Opioid dependence is an increasing global health concern, particularly among pregnant women. The Methadone Maintenance Treatment (MMT) is considered a first-class standard treatment for pregnant opioid dependent women, as it can reduce foetal and birth complications, relapse, and social adversity. There is a limited number of studies examining the developmental outcomes of school-aged children born to mothers in MMT. Children born to methadone maintained mothers are identified as a dual hazard population, due to prenatal opioid exposure, social adversity and caregiver psychological factors. The degree to which of these factors contribute to language, externalising behaviours and internalising behaviours is unknown.

This thesis has three aims: i. To describe the extent and nature of language, externalising problems, and internalising problems of children born to mothers maintained on methadone at age 9.5 years. ii. To examine the associations between prenatal methadone exposure, social adversity, caregiver psychological factors and language outcomes at age 9.5 years. iii. To examine the associations between prenatal methadone exposure, social adversity, caregiver psychological factors and externalising and internalising problems at age 9.5 years.

This cross-sectional study draws on data from a prospective Methadone in Pregnancy longitudinal study. At the 9.5 year wave, 80 methadone exposed children and their caregivers, and 98 comparison children and their caregivers were assessed. The Clinical Evaluation of Language Fundamentals - Fourth Edition Semel et al. (2006), was used to measure children’s language. The teacher rating scale for the Behaviour Assessment System for Children, Second Edition (Reynolds & Kamphaus, 2004) was used to measure externalising and internalising problems. Factors related to social adversity and caregiver psychological factors were obtained during comprehensive caregiver interviews and used to predict child developmental outcomes at 9.5 years.

Study findings show at age 9.5 years methadone exposed children have poorer language and their teachers’ reports indicate higher rates of externalising problems relative to the comparison children. No differences were found in teachers’ ratings for internalising problems between methadone exposed children and the comparison children. A greater proportion of methadone exposed children displayed comorbid low language, externalising problems and internalising problems relative to the comparison group. Methadone group status did not predict low language at 9.5 years. Gender was the only factor that predicted low language at 9.5 years. Predictors of externalising problems included methadone group status, gender, and social adversity such as low SES, being from a minority group and being parented by a single caregiver. Methadone group status, social adversity and caregiver’s psychological factors failed to predict internalising problems.

Overall, findings from the present study indicate that methadone exposed children have low language and higher levels of externalising problems relative to the comparison children. Different predictor factors are associated with different developmental domains. Findings suggest multidisciplinary interventions are necessary to support this group of children and their families to guide positive developmental trajectories.