4.1 Adolescents with schizoid reported higher scores for adverse life events and childhood trauma
The study determined that boy and girl adolescents with schizoid had suffered more emotional abuse and adverse life events, and displayed greater aggressive behavior, compared with boy and girl adolescents without these features. In addition, schizoid girl adolescents were more likely than those without schizoid features to have experienced physical abuse and emotional neglect. The results of the present study are consistent with other reports in which individuals with schizoid personalities were more likely to experience adverse life events and childhood trauma compared with healthy control groups. In addition, Kelleher et al. found that patients with psychotic disorders were more likely to have experienced more severe childhood maltreatment compared with healthy individuals. A meta-analysis showed that childhood maltreatment was quite common among people with a high risk of psychosis, and childhood trauma was strongly associated with psychotic status.
These results imply that adolescents with schizoid features are likely to live in an environment where maltreatment is pervasive. In addition, people with schizotypal personality disorder displayed an abnormal subjective experience of emotion, such as lack of social pleasure, which makes them more difficult to understand in social settings. The results of the present study also indicated that childhood trauma affects boy and girl schizoid adolescents differently. Girl schizoid adolescents are affected more broadly. And this is the first study to report differences in between the genders in adolescents with schizoid.
4.2 Schizoid was a predictor of aggressive behaviors
In the present study, adolescents with schizoid achieved higher aggression scores compared with normal peers, and linear regression analysis suggested that schizoid could predict aggressive behavior in boy and girl adolescents. This is consistent with most other similar studies, in which aggression was common in people with mental disorders[12, 14, 43]. Wong et al. found that schizotypal personality disorder in children and adolescents was associated with reactive aggression. This may be due mainly to the close link between aggressive behaviors and symptoms, and symptoms may affect social associations. For example, patients with mental disorder may display aggressive behavior under the influence of command auditory hallucination[45, 46]. Individuals with schizoid are likely to feel insecure when under the influence of delusion, which leads to hostility and aggressive behavior. In addition, many people with schizoid personality and schizophrenia have interpersonal problems. They are more likely to misunderstand the intentions of others while communicating, which can result in aggressive behavior. Some studies report that people with schizophrenic personality and schizophrenia are more likely to display violent behavior due to substance abuse. Raine et al. found that in adolescents schizoid elicit peer victimization, which also results in aggressive behavior. Therefore, interventions such as social skills training and peer education are recommended for adolescents with schizoid to prevent aggressive behaviors.
4.3 Adverse life events and type of maltreatment type predict aggressive behaviors differently by gender
In the present study, the linear regression analysis revealed that adverse life events could positively predict aggressive behavior in adolescent boys and girls. Those who experienced adverse life events were more likely to display aggression. These results are consistent with previous articles[50, 51]. A study conducted among adolescents in Ontario Canada found that adolescents exhibited aggressive behavior because of neglect, specifically when their caregivers no longer played a caregiving role.
In the present study, emotional neglect was a positive predictor of aggressive behavior in boy adolescents, and emotional abuse was a positive predictor of aggressive behavior in girl adolescents. This suggests a difference in gender response to trauma that affects aggressive behavior. A prior study found that childhood neglect influences adult violent behavior. Another research reported that chronic neglect at an early age predicted aggressive behavior in later life, and compared with girls, boys were more likely to show aggressive behavior. McGuigan et al. found that neglect was a powerful predictor of aggressive behavior among male adolescents, after controlling for domestic violence and physical abuse. This is consistent with our results.
In our study, emotional abuse was a positive predictor of aggressive behavior in girl adolescents, not in males. Given the small effect of emotional abuse on aggressive behavior, a sampling error may be the cause. Interestingly, sexual abuse was negative predictor of aggressive behavior in girl adolescents, which is inconsistent with another study. Kozak et al. found that boy and girl adolescents who had experienced sexual abuse were 1.7-fold more likely to behave violently compared with those who had not. Their results showed that sexual abuse predicted violent behavior more in boys than in girls. This does not agree with our results, in which sexual abuse was a negative predictive factor for aggression in girls but not in boys. The one possible reason may be that girls were more distressed and were more prone to self-blame after sexual abuse and were more likely to use coping strategies of withdrawal and attempted amnesia. In addition, girls who suffered from sexual abuse were more likely than boys to develop internalized problems such as suicide attempts and depression.
The effect of adverse life events and childhood maltreatment on aggressive behavior may involve a variety of psychological and biological mechanisms. For example, abused subjects experienced higher levels of narcissistic vulnerability, which partially mediated the association between childhood maltreatment and aggression. A potential biological mechanism may be related to genetically based phenotype. It has been reported that aggression is a complex behavior involving a synergetic interaction between genetics and environment. Other studies found that childhood maltreatment may modify the association between social information processing and adult aggression, leading to increased aggressive behavior.
4.4 Mediation model of schizoid and aggressive behavior
In accord with previous studies, the present found a close association between schizoid, childhood maltreatment, adverse life events, and aggressive behavior[43, 61]. These results are consistent with our second and third hypotheses, that childhood trauma may mediate the link between schizoid and aggression, and that adverse life events may be as important as childhood trauma in influencing the association between schizoid traits and aggression. The model showed that adverse life events mediated the association between schizotypal personality disorder and aggressive behaviors.
Adolescents with schizoid features are more likely to experience adverse life events, which in turn is a documented risk factor of aggression. In the boys of the present study, emotional neglect mediated the association between schizoid and aggressive behaviors, while in the girls, emotional and sexual abuse mediated this association. It is worth mentioning that in girls sexual abuse has a negative mediating effect on the association between schizoid and aggressive behaviors. Our results are in agreement with Norton-Baker et al.'s, which found that links between sexual abuse and aggressive behavior tended to be stronger in girls than in boys.
Among adverse life events, reducing childhood maltreatment in adolescents with schizoid traits may be crucial to reduce their aggressive or violent behavior, whereas parental love, the friendly support of teachers and classmates, and financial resources may be important protective factors. For example, Family Attachment Narrative Therapy was used to heal the bad effect of childhood maltreatment. If adolescents with schizoid traits are raised in an abusive environment, then timely interventions, such as behavior management and therapy, should be implemented at home and at school.
4.5 Moderation model of schizoid and aggressive behavior
The interaction between childhood trauma and adverse life events affected aggressive behavior in the girls, but not in boys. This is the first time that this gender difference is reported. Functional magnetic resonance imaging (fMRI) studies have shown that in girls maltreatment could lead to changes in the amygdala. These changes can result in abnormal activation when adolescents with childhood maltreatment experience adverse life events, leading to aggressive behaviors. In addition, another study found that childhood maltreatment can be associated with dysfunction of the hypothalamus-pituitary-adrenal axis (HPA), and aggressive behavior is closely related to HPA function. Our findings suggest that girls are highly affected by adverse life events and develop aggressive behavior after experiencing childhood maltreatment. This may be because girls are more prone to attenuation of the HPA axis after experiencing childhood maltreatment.