Objective: The present study investigates whether either adolescents' psychological distress and/or perceived parenting predicted the occurrence of NSSI. Furthermore, the consequences of NSSI are examined in a three-wave longitudinal study. Design: The sample at time 1 (age 12) consisted of 1396 adolescent reports and 1438 parent reports. At time 2 (age 13), 827 adolescent reports and 936 parent reports were obtained. Time 3 (age 14) included 754 adolescent reports and 790 parent reports.Psychological distress of adolescents was measured using the Strengths and Difficulties Questionnaire.Perceived parenting behaviors were examined by the Parental Behavior Scale and the Psychological Control Scale. Results: A total of 10% of the adolescents engaged in NSSI at least once before age 15.Higher psychological distress of adolescents at time 1 was associated with the presence of NSSI at time 2 or 3. The association between psychological distress at time 1 and perception of decreased parental rule setting at time 3 was mediated by the presence of NSSI at time 2. Conclusions: The present study showed that psychological distress at age 12 predicts NSSI over time and that parental awareness of NSSI changes the perception of parenting behaviors. Keywords:Non-suicidal self-injury, adolescence, psychological distress, parenting, longitudinal. According to the dominant theories (e.g., Nock, 2009), NSSI is related to both (1) adolescent (intrapersonal) and (2) caregivers (interpersonal) factors which shape and maintain NSSI. Several intrapersonal correlates (most importantly emotion regulation and psychological distress) are hypothesized to be interwoven with interpersonal correlates (e.g., parenting, attachment, peer influences). With regard to caregivers characteristics, parenting behaviors may play an important role in both onset of NSSI (e.g., modulating physiological arousal/regulation, invalidating emotions, stressful life events such as abuse) and in maintaining NSSI (e.g., controlling behavior of parents). Although both intrapersonal and interpersonal correlates are hypothesized as exerting influences on onset of and maintaining NSSI, until now no longitudinal studies have examined these hypotheses. Furthermore, current dominant theoretical model (e.g., Nock) lack insight into consequences of NSSI over time. This large-scale, three-wave longitudinal study examined (1) the interaction between intrapersonal and interpersonal vulnerability factors for the NSSI, and (2) the consequences of NSSI over time. The present study focuses on the interplay between psychological distress as a potential intrapersonal correlate of NSSI (i.e., levels of internalizing and externalizing Running title: Longitudinal study of NSSI

This study investigated (1) reciprocal links among parental psychological control, peer rejection, and adolescent externalizing (aggressive and rule-breaking behaviour), and (2) the moderating effect of an adolescent genetic factor (biologically informed polygenic score for dopamine signalling). Three-year longitudinal data from 1,116 adolescents (51% boys; M age = 13.79) and their parents included psychological measures (adolescent-reported psychological control, peer-reported rejection, and parent-reported aggressive and rule-breaking behaviour). Cross-lagged analyses showed bidirectional effects between psychological control and both aggressive and rule-breaking behaviour and a unidirectional effect of peer rejection on both forms of problem behaviour over time. Multigroup structural equation modelling revealed genetic moderation only for rule-breaking behaviour: for adolescents with intermediate levels of dopamine signalling significant environmental effects were present, whereas adolescent effects of rule-breaking behaviour on psychological control were significant for adolescents with both intermediate and high profiles and effects on peer rejection only for adolescents with high dopamine profiles. Statement of contribution What is already known on this subject? Parental psychological control is related to adolescent externalizing problems. Experiencing peer rejection reinforces aggressive and rule-breaking behaviour. Single-gene studies show that dopaminergic genes influence externalizing problems directly or in interaction with the environment. What does this study add? Parental psychological control and adolescent aggressive and rule-breaking behaviour exacerbate one another longitudinally. Longitudinal associations between peer rejection and both subtypes of externalizing behaviour are unidirectional. With a polygenic approach, dopaminergic moderation is present for rule-breaking behaviour only.

Investigating the interplay between parenting dimensions and styles, and the association with adolescent outcomesResearch has indicated that a strictly dimensional or parental style approach does not capture the full complexity of parenting. To better understand this complexity, the current study combined these two approaches by using a novel statistical technique, i.e. subspace K-means clustering. Four objectives were addressed. First, the study tried to identify meaningful groups of parents in longitudinal adolescent reports on parenting behaviour. Second, the dimensional structure of every cluster was inspected to uncover differences in parenting between and within clusters. Third, the parenting styles were compared on several adolescent characteristics. Fourth, to examine the impact of change in parenting style over time, we looked at the cluster membership over time. Longitudinal questionnaire data were collected at three annual waves, with 1,116 adolescents (mean age = 13.79 years) at Wave 1. Based on five parenting dimensions (support and proactive, punitive, psychological and harsh control), subspace K-means clustering, analysed per wave separately, identified two clusters (authoritative and authoritarian parenting) in which parenting dimensions were interrelated differently. Authoritative parenting seemed to be beneficial for adolescent development (less externalising problem behaviour and higher self-concept). Longitudinal data revealed several parenting group trajectories which showed differential relations with adolescent outcomes. Change in membership from the authoritative cluster to the authoritarian cluster was associated with a decrease in self-concept and an increase in externalising problem behaviour, whereas changes from the authoritarian cluster to the authoritative cluster was associated with an increase in self-concept and a decrease in externalising problem behaviour.

Theory and research both point at epigenetic processes affecting both parenting behavior and child functioning. However, little is known about the convergence of mother and child’s epigenetic patterns in families. Therefore, the current study investigated epigenetic covariance in mother–child dyads’ methylation levels regarding four stress-regulation related genes (5HTT, NR3C1, FKBP5, and BDNF). Covariance was tested in a general population sample, consisting of early adolescents (Mage = 11.63, SDage = 2.3) and mothers (N = 160 dyads). Results showed that mother and offspring 5HTT and NR3C1 methylation patterns correlated. Furthermore, when averaged across genes, methylation levels strongly correlated. These findings partially supported that child and parent methylation levels covary. It might be important to consider this covariance to understand maladaptive parent–child relationships.

Findings highlight the role of behavioral problems as a risk factor for NSSI in early adolescence, a rarely studied developmental period during which NSSI often first starts. Findings suggest that one possible pathway for the attachment-NSSI association among young adolescents is through behavioral problems. Therapies that improve child-parent attachment may reduce NSSI among young adolescents both directly, and indirectly by improving behavioral problems.