Center for Research in Clinical Psychology, University of Oslo, 0315 Oslo 3, Norway
It is well known that dysphoric clinical conditions rarely manifest themselves as purely depressive or anxious entities. More common is a changing mixture of depressive and anxiety symptoms. The question then arises: Is the mixed anxiety-depressive disorder a phenotypic variant of anxiety or depressive disorders or is it a separate disorder in itself? A way to answer this question is to apply family-genetic methods and look for a genetic connection. Another way is to see whether the same or different environmental factors are involved in the development of the pure and the mixed conditions. In this article I will do both. The data presented in this article stem from a nationwide study of twins treated by all the Norwegian psychiatric institutions (1). Both partners in 299 sets of twins were personally interviewed. The case sum­maries were independently diagnosed by three judges. The agreement was high. Two of three judges agreed upon the diagnosis of anxiety neurosis in 95% of the cases and in 87% of the cases for neurotic depression. Seventy-six index twins received a diagnosis of anxiety neurosis and 74 a diagnosis of neurotic depression. However, the overlap of symptoms between the two diagnostic groups was high (Table 1). Consequently a discriminant analysis was performed, and Table 2 shows the symptoms that discriminated most strongly between anxiety neurosis and neu­rotic depression. The index twins were classified in three groups by means of the discriminant function, one pure anxiety neurosis group, one mixed anxiety-depressive group, a nd one pure neurotic depression group, each consisting of 50 index twins (2,3). The cotwins with anxiety neurosis and neurotic depression were also classified according to the discriminant function with the same cutting points and the results are presented in Table 3. Table 3 shows that the concordance for the same disorder as well as the two Wier affective disorders is much higher in cotwins of MZ index twins with pure anxiety neurosis compared to cotwins of DZ twins. On the other hand, the

concordance rate is the same for MZ and DZ cotwins of index twins with mixed anxiety-depression and pure neurotic depression. This indicates that pure anxiety neurosis is influenced by genetic factors, but not mixed anxiety-depression and neurotic depression. Furthermore, the concordance, both for MZ and DZ twins, is lower in twin pairs in which the index twin has mixed anxiety-neurosis than in twin pairs in which the index twin has pure neurotic depression. This result indicates that common environmental variance, for instance, family features in childhood, is more important in the development of pure neurotic depression, whereas unique environmental variance, for instance, stress in adulthood, is more important in the development of mixed anxiety-depression. I will now show some results that indicate that this is also true. Table 4 shows that to have lost their mother and/or father by death is far more frequent among index twins with pure neurotic depression than in the other affective disorder groups. Also, moving in childhood has happened more often among index twins with pure neurotic depression and mixed anxiety-depression than among index twins with pure anxiety neurosis. Childhood trauma seems thus to be frequent among index twins with pure neurotic depression, and in­frequent among index twins with pure anxiety neurosis. Table 5 indicates that to be never married is more frequent among probands with mixed anxiety-depression, to have lost the spouse by divorce or death is more frequent among probands with pure neurotic depression, whereas to be still married to the first spouse is most frequent among index twins with pure anxiety neurosis. Perhaps these results say something about the pure anxious person’s dependency, the pure neurotic person’s experiences of loss, and the mixed anxiety-depression person’s more frustrating adult life. Finally, Table 6 shows that pure anxiety neurosis is frequently elucidated by pregnancy and childbirth among women, and mixed anxiety-depression and
pure neurotic depression by all kinds of loss or threats of loss, troubles with fiance(e) or spouse, divorce, death of spouse, children, and/or parents. To sum up, genetic factors seem to be involved in the development of pure anxiety neurosis, but not mixed anxiety-depression and pure neurotic depression. Childhood factors, especially loss, seem to be important in the development of pure neurotic depression. There are also indications that adult life may be more




frustrating for people with mixed anxiety-depression. All in all, pure anxiety neurosis seems to be a clearly separate condition, whereas mixed anxiety-depres­sion seems to have an etiology similar to pure neurotic depression. Thus it might be advisable to diagnose the conditions with mixed anxious-depressive symptoms together with neurotic depression and not with anxiety neurosis.

REFERENCES
1. Torgersen, S. (1983): Br. J. Psychiatry, 142:126-132. 2. Torgersen, S. (1985): Br. J. Psychiatry, 146:530-534. 3. Torgersen, S. (1985): Acta Psychiatr. Scand., 71:304-310.

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