Applied psychometrics in clinical psychiatry: the pharmacopsychometric triangle

Objective: To consider applied psychometrics in psychiatry as a discipline focusing on pharmacopsychology rather than psychopharmacology as illustrated by the pharmacopsychometric triangle. Method: The pharmacopsychological dimensions of clinically valid effects of drugs (antianxiety, antidepressive, antimanic, and antipsychotic), of clinically unwanted effects of these drugs, and the patients' own subjective perception of the balance between wanted and unwanted effects are analysed using rating scales assessed by modern psychometric tests (item response theory models) Results: Symptom rating scales fulfilling the item response theory models have been shown to be psychometrically valid outcome scales as their total scores are sufficient statistics for demonstrating dose-response relationship within the various classes of antianxiety, antidepressive, antimanic or antipsychotic drugs. The total scores of side-effect rating scales are, however, not sufficient statistics, implying that each symptom has to be analysed individually. Self-rating scales with very few items appear to be sufficient statistics when measuring the patients' own perception of quality of life. Conclusion: Applied psychometrics in psychiatry have been found to cover a pharmacopsychometric triangle illustrating the measurements of wanted and unwanted effects of pharmacotherapeutic drugs as well as health-related quality of life.