Owner of a lonely heart: The stability of loneliness across the life span.

Individuals feel lonely when they perceive a discrepancy between their aspired and their actually experienced amount of closeness and intimacy in social relationships. In the present study, we disentangled developmental constancy factors, time-varying factors such as person-environment transactions, and stochastic mechanisms as sources of interindividual differences in loneliness by applying STARTS models in nationally representative samples from Germany (n = 13,397), Switzerland (n = 6,599), Australia (n = 30,496), and The Netherlands (n = 12,810). Across the 4 studies, we found trait-like sources reflecting developmental constancy factors and the influence of time-varying factors to account for 19-43% and 23-30% of interindividual differences in loneliness, respectively. Depending on the type of measurement instrument, state-like stochastic mechanisms accounted for 30% to 55% of interindividual differences, whereby multi-item measures were less affected by stochastic mechanisms. We found gradual sex differences but considerable differences between age groups regarding the amount of interindividual differences in loneliness accounted for by the three sources. Taken together, the results demonstrate that interindividual differences in loneliness are to a large degree trait-like. Based on these findings, we discuss implications for theory and measurement. (PsycInfo Database Record (c) 2020 APA, all rights reserved).