In this study of 1,408 adult participants, we found that people who experienced more childhood maltreatment had less social support in adulthood, and that social support was associated with a significantly lower risk of MDD. Total social support, subjective support and support utilization mediated the relationship between childhood maltreatment and adult MDD. We also found that the mediating effect of different types of social support was different in different sex. Only subjective social support mediated the relationship between childhood maltreatment and adult MDD in males, while both subjective support and support utilization mediated the relationship between childhood maltreatment and adult MDD in females.
We found that social support mediated the relationship between childhood maltreatment and adult MDD. This is consistent with previous research 18,40. There may be a biological mechanism in the mediating effect of social support on childhood maltreatment and MDD. Studies have found that both childhood maltreatment and MDD patients have increased amygdala activation, CRP, IL-6, and other inflammatory factors41–44, and not affected by lifestyle45. Higher levels of social support decreased amygdala activity and the levels of these inflammatory factors46. Therefore, abnormal amygdala function and inflammatory factor levels may partly explain the biological mechanism of the mediating effect of social support on childhood maltreatment and MDD. Another reason may be psychological factors. A study of 505 military recruits found that the recruits who had been abused as children tended to adopt more negative coping styles, such as avoidance and fantasy, withdraw in interpersonal relationships, interact less with peers, and reject others more, so they had lower subjective and objective social support and support utilization47,48, which may be related to the fact that people with childhood maltreatment often experience more depression.
Our study supports the role of subjective social support and support utilization in mediating models, but does not support the mediating effect of objective social support. Our study found that subjective support was the only one of the three types of support that was able to mediate the relationship between childhood maltreatment and MDD for both men and women, which highlighted the effect of subjective support. Previous studies have suggested that subjective social support is more correlated with MDD than objective social support and support utilization38,49, which was basically consistent with our findings. Previous studies found that subjective social support can maintain family stability and reduce anxiety and depression17, and poor family relationships are more likely to cause MDD13. Subjective social support characteristics mainly reflected in the closely related to the individual subjective feeling, and subjective social support this kind of perceptual reflects in many studies, and negatively correlated with depression 50,51, even the most strongly associated of any type of social support49. This may be because the perception of subjective social support, shaped by early family experiences, helps individuals gain more resources to cope with stress, according to a study 52. Another study analyzed that childhood maltreatment leads to abnormal development of neurotic and psychotic personality traits, thus reducing the perception of subjective social support and increasing the risk of depression53.
We only found sex differences in the mediating effect of support utilization on childhood maltreatment and MDD. In women, support utilization was an intermediary between childhood maltreatment and adult MDD, but not in men. One study pointed to a protective effect of support utilization on women's mental health54. Other studies found that after puberty, women have higher attachment needs and need more social activities to participate in with their peers. When interpersonal problems, poor utilization of social resources and decreased utilization of social support occur, they are more prone to have depressive symptoms than men55. A meta-analysis from China showed that women had a significantly greater negative association between social support and depression than men, and that women were more likely to get help from social support49. Scholars had also discussed and studied the causes of sex differences in social support, and summarized the sex differences in social support into psychodynamics, social role and evolution, and social construction56. However, in general, there are few studies on sex differences in support utilization in the childhood maltreatment-MDD mediation model, and more studies in this aspect are needed in the future.
We did not find the mediating effect of objective social support on childhood maltreatment and MDD. Few studies had shown that childhood maltreatment could affect objective social support in adulthood. One study found that objective social support has no significant effect on depression57. Another study showed that the protective advantage of objective support on mental health is mainly reflected in special groups, such as empty- nesters58. These findings may indicate that objective social support may have no mediating effect on childhood maltreatment and MDD.
The strengths of this study are as follows: First, this study analyzed the mediating effect of total and different types of social support on childhood maltreatment and MDD in detail. Second, we analyzed the mediating effect of social support in male and female, respectively, which provided basis for further personalized intervention. Third, as a multi-center study, the subjects were continually recruited from outpatient clinics of 9 research centers in China, which represented the MDD patients to some extent. Fourth, variables such as age, ethnicity, culture, work, and marital status that have a clear impact on target variables in existing studies were controlled to reduce confounding. The main limitations are as follows: First, the cross-sectional design of this study makes it difficult to evaluate the effect of social support on long-term outcomes of MDD. Second, social support and child maltreatment were assessed by participants themselves, which may be influenced by recall bias and depressive status. However, the researchers found that even in the serious maltreatment case, the risk of mental illness was lower in the absence of subjective reporting, while the risk of mental illness was higher in the subjective reporting of childhood abuse in adulthood43. Therefore, we conclude that recall bias of childhood maltreatment in our study may have a minor effect on the results.