Psychological well-being, or eudaimonia, features strongly in theories of human development and thriving. However, the factors of eudaimonia are debated, and their genetic architecture has not been studied in detail.

METHOD: A classical twin design was used to decompose behavioral variance into genetic and environmental components implemented in a multi-group, multivariate structural equation modeling framework. Subjects were 837 pairs of adult US twins from the nationally representative MIDUS II sample. Psychological well-being was measured using the 42-item Ryff Psychological Well-being Scale, which assesses autonomy, environmental mastery, personal growth, positive relations with others, purpose in life, and self-acceptance.

RESULTS: Substantial genetic influences were observed on all components of well-being. Attempts to model these 6-factors as reflecting a single common psychological mechanism gave a poor fit to the data. The best-fitting model supported the existence of five distinct genetic effects. Effects of shared-environment were weak and non-significant. Unique-environment effects for all measures were mostly trait specific.

CONCLUSIONS: These results indicate that psychological well-being is underpinned by a general genetic factor influencing self-control, and four underlying biological mechanisms enabling the psychological capabilities of purpose, agency, growth, and positive social relations.