thirties3txt

An article by Rosanoff et al. (1934) on the etiology of so-called
schizophrenic psychoses is one of a series of reports on investigations
of twins. Among 1014 twin pairs, cases of dementia praecox
(schizophrenia) were identified in 142 subjects. In the 19 male pairs and
22 female pairs of monozygotic twins, both twins were affected in 10 of
the male pairs and 18 of the female pairs. The total concordance rate
was 68.3 percent, but in female pairs it was 82 percent and in male pairs
only 53 percent.

In 11 pairs of dizygotic twins where both were male, three (27 percent)
both developed schizophrenia. In 42 dizygotic female pairs, seven (17
percent) were both affected. Among 48 pairs of opposite sex twins, five
were both affected. Pairs in which only one twin became schizophrenic,
21 were males and 22 females. Total concordance rate in dizygotic twins
was 14.9 percent. Rosanoff et al. cited Humm's (1932) concordance
rate of 3.1 percent among siblings of schizophrenic patients, and
concluded that the excess among dizygotic twin pairs must be attributed
to factors other than heredity.

Rosanoff et al. observed that hereditary factors were not always present,
and therefore not essential, in the etiology of schizophrenic psychoses.
They found similarity of psychotic manifestations in both of a pair of
monozygotic twins was the exception rather than the rule, and suggested
that though hereditary factors seemed to play an important part their
pathogenic effects were not specific.

A more detailed scrutiny revealed the possibility of separating out a
group of cases that occurred on a basis of "partial decerebration" of
traumatic or infectious origin. In support of this Rosanoff et al. pointed
out that at least five, of the nine monozygotic male pairs in which only
one was affected, had clear-cut evidence of trauma or infection affecting
the central nervous system – one of these was a victim of the influenza
epidemic of 1918-1919. They found the proportion of cases with
traumatic or infectious etiology to be higher in males than females, and
suggested a more marked cerebral vulnerability in males.

Birth trauma was cited by Rosanoff et al. as a probable cause of partial
decerebration. They stressed that slight, unnoticed, and even
unnoticeable traumas were capable of producing decerebration
syndromes that would be manifest only after twenty years or more. In
support of this was the delay after trauma, producing unconsciousness
in childhood, in some of those who later developed schizophrenia.

This paper is available online via:
http://ajp.psychiatryonline.org/cgi/content/abstract/91/2/247