Fifty years with the Hamilton scales for anxiety and depression. A tribute to Max Hamilton.

From the moment Max Hamilton started his psychiatric education, he considered psychometrics to be a scientific discipline on a par with biochemistry or pharmacology in clinical research. His clinimetric skills were in operation in the 1950s when randomised clinical trials were established as the method for the evaluation of the clinical effects of psychotropic drugs. Inspired by Eysenck, Hamilton took the long route around factor analysis in order to qualify his scales for anxiety (HAM-A) and depression (HAM-D) as scientific tools. From the moment when, 50 years ago, Hamilton published his first placebo-controlled trial with an experimental anti-anxiety drug, he realized the dialectic problem in using the total score on HAM-A as a sufficient statistic for the measurement of outcome. This dialectic problem has been investigated for more than 50 years with different types of factor analyses without success. Using modern psychometric methods, the solution to this problem is a simple matter of reallocating the Hamilton scale items according to the scientific hypothesis under examination. Hamilton's original intention, to measure the global burden of the symptoms experienced by the patients with affective disorders, is in agreement with the DSM-IV and ICD-10 classification systems. Scale reliability and obtainment of valid information from patients and their relatives were the most important clinimetric innovations to be developed by Hamilton. Max Hamilton therefore belongs to the very exclusive family of eminent physicians celebrated by this journal with a tribute.