Known Unknowns: The Difference Between Science and Scientism in Psychiatry

Ronald W. Pies, MD


May 05, 2016

In This Article

Interpreting Your Way to the Truth

When I was a second-year psychiatry resident in the 1980s, a period when CT technology was relatively new, I once had occasion to go over a scan of the brain with the chief resident in radiology. After discussing the findings with the resident, I asked whether the scan was read as normal. He glared at me with withering contempt. "It wasn't read as normal," he growled, "it is normal!"

He was expressing a common but mistaken understanding of science and medicine—namely, that objective, certain knowledge is possible, apart from acts of interpretation. Some critics of psychiatry make the same mistake when they claim to know what the research literature on schizophrenia or depression "really shows." In fact, the literature itself "shows" nothing, absent its often contested interpretation.

No, I'm not advancing the postmodernist notion that "there is no truth," or that all "narratives" are of equal value. I am arguing that genuine science produces only tentative and provisional knowledge, always subject to revision according to new evidence—and new interpretations.

Cultivating Consensus

Speaking of new interpretations, here's a quick quiz: Which medical specialty decides what is or isn't pathological by taking a vote on the question? Which medical specialty is frequently roiled by controversy as to what is or isn't "normal"? If you answered psychiatry, you would be only partly right. You could easily have answered oncology and been equally correct.

This point was recently driven home when an international panel of medical experts decided that "a type of tumor that was classified as a cancer is not a cancer at all."[1] As reported in JAMA Oncology, the reclassified tumor is a lump in the thyroid that is completely surrounded by a fibrous capsule.[2] The nuclei of the tumor cells resemble those of cancer cells, but the tumor is completely contained and treatment is unnecessary. What was once classified as a papillary thyroid carcinoma is now called a "noninvasive follicular thyroid neoplasm with papillary-like nuclear features," or NIFTP. Poof—no more thyroid cancer!

Of note, although the majority of the panel was composed of pathologists, one member was a psychiatrist, "who knew the impact a cancer diagnosis could have"[1] on vulnerable patients—an instance in which an ostensibly objective and scientific decision was actually influenced by overtly subjective considerations.

To be sure, the vote that decided the matter was not capricious or arbitrary, but instead based on careful follow-up of several hundred cases of supposed thyroid cancer. The finding was clear: None of the patients whose tumors remained encapsulated had any evidence of cancer after 10 years. The panel therefore shifted from using "nuclear features" to "the presence of invasion" as the criterion for cancer. This change may well prevent unnecessary and potentially harmful treatment, but the decision itself represents a clear exercise in interpretation and judgment.

On one level, it is clear that psychiatry and oncology are not comparable fields, because the "sensory data" each discipline deals with are quite different. Psychiatrists, for the most part, process words, gestures, and behaviors. Oncologists, to oversimplify, generally process lumps, labs, and slides.

Yet these interspecialty differences may conceal important similarities. Psychiatrists also process observable physical data ("signs"), such as weight loss and psychomotor slowing or agitation, whereas oncologists must deal with the often devastating emotional reactions of their patients. Furthermore, within their respective provinces of perception, both psychiatrists and oncologists engage in acts of interpretation that are based on ever-changing empirical data.

For example, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) made the rather radical decision to eliminate all the traditional subtypes of schizophrenia—paranoid, disorganized, catatonic, and so on. This came as something of a surprise for many of us, but the decision was based on considerable empirical evidence. As Dr Rajiv Tandon has noted, "these subtypes have limited diagnostic stability, low reliability, poor validity, and little clinical utility."[3]

Now, one can argue—and many have—that numerous DSM-5 diagnoses lack validity, based on the most rigorous validity criteria developed by Robins and Guze.[4] But the process of investigation and interpretation that goes on in psychiatry is fundamentally the same as in general medicine, even though the objects of investigation may be quite different.