Association Between Sexual Behaviour and Depression in South Korean Adolescents: A Cross-sectional Study

Hyunkyu Kim Department of Preventive Medicine, Yonsei University College of Medicine, Seoul Wonjeong Jeong Department of Public Health, Graduate School, Yonsei University, Seoul Sung-In Jang Department of Preventive Medicine, Yonsei University College of Medicine, Seoul Eun-Cheol Park Department of Preventive Medicine, Yonsei University College of Medicine, Seoul Youseok Kim (  kysmd@yuhs.ac ) Department of Hospital Administration, Graduate School of Public Health, Yonsei University, Seoul


Background
Globally, depression and suicidal behaviour in adolescents are becoming a major social problem with huge economic repercussions [1]. In the United States, 13.3% of adolescents reported more than one symptom of major depressive episodes, and the prevalence of depression in older adolescents stood at 25% [2,3]. A cross-national study in the United States reported high rates of suicidal ideation in youths, ranging from 24% to 29.8%, with between 3.1% and 8.8% having made suicide attempts [4]. As demonstrated by these statistics, suicide is a serious concern, one that is now the second leading cause of death in the United States [5,6].
The situation in the Republic of Korea is similar. In a 2016 survey, 19.7% of male students and 27.8% of female students reported that they had experienced depression [7]. The 2018 cause of death statistics by the South Korean government showed that suicide was the rst cause of death in teenagers, with a prevalence of 5.8 in 100,000 [8].
Thus, the appropriate management of depression and suicide is an important public health concern. Adolescence is a period of physical, mental, and emotional growth when values and personality are malleable to change; therefore, the identi cation and management of factors affecting the occurrence of depression in this population is of the utmost signi cance.
As previously mentioned, adolescence is a critical period for not only physical growth but also psychosexual development, including sexual identity and orientation. Thus, sexual behaviours during this period can have signi cant mental and social impacts. In the past, studies have examined the physical and psychological effects of adolescent sexual behaviour. In this context, Vasilenko et al. suggested a conceptual framework for the effects of sexual behaviour on mental, physical, and social health [9]. They posited that sex could be a more negative experience for early adolescents than older teenagers. Another study on 7th to 12th graders in the United States reported that sexual behaviour increased the odds ratios (ORs) of depression and suicidality, and that this effect was compounded when combined with drug abuse [10]. These studies, though limited in scope and sample sizes, suggest that sexual behaviour in adolescents can result in depression.
Sexual behaviour can have a greater impact on adolescents than other age groups, and the intensity can vary depending on the cultural and social climate. South Korea is relatively conservative with regard to sex; sexual activity among youths is viewed particularly negatively, as demonstrated by a survey comparing the sexual behaviours and consciousness of South Korean and Dutch adolescents [11]. The concept of chastity is important to South Koreans, and there is a general trend toward the suppression of sexual desires. However, considering the rise in sexual activity among adolescents, as demonstrated by the decrease in the average age for the initiation of sexual activity in middle and high school students from 14.3 years in 2011 to 13.3 years in 2014, the impact of adolescent sexual behaviour on psychiatric symptoms such as depression is increasing [12]. Thus, it is necessary to conduct a detailed and large-scale examination of the relationship between sexual behaviour and depression in adolescents.
The aim of this study was to investigate the association between sexual behaviour and depression in a large sample of South Korean adolescents, after adjusting for covariates associated with depression prevalence.
Furthermore, we aimed to identify differences in the severity of depression based on the presence or absence of sexual behaviour.

Study population and data
The data analysed in this study were obtained from the 2017-2019 Korea Youth Risk Behavior Web-based Survey (KYRBS), conducted by the Ministry of Education, Ministry of Health and Welfare, and Centers for Disease Control and Prevention. The purpose of this survey, which targets middle and high school students, is to evaluate the health status and health behaviour of South Korean adolescents in order to provide basic data for the formulation of health policies. The anonymous survey is conducted annually with about 400 high schools and 400 middle schools. Survey items are variable to change slightly every year, and weight values are suggested for combined analysis for several years.

Design
The study employed a cross-sectional design.

Depression
Participants were asked whether they had experienced depressive feelings that interfered with daily life for more than two weeks in the previous year. As the KYRBS did not directly measure depression severity, we divided participants into depression severity groups based on suicidality: a) those with mild depression, who had not experienced any suicidal ideation, planning, or attempts, and b) those with severe depression, who had experienced suicidal ideation, planning, or attempts within the previous 12 months.

