Abstract
Attachment security (i.e., low levels of attachment anxiety and avoidance) is important for both partnered and long-term single people’s well-being. However, research gaps limit knowledge to what extent attachment processes generalize to single people. Research has often not distinguished global and relationship-specific attachment; most studies of single people were cross-sectional; and little is known about attachment change and its co-development with well-being. The present study examined selection into long-term singlehood, change in relationship-specific attachment, and co-development with life satisfaction. We used longitudinal data spanning 30 months (N = 3,542; 39,492 assessments; 82% women; M_age = 34.54) and compared consistently single, consistently partnered, and intermittently partnered people. Baseline global, romantic, and friend-specific avoidance, but not anxiety, prospectively predicted remaining single. Compared to consistently partnered people, consistently single people showed higher global and romantic attachment insecurity, and both groups decreased mostly in parallel. However, single people increased slightly more adaptively in some of the non-romantic attachment models. Intermittently partnered people were similar in romantic attachment at baseline to single people but became more secure over time. Across most attachment models, people who increased in attachment security also increased in life satisfaction. This co-development was similar between groups, except that decreasing romantic avoidance was less closely tied to increasing life satisfaction among single people. Together, persistent differences in global and romantic attachment may reflect selection into relationship status rather than distinct development. In addition, similar attachment–well-being links across groups indicate that attachment operates in similar ways in both partnered and long-term single people.