Although evidence-based psychiatry and psychiatric practice are largely dependent on clinical applications of psychometric theory, psychometrics as such (i.e. the field of study concerned with the theory and technique of psychological measurement) is not the favourite field of interest of most psychiatrists. Psychometric theory is neglected in psychiatric training, comprehensive or introductory textbooks with a clinical focus are scarce.

‘Clinical psychometrics’ attempts to fill this gap. As stated on the back cover, it is targeted for everyone who is interested in the origins and development of modern psychiatry and who wants to be familiar with its practical possibilities: how it is possible to compare different individuals with each other; how one may determine the boundary between normal and what is disease; or how one may assess the clinical effect of various forms of treatment available to present day psychiatry. Some (or even profound) knowledge of these issues seems mandatory in the current context of criticism on DSM-5 and efficacy of psychotropics. Diagnoses do not carve nature at its joints and psychotropics (unlike for instance antibiotics) are not magic bullets; therefore, careful clinical and methodologically sound observation (diagnosis and treatment; pharmacopsychology as developed by Emil Kraepelin) is of utmost importance.

In a concise manner, Per Bech describes the history of psychometric theory. The origins of factor analysis, principal component analysis, sufficient statistics, item response theory analysis and effect size statistics are sketched. This is done within their historical context. The importance of great psychologists (e.g. Wilhelm Wundt and Hans Eysenck), psychiatrists (e.g. Emil Kraepelin, Max Hamilton and Pierre Pichot), psychologists/mathematicians (e.g. Karl Pearson, Charles Spearman and Georg Rasch) and even philosophers (e.g. Emmanuel Kant, Bertrand Russell and Ludwig Wittgenstein) are highlighted. By this historical approach, psychometric theory becomes more palpable (of clinical and philosophical interest, not merely a technical detail or nuisance) and personal (not just facts, but also people behind these facts).

Clinical consequences of item response theory analysis are described in more detail under the ‘pharmacopsychometric triangle’: measurement of wanted clinical effect, unwanted clinical effect and patient-related quality of life. This analysis is performed for different psychotropic classes. Clinical consequences of item response theory analysis are further discussed in models of health-related quality of life and stress. In different appendices, covering brief rating scales (e.g. Hamilton Depression Scale, Montgomery–Åsberg Depression Scale, Bech–Rafaelsen Melancholia Scale) psychometric theory is put into practice. In the epilogue (‘Who's carrying Einstein's baton?’), the author gives an account of the psychometric relay race: who is carrying the baton of Kraepelin, Hamilton, Pichot and other giants?

Ambitions of this book/author (cf. back cover) were high, but seem to have been fulfilled. In a thoughtful way, Per Bech takes a thoughtful stance on the use of rating scales in daily psychiatric practice. ‘Clinical psychometrics’ should be a ‘must read’ for psychiatrists (in training) with interest in the clinical, mathematical and philosophical underpinnings of evidence-based psychiatry. For some readers, it will be a pleasurable self-limiting ‘Aha-Erlebnis’. For some readers, it will be the start of a different, more psychometric approach in diagnosis and treatment. For some readers, it could be the beginning of a further quest or participation in the aforementioned relay race, which cannot be run without clinically experienced psychiatrists.