| Depression is one of the most prevalent,disabling and costly mental health conditions in China and also worldwide.It is projected to be the leading cause of disease burden throughout the world by 2030.One promising avenue for preventing depression and informing its clinical treatment lies in uncovering the genetic and environmental determinants as well as their mutual functioning mechanisms.Adolescence is a critical time for studying vulnerability to depression as there is greater risk for depression onset during this period.However,during adolescence,particularly during the transition from early to mid-adolescence,research has shown individual trajectories or heterogeneity in the development of depression rather than a general increasing developmental pathway.Using longitudinal data from the Longitudinal Study of Chinese Children and Adolescents(LSCCA)project hold by Prof.Zhang,the present research is the first to investigate the roles of dopaminergic system genes,maternal parenting(ages lOand 11 years)and peer victimization(ages lOand 11 years)in the trajectories of depressive symptoms from early to mid-adolescence(ages 11 to 16 years)within a sample of 1090 Chinese adolescents(50%girls).The dopaminergic system genes examined in the present study include dopamine receptor D2(DRD2)TaqIA and A241G;catechol-O-methyltransferase(COMT)Val158Met and Ala72Ser and monoamine oxidase A(MA OA)T941G polymorphisms.With regard to the heterogeneous trajectories of depressive symptoms,we found that:(1)Within this Chinese sample(N=1090,50%female adolescents),three trajectories of depressive symptoms from early to mid-adolescence were identified:(i)low-stable(36.1%),(ii)moderate-increasing(44.5%),and(iii)high-increasing(19.4%).(2)The three-trajectories model found in the whole sample was confirmed in both male and female adolescents(male adolescents:N = 545,low-stable(35.6%),moderate-increasing(42.7%),and high-increasing(21.7%);female adolescens:N= 545,low-stable(41.1%),moderate-increasing(42.0%),and high-increasing(16.9%)).Moreover,there were no gender differences in the distributions of the three trajectories of depressive symptoms.(3)Adolescent self-perception at ages 10 and 12 differed significantly across the three trajectories of depressive symptoms in the whole sample,as well as in male and female adolescents.The results suggest good discriminant validity across the three trajectories of depressive symptoms in the present study.With regard to the roles of maternal parenting and peer victimization in the heterogeneous trajectories of depressive symptoms,we found that:(1)Maternal parenting and peer victimization independently but not interactively predicted trajectory membership of depressive symptoms.However,these two factors were also negatively correlated with each other,therefore,our results only partially supported the indepent effect between maternal parenting and peer victimzation.(2)Maternal parenting significantly predicted trajectory membership of depressive symptoms both directly and indirectly via peer victimization.The result suggests an indirect model between maternal parenting and the heterogeneous trajectories of depressive symptoms via the role of peer victimization.With regard to the interactive effects of dopaminergic system genes with maternal parenting and peer victimization on the heterogeneous trajectories of depressive symptoms,we found that:(1)A241G AA homozygotes were at increased odds to follow the high-increasing vs.low-stable trajectory.More importantly,the A241G polymorphism and maternal parenting also interacted in predictingtrajectories of depressive symptoms.Only for G-allele carriers,but not for AA homozygotes,high quality of maternal parenting decreased the odds to follow the high-increasing vs.moderate-increasing trajectory.Only for AA homozygotes,but not G-allele carriers,high quality of maternal parenting increased the odds to follow the low-stable vs.the moderate-increasing trajectory.(2)The DRD2TaqIA,COMTVal158Met and Ala72Ser,as well as MAOA T941G polymorphisms had neither a direct nor an interactive effect with maternal parenting on trajectory membership.(3)In male adolescents,the T941G T allele increased the chance to follow the moderate-increasing vs.low-stable trajectory.More importantly,the T941G polymorphism interacted with peer victimization in predicting trajectory membership.Compared with G-allele carriers,high peer victimization rendered T-allele carriers more likely to follow the high-increasing instead of moderate-increasing and low-stable trajectories.However,the T941G polymorphism had no direct or interactive effect with peer victimization on trajectory membership in female adolescents.(4)The DRD2 TaqIA and A241G,COMT Val 158Met and Ala72Ser polymorphisms had no interactive effects with peer victimization on trajectory membership of depressive symptoms.Finally,by the above stepwise analyses and further integrative model analysis,we found that in male adolescents,maternal sentivitiy significantly predicted trajectories of depressive symptoms through peer victimization.More importantly,the MAOA T941G polymorphism moderated such indirect effect.This is the first study to systematically investigate the roles of dopaminergic system genes,maternal parenting and peer victimization in trajectories of depressive symptoms in adolescents.The current findings highlight the importance of examining G×E interactions in longitudinal development of depressive symptoms over adolescence,and support a developmental versus static nature of G×E effects.Moreover,the presnt study provides the first evidence for an indirect effect,but not an independent or additive effect,between maternal parenting and peer victimization on trajectories of depressive symptoms.Although the underlying mechanisms still need to be further investigated,this exploratory study provides us important and useful information about the genetic and environmental underpinnings of depressive symptoms in adolescents.This study may have important implications for the prevention and intervention programs targeting at decreasing the risk for adolescent depressive symptoms,particularly given the potential modifiable nature of maternal parenting and its crucial role in GxE effects as well as in dominating peer victimization. |
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