Familial and environmental aetiologic factors in paranoid psychosis quantified by a new statistical method

Abstract

A new mathematical model for quantification of familial factors was used in this study of psychiatric morbidity among the first-degree relatives of 25 patients with paranoid psychosis. The method provides a measure, a familial score of psychiatric morbidity of practical value in correlation analysis since it is applicable at different numbers of relatives per proband, excludes the influence of systematical errors, and allows the inclusion of background factors. A total of 159 first-degree relatives above the age of 15 were traced, 44 (28 %) of whom were found to have a history of psychiatric disorder. The familial score of psychiatric morbidity, which varied between 2.0 and 23.0 in the 25 patients, was not significantly correlated to neurophysiological findings or clinical picture. A highly significant negative correlation between the familial score and parental age suggested that the relative influence of nonfamilial factors on the development of psychiatric disorder may be increased with increasing parental age. R. Anelsson, Deportment of Psychiatry and Neurochemistry, University of Lund, Box 638, S-220 06 LundPathogenetic effects of both familial (e.g., genetic factors) and non-familial factors (e.g., environmentally induced brain damage, viral infection) have long been recognized in a wide range of psychiatric disorders (NIMGAONKAR et al. 1988;MENDLEWICS 1988). The relative influence of these factors have been difficult to evaluate, however, not least because no satisfactory method has been available. In the present study of psychiatric morbidity in the families of 25 patients with paranoid psychosis, the influence of familial and non-familial factors on the clinical characteristics of paranoid psychosis were evaluated by means of a new statistical method. The method made it possible to calculate a familial score of psychiatric morbidity, i.e., a measure of the relative influence of familial and environmental factors associated with psychiatric disorder. Since the method provides a numerical value directly applicable in correlation analysis, it facilitates the analysis of large samples and excludes the influence of systematical errors. Subjects and methods PatientsConsecutively admitted in patients with acute paranoid psychosis and born in Sweden were considered for participation in the study. The following diagnostic groups according to DSM I11 (American Psychiatric Association 1980) were found: atypical psychosis (n=9), acute paranoid disorder (n=7), paranoia (n=4), schizo-affective psychosis (n=2), organic delusional syndrome (n=2) and paranoid schizophrenia (n=l). Those with major affective disorders, dementia concomitant, physical disorders, and substance abuse disorders were excluded. Twenty-five patients, 9 men and 16 women, aged 25-76 years (mean age 57), were admitted in the study. Five of the patients had n o previous admission to psychiatric hospital, 3 had more than 10 previous admissions, and the median number of previous admissions was 4. The duration of psychosis varied between 0-40 years (mea...