Thesis advisor: James R. Mahalik / Objectives. Adolescent friendships play a particularly critical role in one’s physical, social, and emotional development. Difficult, inequitable, friendships in late adolescence and young adulthood are particularly concerning as the experience one has in these formative friendships can negatively impact one’s physical and psychological development (Ehrlich, Hoyt, Sumner, McDade, & Adam, 2015; Engels & Bogt, 2001; Hartup, 1996; Parker, Rubin, Erath, Wojslawowicz, & Buskirk, 2006). The goal of this dissertation was to examine one particular type of problematic and inequitable peer relationship experienced in late adolescence and young adulthood, colloquially termed a “high-maintenance” friendship. Specifically, this study examined the association between high-maintenance friendships and social emotional adjustment in late adolescents and young adults in a college setting and had four overarching purposes. First, it provided a preliminary definition for the construct of high-maintenance friendships among late adolescents and young adults in a college setting. Second, it explored late adolescents’ and young adults’ beliefs around why they have stayed in friendships that were high-maintenance. Third, the study applied the principles of interdependence theory to high-maintenance friendships and examined whether individual-level factors such as self-esteem, behavioral expectations, attachment style, loneliness, and gender were linked to the likelihood that one will stay in a high-maintenance friendship. Fourth, the study explored whether the degree to which a high-maintenance friendship impacted one’s emotional well-being (i.e., making them upset) was associated with one’s likelihood of staying in the high-maintenance friendship. Method. Participants were 256 late adolescents and young adults from a mid-size, elite, private university in the Northeastern United States (Mage = 19.09 years; 53.1% female). A mixed method, two-phase, exploratory, sequential design was implemented across two phases. The first phase implemented a qualitative content analysis in an effort to identify, develop, and define the construct high-maintenance friendships. The second phase of the study utilized a series of hierarchical linear regression analyses to explore the relationships between individual level characteristics and one’s likelihood of staying in high-maintenance friendships. Results. Qualitative analyses yielded a three-factor model, suggesting that late adolescents and young adults conceptualize the most salient characteristics of a high-maintenance friendship as: 1. one sidedness, 2. requiring substantial effort, and 3. general high expectations. Additionally, qualitative analyses generated a four-factor model of environmental obstacles that late adolescents and young adults recognized as why they stayed in a high-maintenance friendship: 1. positive friendship qualities, 2. shared experiences, 3. shared contexts, and 4. decrease in high-maintenance behavior over time. Quantitative analyses challenged the study’s hypotheses and indicated that lower levels of emotional closeness expectations and lower levels of avoidant attachment style predict to increased likelihood of staying in a cross-sex high-maintenance friendship. Quantitative analysis also indicated that the more a participant endorsed that the high-maintenance friendship impacted their emotional well-being, the less likely they were to stay in the friendship. Conclusions. The findings across the four phases of this study extend the current literature on difficult peer friendships in late adolescence and young adulthood by highlighting that: (a) high-maintenance friendships are inequitable, but those who experience social emotional distress in the friendship tend to not stay in the friendships, (b) there may be an optimal level of tolerable inequity which one can have in a close friendship without experiencing social emotional distress, and (c) there may be ways to increase one’s social emotional resilience and to restore an optimum level of inequity, even in problematic, high-maintenance friendships. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Lynch School of Education. / Discipline: Counseling, Developmental and Educational Psychology.