Description: This dissertation, "Early Modifiable Risk Factors for Childhood and Adolescent Mental Health" by Cherry, Leung, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Childhood and adolescent mental health is a major public health concern. Childhood behavioral problems and low self-esteem can predispose children to future depression. Mental health issues often emerge in adolescence making examination of potential early modifiable risk factors for these three mental health indicators crucial. Potential risk factors for mental health issues often reflect findings from Western settings where confounding by low socioeconomic position may occur, making it difficult to establish causation. Evidence from a setting with a different confounding structure, such as Hong Kong, is valuable in elucidating whether previous findings are contextually specific or biologically based. This thesis utilized a large (n=8,327) population-representative Chinese birth cohort, Hong Kong's "Children of 1997," from a developed non-Western setting with a different confounding structure, to 1) examine how behavioral problems and self-esteem may identify children with a predisposition to depressive symptoms and 2) examine the associations of early modifiable risk factors, including migration status, secondhand smoke (SHS) exposure, mode of delivery and type of child care (informal care such as in-home employed help or grandparent care), with these three mental health indicators: behavioral problems, self-esteem and depressive symptoms. This research study utilized parent-reported Rutter scores for behavioral and emotional problems at 7 and 11 years, self-reported Culture-Free Self-Esteem Inventories scores at 11 years and the Patient Health Questionnaire-9 (PHQ-9) depressive symptom score at 13 years to assess childhood and adolescent mental health. First, partitional clustering was used to generate homogeneous trajectories between 7 and 11 years for child behavior and changes in low self-esteem between 10 and 12 years; multivariable linear regression was then used to estimate their adjusted associations with subsequent PHQ-9 score. Second, multivariable linear regression was used to examine the adjusted associations of parental migration status, SHS exposure, mode of delivery and type of child care with the three mental health outcomes. This researcher found that in a graded manner, Rutter score trajectories (stable low, declining and rising) and self-esteem changes (stable high, rising and declining) were associated with more depressive symptoms. Parental migration was associated with better behavior at 7 and 11 years, but prenatal SHS exposure was associated with more behavioral problems. Mode of delivery was not associated with the three mental health outcomes. Meanwhile, in-home employed help was only associated with lower self-esteem and more depressive symptoms, although care by grandparents was associated with fewer behavioral problems. To conclude, in this population-representative Hong Kong birth cohort, sustained behavioral problems and low self-esteem were strongly associated with depressive symptoms, potentially highlighting the need for earlier identification of and intervention for mental health issues. Furthermore, parents and household members are targets for intervention since SHS exposure was found to be positively associated with child behavioral problems and in-home employed help was associated with low self-esteem and more depressive symptoms. Migrant parents and care by grandparents were associated with fewer behavioral problems, thus the