This study examined the effect of close friendship intensity as a potential amplifier of an adolescent's preexisting tendencies toward depressive and aggressive symptoms. A diverse community sample of 170 adolescents and their closest friends was assessed via multiple methods, and adolescents were followed from age 16 to 17. Results supported the hypothesized effect, with more intense close friendships interacting with higher baseline levels of behavioral symptoms to predict greater relative increases in symptoms over time. Effects were observed for both depressive and aggressive symptoms, and appeared with respect to multiple observational measures of friendship intensity. Findings are interpreted as suggesting that seemingly disparate phenomena (e.g., co‐rumination for depression and deviancy‐training for aggression) may both be dependent upon the intensity of the adolescent's social connections.

Adolescent association with deviant and delinquent friends was examined for its roots in coercive parent–teen interactions and its links to functional difficulties extending beyond delinquent behavior and into adulthood. A community sample of 184 adolescents was followed from age 13 to age 27, with collateral data obtained from close friends, classmates, and parents. Even after accounting for adolescent levels of delinquent and deviant behavior, association with deviant friends was predicted by coercive parent–teen interactions and then linked to declining functioning with peers during adolescence and greater internalizing and externalizing symptoms and poorer overall adjustment in adulthood. Results are interpreted as suggesting that association with deviant friends may disrupt a core developmental task—establishing positive relationships with peers—with implications that extend well beyond deviancy-training effects.

Adolescents’ negative expectations of their peers were examined as predictors of their future selection of hostile partners, in a community sample of 184 adolescents followed from ages 13 to 24. Utilizing observational data, close friend- and self-reports, adolescents with more negative expectations at age 13 were found to be more likely to form relationships with observably hostile romantic partners and friends with hostile attitudes by age 18 even after accounting for baseline levels of friend hostile attitudes at age 13 and adolescents’ own hostile behavior and attitudes. Furthermore, the presence of friends with hostile attitudes at age 18 in turn predicted higher levels of adult friend hostile attitudes at age 24. Results suggest the presence of a considerable degree of continuity from negative expectations to hostile partnerships from adolescence well into adulthood.

This study assessed the key aspects of romantic relationship dissolution in emerging adulthood as predictors of future mental health and romantic qualities. It utilized a longitudinal, multiinformant, multimethod study of 160 participants with their romantic partners and close friends followed from ages 20–25, with a breakup assessed at age 22. Having control over initiating a breakup at age 22 predicted relative increases in peer-rated internalizing symptoms and autonomy-undermining interactions with a new partner at ages 23–25. Having a greater understanding of the reasons for a breakup predicted lower self-reported internalizing symptoms and relative decreases in partner-reported romantic conflict as well as relative increases in selfreported relationship satisfaction and peer-rated intimate relationship competence at ages 23–25. Predictions remained after accounting for numerous potential confounds including age 20–22 baseline relationship quality, social competence, internalizing symptoms, and gender. Implications for understanding links between breakup characteristics on emerging adult psychological and relationship functioning are discussed.

Adolescent romantic relationships have the potential to affect psychological functioning well into adulthood. This study assessed adolescent romantic relationship qualities as long-term predictors of psychological functioning utilizing a longitudinal multi-method, multi-informant study of 80 participants (59% female; 54% Caucasian, 35% African American, 11% mixed or other race) assessed at age 17 along with their romantic partners and at ages 25–27. Controlling for gender, family income, and baseline mental health, partner-reported hostile conflict at age 17 predicted relative increases in internalizing behaviors from age 17 to 27. In contrast, observed teen support with their partner during a help-seeking task at age 17 predicted relative decreases in externalizing behaviors over time. The results are interpreted as suggesting qualities that may help determine whether adolescent romances have positive vs. negative long-term psychological health implications.

Struggles managing conflict and hostility in adolescent social relationships were examined as long-term predictors of immune-mediated inflammation in adulthood that has been linked to long-term health outcomes. Circulating levels of interleukin-6 (IL-6), a marker of immune system dysfunction when chronically elevated, were assessed at age 28 in a community sample of 127 individuals followed via multiple methods and reporters from ages 13 to 28. Adult serum IL-6 levels were predicted across periods as long as 15 years by adolescents’ inability to defuse peer aggression and poor peer-rated conflict resolution skills, and by independently observed romantic partner hostility in late adolescence. Adult relationship difficulties also predicted higher IL-6 levels but did not mediate predictions from adolescent-era conflict struggles. Predictions were also not mediated by adult trait hostility or aggressive behavior, suggesting the unique role of struggles with conflict and hostility from others during adolescence. The implications for understanding the import of adolescent peer relationships for life span physical health outcomes are considered.

Interview, self-report, peer-report, and observational data were used to examine parent and peer relationship qualities as predictors of relative changes in attachment security in a community sample of adolescents followed from age 14 to 24. Early maternal supportive behavior predicted relative increases in attachment security from adolescence to adulthood, whereas psychological control and interparental hostile conflict predicted relative decreases. Peer predictors of relative increases in security included collaborative and autonomous behaviors and lack of hostile interactions, with peer predictions growing stronger for relationships assessed at later ages. Overall, models accounted for sufficient variance as to suggest that attachment security across this period is well explained by a combination of stability plus theoretically predicted change linked to social relationship qualities.

Middle adolescents’ close friendship strength and the degree to which their broader peer group expressed a preference to affiliate with them were examined as predictors of relative change in depressive symptoms, self-worth, and social anxiety symptoms from ages 15 to 25 using multimethod, longitudinal data from 169 adolescents. Close friendship strength in midadolescence predicted relative increases in self-worth and decreases in anxiety and depressive symptoms by early adulthood. Affiliation preference by the broader peer group, in contrast, predicted higher social anxiety by early adulthood. Results are interpreted as suggesting that adolescents who prioritize forming close friendships are better situated to manage key social developmental tasks going forward than adolescents who prioritize attaining preference with many others in their peer milieu.

Negativity in parent–child relationships during adolescence has been viewed as a risk factor for teens’ future personal and interpersonal adjustment. This study examined support from romantic partners and close friends during late adolescence as protective against maternal negativity experienced during early adolescence. A combination of observational, self-report, and peer-report measures were obtained from a community sample of 97 youth (58 % female), their mothers, closest friends, and romantic partners assessed at ages 13, 18, and 20. Moderating effects suggested a protective effect of romantic support against maternal negativity across a variety of psychosocial outcomes, including depressive symptoms, self-worth, social withdrawal, and externalizing behavior. Protective effects were found even after controlling for initial levels of outcome behavior and observed support from close friends throughout adolescence. Receiving support from a romantic partner may provide teens with new, positive ways of coping with adversity and help them avoid more serious distress that may be predicted from maternal negativity when such support is not available.

The potential importance of depending on others during adolescence in order to establish independence in young adulthood was examined across adolescence to emerging adulthood. Participants included 184 teens (46% male; 42% non-White), their mothers, best friends, and romantic partners, assessed at ages 13–14, 18, 21–22, and 25. Path analyses showed that associations were both partner and age specific: markers of independence were predicted by participants’ efforts to seek support from mothers at age 13, best friends at 18, and romantic partners at 21. Importantly, analyses controlled for support seeking from these partners at other ages, as well as for other potentially confounding variables including attachment security, scholastic/job competence, and physical attractiveness over time. Moreover, analyses suggested the transfer of support seeking behavior from mothers to best friends to romantic partners over time based on support given by the previous partner at an earlier age.