Genetic probes of three theories of maternal adjustment: II. Genetic and environmental influences

This is the first report of the Twin Mom Study, an investigation. of three hypotheses concerning influences on maternal adjustment. These hypotheses c oncern the role of the marital and parent-child relationships in mediating genetic influences on maternal adjustment and on the importance of the moth ers' marital partners as a specifiable source of influences on their adjust ment not shared with their sisters. The study's sample of 150 monozygotic ( MZ) twins and 176 dizygotic (DZ) twins was drawn randomly from the Swedish Twin Registry and is, with some small exceptions, likely to be representati ve of women in the Swedish population. The sample included the marital part ners of these twins and their adolescent children. Self-report and coded vi deotapes were a source of information about family process. Results reporte d in this first report focus on comparability of American and Swedish sampl es on scales measuring psychiatric symptoms, and on an analysis of genetic and environmental influences on nine measures of mothers' adjustment. Resul ts suggest comparability between the US and Sweden. Genetic influences were found for all measures of adjustment, particularly in the psychological ma nifestations of anxiety and for smoking. The pattern of findings also under scored the importance of influences unique to each sibling within the twin pair, thus focusing attention on the potential role of marital partners in maternal adjustment. Results also suggested that experiences shared by the twin sisters, experiences unrelated to their genetic similarity, may influe nce their fearfulness and alcohol consumption. Our model did not include th ese influences and thus must be amended.