Background: Children born extremely preterm (EPT; <28 weeks gestation) and very preterm (VPT; <32 weeks gestation) are at an increased risk for a range of neurodevelopmental impairments compared to their full-term (FT) born peers. One important aspect of child development is social competence which significantly impacts long-term outcomes such as educational underachievement, internalizing problems, and difficulties with intimate relationships. This area of child development has not been well-studied with the preterm population. Preliminary research suggests that EPT/VPT born children experience more social competence difficulties than their term born peers, however, these existing studies are methodologically limited and have lacked a comprehensive examination of the nature of children’s friendships and peer experiences, their social behaviours and their social skills. Furthermore, few studies have been concerned with preadolescence, a critical period of development for peer relationships. Finally, no studies have examined the trajectory of social development in EPT/VPT born children across childhood and few have examined predictors of and/or associated risk factors of poor social competence. The tri-component model of social competence was adopted as a research framework. This model suggests that three components constitute social competence: social adjustment (broad social outcomes such as developing friendships and getting along with peers), social performance (nature and adequacy of one’s social interactions with others) and social skills (such as cooperation and relating to others).

Aims: Three studies were undertaken in this thesis to: 1) Describe the between-group differences in the social adjustment of preadolescent children born EPT and VPT relative to their FT peers at age 12 years and to identify family social background and 12-year concurrent child characteristics associated with poorer social adjustment; 2) Examine the between-group differences of the EPT, VPT and FT born children on the two lower components of the tri-component model, social skills and social performance at age 12 years and to examine the role of these components and child and family characteristics in explaining the between-group differences seen for the 12-year social adjustment outcomes; 3) Examine longitudinally the development of peer problems in children born EPT and VPT in comparison to FT born children at age 4, 6, 9 and 12 years and identify risk factors at age 4 years that may predict poor peer relationships at age 12 years. Method: A regional cohort of 44 EPT, 60 VPT, and 109 FT born children participated in a comprehensive neurodevelopmental assessment at age 12 years as part of a prospective longitudinal study. Detailed information was gathered from child, parent, and teacher about the children’s friendships, the extent of peer problems and victimization, their prosocial behaviour, aggressive behaviour, and their social skills using custom-written or standardized questionnaires. At ages 2, 4, 6, and 9 years, children were screened for socio-emotional and behavioural adjustment problems including peer problems using the parent and teacher rated Strengths and Difficulties Questionnaire. At age 2 and 4 years, parenting styles, maternal mental health and a range of child outcomes were also assessed using custom-written or standardized questionnaires/assessments.

Results: Within the social adjustment component, parents reported EPT but not VPT born children to have fewer friends and less contact with friends than FT born children (p ≤ .02). Child self-report showed a similar pattern although these between-groups differences did not reach statistical significance. However, 16% of EPT relative to 1−2% of VPT and FT born children reported being unsatisfied with their quantity of friends (p = .001). Based on parent and teacher reports, 32−37% of EPT compared with 3−8% of VPT and 8−9% of FT born children had peer problems (p ≤ .005). EPT and VPT born children had higher odds of experiencing frequent peer-victimization than FT born children (12−14% vs. 4%, p = .03 and p = .05, respectively). Peer relationship difficulties at age 12 years were associated with lower math fluency scores and higher inattention/hyperactivity and emotional scores. Frequent victimization was associated with younger maternal age, higher body mass index, less pubertal development, poor vision, and higher inattention/hyperactivity scores.

Results for the social performance component, showed that EPT born children had poorer prosocial behaviour compared to FT born children according to teacher report only (p = .01, Cohen’s d = 0.5). There were no significant differences found for aggressive behaviour between the three groups. EPT born children were reported by their parents to spend less time with friends than time FT born children spent with their friends (p = .02). In terms of social skills, EPT born children were at increased risk of interpersonal skill difficulties than FT born children (p = .001, Cohen’s d = 0.7). All social skills (interpersonal skills, parent and friend attachment, anxious rejection sensitivity) and two social performance variables (being a bully, and never spending time with friends) were associated with the social adjustment outcome of having peer relationship problems at age 12 years. With the inclusion of the 12-year associated characteristics (math fluency, emotional difficulties and hyperactivity/inattention reported earlier) only low levels of attachment to parents and friends, being a bully, and never spending time with friends remained statistically significant in the final model.

Interpersonal skills and angry rejection sensitivity were significantly associated with experiencing frequent victimization at age 12 years, however they did not remain so after the inclusion of the 12-year associated characteristics (hyperactivity and physical outcome variables described above) suggesting that victimization of these children is primarily a result of physical and behavioural factors suggesting further risk factors need to be highlighted. Finally, using longitudinal data, parent report showed statistically significant between-group differences in levels of peer problems at age 4, 6, 9 and 12 years of age (all p’s < .02). Teacher report showed statistically significant between-group differences in levels of peer problems at age 9 and 12 years of age (both p’s < .003). Furthermore, results suggest that EPT born children show that these high levels of peer problems are stable or possible worsening over time. Children with low cognitive ability, and high levels of hyperactivity/inattentive behaviour at age 4 years were at the highest risk of peer relationship problems at age 12 years.

Conclusions: EPT born children are at increased risk of a range of social difficulties within all components of tri-component model. These differences include increased levels of friendship and peer problems, and frequent peer victimization. VPT born children are at increased risk of frequent peer victimization. These problems emerge early and do not dissipate by preadolescent years. This research identifies a number of 4-year and 12-year child and family background variables that were associated with poor social adjustment outcomes in pre-adolescence. Routine assessment of the social development of EPT/VPT born children should be instigated in order to identify these at-risk children and intervene as early as possible. Multi-systemic interventions are discussed in relation to individual, family, and school based avenues of addressing the social difficulties and victimization these children experience. Addressing these social difficulties prior to high-school entry may reduce the broad and far-reaching impact that poor social competence can have on these children’s future development.