The Heritability of Attachment Systems

Attachment theory has strong environmental origins, from which it has been the broad consensus that variation in attachment is caused by variation in environments (shared and non-shared), with little role of genetic variation, especially in infants. However, the state of the behavior genetic evidence needs critical evaluation to discern whether such environmentalist claims are warranted. Here, I demonstrate that the majority of the available twin studies are not adequately powered to detect additive genetic effects if present, and that the majority of twin studies in infants are not adequately powered to detect shared environmental effects. Within the published research, I can find only three adequately powered twin studies on attachment: one in infants, one in adolescents, and one in adults. I conclude by presenting five observations from behavior genetic studies that future developmental frameworks of attachment must account for.

Establishing a Twin Register: An Invaluable Resource for (Behavior) Genetic, Epidemiological, Biomarker, and ‘Omics’ Studies

Twin registers are wonderful research resources for research applications in medical and behavioral genetics, epidemiology, psychology, molecular genetics, and other areas of research. New registers continue to be launched all over the world as researchers from different disciplines recognize the potential to boost and widen their research agenda. In this article, we discuss multiple aspects that need to be taken into account when initiating a register, from its preliminary sketch to its actual development. This encompasses aspects related to the strategic planning and key elements of research designs, promotion and management of a twin register, including recruitment and retaining of twins and family members of twins, phenotyping, database organization, and collaborations between registers. We also present information on questions unique to twin registers and twin-biobanks, such as the assessment of zygosity by SNP arrays, the design of (biomarker) studies involving related participants, and the analyses of clustered data. Altogether, we provide a number of basic guidelines and recommendations for reflection when planning a twin register.