problems are virtually normative among smokers, what is the point of smoking cessation studies that continue to exclude the very populations that do most of the smoking?

Including people with psychiatric problems in medical research may require extra resources for researchers (e.g., people with serious mental illness may be harder to follow up) or pose other challenges in completing clinical trials. But if scientists are to live up to their laudable commitment to sharing the benefits of health research with all citizens, they'll have to meet these challenges and more consistently include people with psychiatric problems in medical research studies.

Addiction expert Keith Humphreys, PhD, is a professor of psychiatry and behavioral sciences at Stanford and a career research scientist at the Palo Alto VA. He has served in the past as a senior advisor in the Office of National Drug Control Policy in Washington, DC. He can be followed on Twitter at @KeithNHumphreys.

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