Diagnostic Validity Revisited

"Dimensionality by itself tells us very little about what exists in nature. In fact, almost everything in biology varies dimensionally. Hypertension, diabetes, osteoporosis, and most autoimmune diseases all exist along continua. Yet they remain valid medical constructs because they describe genuine syndromes with characteristic features, courses, and biological correlates. Variation across a spectrum does not preclude the existence of meaningful categories. In much of medicine, continuous variation and categorical distinction coexist."

"The fact that symptoms covary or cluster dimensionally does not settle the question of what actually exists in the world. What matters for diagnosis is whether our categories correspond to coherent patterns that exhibit stability, distinctiveness, and some degree of predictive utility. This is the essence of what Robins and Guze (1970) attempted to formalize more than 50 years ago when they proposed a set of criteria for disease validation."

Dimensionality alone cannot determine what exists in nature; many biological conditions vary continuously yet remain valid medical constructs. Hypertension, diabetes, osteoporosis, and most autoimmune diseases exist along continua while retaining coherent features, courses, and biological correlates. Continuous variation and categorical distinction often coexist in medicine. In psychiatry, symptom covariance across dimensions does not resolve ontology. Diagnostic validity depends on whether categories map onto stable, distinctive, and predictively useful patterns. Robins and Guze's validation criteria provide a pragmatic truth-tracking framework for assessing psychiatric diagnoses. Emphasis should remain on whether diagnoses correspond to real, useful syndromes.

Read at Psychology Today