Psychiatrische Untersuchungen an Einer Serie Von Zwillingen. (Psychiatric Research on a Series of Twins.): By Erik Essen-Moeller. Copenhagen: Ejnar Munksgaard, 1941. 200 pp.

The material on which this study is based comprises sixty-nine pairs of twins of the same sex. It forms a complete series in the sense that of a group of ten thousand patients all the twins of the same sex about whom data could be gathered and whose partners reached adulthood were included. This completeness gives the results of the investigation greater conclusiveness than

if a selection of striking similarities among twins, or of otherwise 'interesting' case material had been made. Forty-eight pairs were probably dizygotic, and twenty-one pairs probably monozygotic. The case histories of the monozygotic pairs are presented in greater detail, while the others are briefly described, and only occasionally used to elucidate certain points by way of comparison.

The study of twins has been of interest in psychiatry to determine the relative importance of heredity and environment; it can also contribute towards a better insight into whether an anlage is dominant or recessive. Also, it may be helpful to clarify nosological questions. The author predominantly utilizes this third approach. He attempts to find out to what extent seemingly different syndromes and symptoms may be the manifestation of the same anlage.

Limiting this discussion of the author's results to one group of cases, of seven schizophrenic twins none of the partners had a markedly schizophrenic psychosis, and only one can be considered bordering on a schizophrenic psychosis. However, four of the partners had psychoses of another type: depressions ending in recovery without demonstrable defect. But in three of these partners some transitory symptoms could be observed that remind one more or less distinctly of schizophrenic symptoms. Therefore, it seems more important to the author to determine whether symptoms of a type can be observed, than whether or not they appear as part of a true schizophrenic psychosis.

In all the seven pairs both partners were to a certain extent characterologically abnorm