Despite various efforts to prevent child maltreatment, child maltreatment incidents are increasing in number, creating a social resentment that goes beyond grief. The experience of abuse or neglect in childhood is a serious hazard to social and psychological development and adaptation throughout the entire growth process, from infancy to early adulthood.1 Childhood maltreatment causes a variety of internal and external problems, as well as unstable attachment and emotional control difficulties.2 Furthermore, childhood maltreatment has been a risk factor for adulthood mental disorders (such as depressive disorders or anxiety disorders), as well as more negative prognoses and poorer social adaptation.3 There are reports that parents who have experienced maltreatment in childhood have negative or abusive behavior toward their children, suggesting an intergenerational transmission of child maltreatment experiences.4 In short, childhood maltreatment is a major worldwide public health issue.

The characteristics of childhood maltreatment might differ from country to country based on their social and cultural background.5 In Korea, corporal punishment for children has been condoned in a cultural atmosphere that emphasizes a hierarchal social structure and parental authority.6 In a previous study, the pattern of child maltreatment in Korean families differed from that of non-Korean families in Los Angeles.7 Compared with all other groups, immigrant Korean families were 4 times more likely to be accused of physical abuse but were less likely to be accused of neglect.7 This previous study was conducted on Korean immigrants living in Los Angeles. There is a need to explore the prevalence of childhood maltreatment and its impact on mental health in the general population of Korea.

So far, there have been limited data on mental health of adults who had experienced childhood maltreatment. Some studies have evaluated the difference in symptoms with and without childhood maltreatment in specific disease groups (i.e., depression, psychosis) in clinical settings.89 Another study investigated the association of childhood maltreatment with mental health based on symptoms such as depressive mood rather than by diagnosis.10 In Korea, there have been no large-scale studies on the impact of childhood maltreatment on mental disease (diagnosis) in the general population. Although several large-scale general population studies have been conducted in other countries, additional studies are needed in Korea due to social and cultural differences. There is also a need to investigate and address mental illness outcomes based on the diagnosis rather than the symptoms, given that the prognosis and treatment strategies might vary depending on the diagnosis of maltreatment in individuals who exhibit the same symptoms.

We employed data from the 2016 Korean Epidemiologic Catchment Area study (KECA-2016) and analyzed the association of each type of childhood maltreatment with mental disorders and suicidality in adults. We also assessed whether there is a dose-response relationship: i.e., as the frequency of each childhood maltreatment increases, the odds ratios (ORs) of adverse mental health increases.

We explored the association of childhood maltreatment with adulthood mental health in the general community-residing population. Childhood maltreatment was associated with increased rates of mental disorders and suicidality in adulthood, regardless of the sociodemographic characteristics and mental disorders. In all areas of suicidality, we identified the association with each type of childhood maltreatment, and the association was stronger in the more serious form of suicidality (suicide attempts). Dose-response patterns for mental disorders and suicidality (particularly in suicide attempts) were observed in most types of maltreatment victims. Victims of frequent emotional neglect are particularly likely to have attempted suicide.

In previous studies, the prevalence of childhood maltreatment in the adult general population varied greatly from study to study. The prevalence of physical abuse ranged from 8.4% to 46.0%,1021 that of emotional neglect ranged from 7.1% to 9.4%,2223 that of psychological abuse ranged from 7.9% to 33.1%,2425 and that of sexual abuse ranged from 6.0% to 16.2%.2124 These differences might be due to a lack of consistent definitions as to what constitutes each type of childhood maltreatment, and the lack of consensus on the methodology to assess the maltreatment (e.g., rating scale).26 In addition, differences in study characteristics (e.g., adult participant's age distribution), data collection methods (e.g., face-to-face method, telephone surveys, self-completed questionnaire) might have affected these differences in prevalence.

In this study, the prevalence of abuse by type was comparable to that of previous studies; however, the prevalence of sexual abuse was much lower than that reported in previous studies.212324 Considering the report that Korean families were less likely to be charged with sexual abuse (1.8%) when compared to non-Korean families in Los Angeles (5.6%), this could be due to cultural influence.7 Difference in cultural values and beliefs across countries might be the underlying cause affecting the estimated prevalence of childhood sexual abuse.27 Child sexual abuse is known to be perpetrated mostly by family members and acquaintances.2829 In Korea, family harmony is considered important as a way to preserve the ideal family as an intact unit in the culture atmosphere emphasizing family cohesiveness and vertical social structure.630 Individuals might therefore be less likely to commit child sexual abuse so as to preserve family harmony and prevent the loss of family reputation.30 Meanwhile, we should consider that child sexual abuse might have been underreported. There is a report that experiences of abuse are less disclosed in a collectivist culture such as Korea than in individualistic cultures.2731 Within the collective tendency, an individual's identity is embedded in the group to which they belong (e.g., family, community, school), and the needs of the group take precedence over the needs of the individual.32 Thus, individual family members may be less likely to disclose the sexual abuse experiences in order to protect the family unity, harmony, and continuity above their own individual well-being.532

In this study, experience of childhood maltreatment was associated with most types of mental disorders. Previous studies reported that childhood maltreatment victims were associated with alcohol use disorders and nicotine use disorders,3334 which was observed in this study. These individuals might use alcohol and tobacco as a coping mechanism to alleviate negative mood and decrease anger and stress.3536

