342 H. M. POLLOCK, B. MALZBERG AND R. G. FULLER 



authoritative statement at present of the chance of developing a manic- 

 depressive psychosis in the course of a life time comparable to the expec- 

 tation with respect to all forms of psychoses. But we may make a fair 

 estimate of such a probability by noting that male first admissions with 

 manic-depressive psychoses average 10 per cent of all male first admissions 

 and that female manic-depressives average close to 20 per cent of all female 

 first admissions. Since the expectations of mental disease are 4.7 and 4.4 

 per hundred for males and females respectively, we may estimate the expec- 

 tation of manic-depressive psychoses at roundly 0.5 and 0.9 per hundred 

 for males and females, respectively. 



On this basis we find that the 954 individuals in the families of the 60 

 male patients have an expectation of 6.7 ± 1.7 cases of manic-depressive 

 psychoses. Actually there were only 3 cases. However, as many of the 

 siblings have not passed the age of incidence, we may expect several addi- 

 tional cases to arise among them. Furthermore, there were 7 cases of 

 undiagnosed psychoses, some of which may have been of the manic-depres- 

 sive type. Making allowance for these two facts, we should undoubtedly 

 have to increase the number of cases in the given families. Nevertheless, 

 there is little likelihood that the resulting increase would exceed the expected 

 total in any significant degree. 



In the case of the families of the 95 females however, there is reason for be- 

 lieving that the expected number is exceeded by the actual number. Thus 

 of the 1,423 individuals with known histories, 14 developed manic-depressive 

 psychoses, compared with an expected total of 9.9 ±2.1 cases. There were 

 13 individuals with undiagnosed psychoses some of whom were possibly 

 manic-depressive cases and we may confidently expect that there will be 

 additional cases among the siblings before they outgrow the age of incidence. 

 Taking these into consideration there is a fair degree of likelihood that the 

 total patients would reach 18 or even more, and this would indicate a sig- 

 nificant divergence from a chance result. Because of the much greater num- 

 ber of individuals represented in the families of the 95 female patients these 

 results must be given greater weight than those for the remaining families. 



As indicated earlier in this report, the analysis has not yet been completed 

 and our conclusions are therefore tentative. Bearing this in mind we may 

 say that our data do not indicate that families in which one member has a 

 manic-depressive psychosis are likely to develop relatively more psychotic 

 individuals than will be found in the undifferentiated population. But 

 there is some reason for believing that in such families a disproportionate 

 number of individuals with manic-depressive psychoses will appear. 



