Depression is an increasingly important area in psychology and education. Investigating depressive symptoms is a continuing concern for adolescents. Recently, an increased interest extends to emerging adulthood. According to the viewpoint of ecological system theory, previous studies in process-person-context-time model have highlighted the important factors such as ideal self, parent-child relationship, teacher-student relationship. This study aimed to investigate the trajectories of depressive symptoms from adolescence to emerging adulthood by considering three predictors — self-esteem, parent-child, and teacher-student relationships. Using AMOS 23.0, two factor latent growth curve model with random intercepts and random slopes was used to analyze the longitudinal data. In this panel study, a sample of 992 students were selected from the Taiwan Youth Project (TYP) in three waves from 2002 to 2009 (at Grade 9, Grade 12, and the senior year of undergraduate). The average scores in each of the three waves served as indicators of latent intercepts and slopes for each of the four study variables. By using hierarchical cluster analysis with dendrogram, we were able to divide all subjects into two groups as low and high depressive symptom groups respectively. Four research questions with correspondent eleven research hypotheses were investigated. That is, H1a: The intercept of self-esteem has negative influence on the correspondent slope of self-esteem. H1b: The intercept of parent-child relationship has negative influence on the correspondent slope of parent-child relationship. H1c: The intercept of teacher-student relationships has negative influence on the correspondent slope of teacher-student relationships. H2a: The intercept of self-esteem has negative influence on the intercept of depressive symptoms. H2b: The intercept of self-esteem has negative influence on the slope of depressive symptoms. H2c: The slope of self-esteem has negative influence on the slope of depressive symptoms. H3a: The intercept of parent-child relationship has negative influence on the intercept of depressive symptoms. H3b: The slope of parent-child relationship has negative influence on the slope of depressive symptoms. H4a: The intercept of teacher-student relationships has negative influence on the intercept of depressive symptoms. H4b: The intercept of teacher-student relationships has negative influence on the slope of depressive symptoms. H4c: The slope of teacher-student relationships has negative influence on the slope of depressive symptoms.
The main findings of this study are shown as follows: (1) The intercepts of self-esteem, parent-child, and teacher-student relationships all negatively affected their respective slopes. In addition, the intercepts of the high depressive group on these three variables were lower, and the slopes were greater, than those of low depressive group. (2) Among the three predictors, self-esteem was the most important one. The intercept of self- esteem affected the intercept of depressive symptoms; the slope in self-esteem also affected the slope in depressive symptoms in both groups. Surprisingly, in the high depressive symptom group, people with high self-esteem in Grade 9 had a higher positive depressive symptom slope in the future. (3) The intercept of parent-child relationship negatively affected the intercept of depressive symptoms for the low depressive symptom group, while the slope in parent-child relationship affected the slope in depressive symptoms for the high depressive group. (4) The intercept of the teacher-student relationship negatively affected the intercept of depression symptoms only in the low depressive symptom group. Based on these results, suggestions for practical applications and future research are also discussed. In brief, it is necessary to pay attention to students’ development of long-term self-esteem and other psychological and social factors even if an individual has good self-esteem from the beginning. It is worth noting that individuals with high self-esteem are likely to have greater changes in depressive symptoms in the future. If an individual has high self-esteem but cannot tolerate setbacks and failures, the slope in depressive symptoms will increase. Moreover, even if individuals have unfavorable family experiences in the early stages, they still have the possibility of improving parent-child relationships, showing that the parent-child relationship is not limited to a single point in time. Finally, the teacher-student relationship in early adolescence not only shows its long-term influence, but also becomes an individual’s protective factor for depression, helping individual to have better adaptability in future.