An investigation has been carried out into the familial aspects of obsessional neurosis on 144 patients treated at Belmont and Netherne Hospitals. A study was made of the incidence among the first-degree relatives of the obsessional patients of mental illness for which psychiatric treatment had been sought. The scores of the Maudsley Personality Inventory of patients and their relatives were investigated. Forty-seven patients completed a M.P.I. form, and of these 33 agreed to their relatives being approached. Eighty-eight of the 96 first-degree relatives who were approached completed a form, and in addition 11 spouses completed a form.
(1) The incidence of psychiatric illness among first-degree relatives of obsessional neurotics was 9.3 per cent. (10.9 per cent. for relatives of patients who were interviewed personally).
(2) Classical obsessional neurosis among the relatives were found in only two cases. However, several were diagnosed as suffering from a phobic anxiety state, which some authors classify as an obsessional neurosis.
(3) A raised mean N score and a depressed mean E score were found in the obsessional patients.
(4) Contrary to expectation, mean N scores of first-degree relatives were below the mean normal score. The mean E score for parents was slightly depressed but for siblings this score was raised.
(5) These findings indicate that psychiatric illness occurs frequently among relatives of obsessional neurotics, but do not support the view that the obsessional personality or classical obsessional neurosis (obsessions accompanied by compulsions) are genetically determined.