“Don’t invite them.” Ostracism of best and close friends in adulthood: Identifying the roles of peer-bullying behaviors and partner sexual interest.

Objective: The current research explored actor-initiated ostracism of best and close friends in adulthood with a focus on the role of group factors.Method: An international sample (N = 827; 75% Australian) of fluent English-speaking adults aged 18-84 years was used (73.4% female).Participants reported on a current best or close friendship.Results: Reported bullying behaviors (within friends and peer group) and sexual interest (within friends and romantic partners) were relatively common at low frequencies (approximately 20%) but uncommon at high frequencies.The ability of two types of group factors to explain actor-initiated ostracism of best and close friends was examined.The peer-bullying factors model explained 50% of variance in actor-initiated ostracism of their best or close friend, and the romantic partner sexual interest model explained 23%.The significance and effect sizes of all models and unique contributors remained unchanged when controlling for age, sexual orientation, gender, gender combination of friends, personality, and locus of control.Conclusions: The research highlighted the importance of assessing within friends and group factors when working with adults on friendship challenges and incorporating these themes in the development of adult friendship-based intervention programs. Highlights and Implications• One in five adults reported sometimes ostracizing or verbally victimizing their current best or close friend, but high frequencies of these behaviors were rare.• A peer-group bullying model explained 50% of the variance in actorinitiated ostracism of adult best and close friends.• A romantic partner sexual interest model explained 23% of actor-initiated ostracism of best and close friends in adult couple friendships.• The research challenges societal assumptions that best and close adult friendships are "immune" from group influences.Thus, the assessment of group factors in adult friendship therapy, and the inclusion of group-factor modules in adult friendship-based intervention programs, may be beneficial.