For mood disorders, all types of childhood maltreatment were associated with dysthymic disorder and major depressive disorder. Victims of childhood maltreatment might form a negative cognitive style for depressive disorder as they try to understand why the negative events occurred.37 Hypothalamic-pituitary-adrenal (HPA) axis hyperactivity and reduced inhibitory feedback are persistent consequences of childhood maltreatment.38 In addition, the risk of depression from childhood maltreatment is modified by changes in serotonin transporter and brain-derived neurotrophic factor genes.39

As in previous studies, childhood maltreatment was associated with anxiety disorders including PTSD, and GAD.25 Childhood maltreatment can be perceived as an intrusive and persistent threat, which increases the anxiety sensitivity of its victims.40 Emotional neglect hinders the formation and maintenance of secure attachment relationships, and, consequently, insecure attachment relationships make the victims more vulnerable to anxiety disorders.25 In particular, the ORs of PTSD were higher than the ORs of other mental disorders in the victims of childhood maltreatment. In terms of biological vulnerability, childhood maltreatment leads to dysregulation of the HPA axis, which might predispose to PTSD in adulthood.41 Childhood maltreatment can also cause cognitive biases about self, others, and the world, which could contribute to the onset of PTSD in adulthood.42

In accordance with previous studies, we found no statistical associations between each childhood maltreatment and OCD, panic disorder, social phobia, and specific phobia.4344 Previous studies have reported that the vulnerability to phobias (social phobia and specific phobia) is not directly affected by environmental factors and that it is more likely to be inborn (i.e., heritability: social phobia 65%, specific phobia 63%).4546 Pertaining to OCD and panic disorder, genetic factors play a major role in the occurrence of the disease (i.e., heritability: OCD 48%, panic disorder: 48%).4748 In this respect, certain anxiety disorders (phobias, OCD and panic disorder) are less likely to be affected by environmental factors such as childhood maltreatment. Although some previous studies have shown significant associations with these disorders, the possibility of a multiple comparisons problem was not considered in these studies.495051 Analysis of our data without applying any method to correct type I errors caused by a multiple comparisons problem revealed a statistical significance regarding OCD and social phobia; however, this significance disappeared following the Bonferroni correction.

Meanwhile, our analysis only considered cases of mental disorder with onset at 18 years or older, thereby assuming that childhood maltreatment had occurred before the onset of the mental disorder. As a result, in some disorders wherein the mean age of onset is usually mid-childhood to early adolescence (i.e., specific phobia and social phobia), the number of cases used in the analysis were considerably reduced.5253 Hence, results for various disorders with an early age of onset necessitate a more cautious interpretation. Nonetheless, it is very difficult to confirm the causality between childhood experience and disease occurrence in a cross-sectional study, and thus it is necessary to carry out a large-scale longitudinal study to overcome this limitation.

Victims of all types of childhood maltreatment were associated with suicidality in adulthood. Childhood maltreatment victims experience insecure attachment relationships, impaired emotional awareness and reward processes, and increased impulsiveness.54 In other words, victims suffer from their impairment in development processes associated with emotional regulation and interpersonal skills.55 These disruptions might also increase vulnerability to suicidal behavior when the victims face stressful events. In addition, the association of childhood maltreatment and suicidality might result from epigenetic modifications. Childhood maltreatment alters the HPA stress responses through the epigenetic hyper-methylation of the Nr3C1 gene, which increases the risk of suicide.56 As such, the experience of childhood maltreatment is a significant risk factor for suicidality.

A dose-response relationship has been established for the impact of the number of experienced traumas on adverse mental health.57 Similar to previous studies, this study found that frequent victims of most of the types of maltreatment were more likely to have mental disorders and suicidality than occasional victims. These findings emphasize the importance of implementing early detection and intervention as an approach to preventing adverse mental health.

In particular, the strongest association with suicidality was found for emotional neglect. Parental rejection and low parental warmth and responsiveness, which are characteristic of emotional neglect, lead to low self-esteem, hopelessness, and a negative view of the world.2533 Thus, although emotional neglect might be difficult to discern compared with physical and sexual abuse with the more obvious signs, the importance of evaluating emotional neglect should be emphasized.

As well as emotional neglect, sexual abuse was also strongly associated with suicide attempts after controlling for sociodemographic factors and mental disorders. Sexual abuse in childhood has an impact on stress-induced neurobiological structure changes and susceptibility to environmental influences.55 Dysregulation of the HPA axis is strongly associated with sexual abuse.55

This study has some limitations, the first of which is its cross-sectional design, preventing us from making causal interpretations. To clarify the temporal relationship between child maltreatment and mental disorders, the cases in this study were limited to an onset of disease at the age of 18 years or older. A longitudinal study is needed to confirm a more accurate causal relationship. Second, all childhood maltreatment data were collected retrospectively and only from respondents, which entails the possibility of information bias (i.e., recall bias, reporting bias). Given that the respondents were asked to report on childhood maltreatment that occurred decades ago, there might be recall bias, especially among the older participants. Negative views, stigma, and discrimination against victims are common when it comes to sexual abuse, which can lead to reporting bias. Accordingly, longitudinal studies using information collected through various sources such as neighbors, teachers, and polices, are needed. Nevertheless, our study has the following strengths. Our study was the first to investigate the association of childhood maltreatment with mental disorders and suicidality in the general adult population of Korea. Moreover, we employed a validated structured interview tool (K-CIDI) for the assessments of mental disorders.

In conclusion, this study indicates that childhood maltreatment is associated with mental disorders and suicidality in adulthood. The dose-response patterns show the need for early detection and early intervention of childhood maltreatment. From a public health perspective, policy makers should devise methods to reduce the incidence of childhood maltreatment and clinicians should detect and intervene in the early mental health problems of childhood maltreatment victims.