The Etiology of Loneliness: Insights from Twin and Family, Genome-Wide, and Epigenetic Studies.

Loneliness is a growing public health concern, and several genetically informed research designs have been applied to studying its etiology. These approaches have revealed that loneliness has a highly polygenic architecture (a great many genetic variants each accounting for tiny percentages of between-person variability), a large impact of environmental factors, and links with gene regulatory processes. With this strong genetic component and high within-person stability, traditional loneliness scales behave surprisingly "trait-like", overlapping with personality constructs like neuroticism. We argue that greater use of idiographic designs and attention to construct contamination within nomothetic designs can improve inquiry into the etiology of loneliness as a dynamic and distinctive phenomenon. However, even with improved measurement, the biological pathways towards the development of complex behavioral traits are notoriously difficult to unravel. We highlight promising emerging methods and conclude with recommendations for studies that leverage multiple genetically informed paradigms (e.g., combining genomic and epigenomic approaches).