Penrose's law: Methodological challenges and call for data.

The investigation of the relationship between the sizes of the mental health population and the prison population, outlined in Penrose's Law, has received renewed interest in recent decades. The problems that arise in the course of the deinstitutionalization have repeatedly drawn attention to this issue. This article presents methodological challenges to the examination of Penrose's Law and retrospectively reviews historical data from empirical studies. A critical element of surveys is the sampling method; longitudinal studies seem appropriate here. The relationship between the numbers of psychiatric beds and the size of the prison population is inverse in most cases. However, a serious failure is that almost all of the data were collected in countries historically belonging to a Christian or Jewish cultural community. Only very limited conclusions can be drawn from these sparse and non-comprehensive data: a reduction in the number of psychiatric beds seems to be accompanied by increases in the numbers of involuntary admissions and forensic treatments and an accumulation of mentally ill persons in prisons. A kind of transinstitutionalization is currently ongoing. A pragmatic balance between academic epidemiological numbers and cultural narratives should be found in order to confirm or refute the validity of Penrose's Law. Unless comprehensive research is undertaken, it is impossible to draw any real conclusion.