Sexual behaviour
Sexual behaviour was assessed through questions such as whether the participants had ever engaged in sexual intercourse and whether they had received sex education through any means in the previous 12 months.
Participants who indicated that they had experience of sexual intercourse were asked about contraceptive methods.

Covariates
Age, socioeconomic status, academic grades, and family structure were included in the sociodemographic covariates. Socioeconomic status was categorised as high, middle, or low, and based on family structure, we classi ed participants as either having one or both parents or none. The analysis was also adjusted for healthrelated covariates including smoking status, alcohol use, perceived stress level, and self-reported health status.

Statistical analysis
Chi-square tests were used to analyse and compare the variables. To examine the relationship between sexual behaviour and depression, we conducted a multivariate logistic regression analysis after adjusting for covariates. Subgroup analyses were performed to investigate the combined associations of sexual behaviour and other covariates with depression. Subjects with depression were divided into two groups, and the difference in the relationship of sexual intercourse with the two severity groups was analysed. The results are presented as ORs and 95% con dence intervals (CI) to compare the prevalence of depression. The analyses were performed with strati ed sampling variables (strata) and weighted variables suggested by the KYRBS. All analyses were carried out using SAS software version 9.4 (SAS Institute, Cary, North Carolina, USA), and p-values < 0.05 were considered statistically signi cant.

Results
The general characteristics of the study population strati ed by gender are presented in Table 1. A total of 178,664 participants including 91,309 males and 87,355 females were included in the analysis. Among them, 20.7% of males and 31.3% of females reported having experienced depression in the previous year. Participants who had sexual intercourse experience reported higher rates of depression regardless of gender. Older students reported higher rates of depression than their younger counterparts. Low socioeconomic status was associated with a higher prevalence of depression than middle and high socioeconomic status. Higher perceived stress was associated with a greater prevalence of depression. Family structure, school grade, alcohol status, smoking status, physical activity, and self-reported health status were additionally identi ed as being statistically signi cantly associated with depression. Experience of sex education was not statistically correlated with depression. Table 2 shows the results of the multivariate logistic regression analysis between depression and sexual intercourse experience. After adjusting for covariates, the prevalence of depression was higher in participants of both genders with sexual intercourse experience (adjusted OR: 1.71, 95% CI: 1.59-1.83 in males, adjusted OR: 1.47, CI: 1.33-1.61 in females). After adjusting for covariates, higher age was associated with lower depression.
Regardless of gender, the absence of both parents was statistically associated with depressive experience. Other covariates including socioeconomic status, school grade, alcohol/smoking status, physical activity, perceived stress level, self-reported health status, and sex education experience were also correlated with depression, as shown in Table 3.
Subgroup analyses were conducted to assess the combined associations of sexual intercourse experience and other sociodemographic variables with depression, as shown in Table 3. Sexual experience was correlated with a high prevalence of depression in every subgroup except sex education. Participants with sexual intercourse experience showed higher ORs for depression whether they attended sex education. However, this was not statistically signi cant in females without sex education experience (OR: 1.16, CI: 0.95-1.43).
The results of multivariate logistic regression analyses, conducted after dividing participants into the mild and severe depression groups, are presented in Table 4 and Figure 1. Regardless of gender, participants with sexual intercourse experience showed higher ORs for severe depression with suicidality than milder depression.

Discussion
In this investigation of a sample of South Korean adolescents, we identi ed that depression was associated with experience of sexual intercourse. Furthermore, we found that sexual intercourse experience had a stronger association with severe depression with suicidality than with milder depression without suicidal ideation, planning, and attempts. These results did not differ by gender and remained consistent after adjusting for covariates and subgrouping by sociodemographic variables. Depression in youths has different characteristics comparing to adults, including conduct behaviours. It is widely known that risky behaviours, including sexual activity and drug abuse, are consequences of depression. In fact, Kessler et al. hypothesised that such behaviours act as self-medication in adolescents with depression [13].
Conversely, studies suggest that these behaviours have biological and psychological effects that increase the risk of depression [14]. According to Hallfors et al., it is more reasonable to conclude that depression occurs later and as a consequence of sex and drug abuse because depression itself did not increase the risk of sex and drug abuse; instead, those with more risky behaviours had a stronger association with depression [15]. In our study, while we could not deduce causality in the relationship between sexual intercourse and depression in adolescents, it is reasonable to conclude that depression occurred after sexual intercourse because the survey asked about depression only within the past year while there was no such limitation on their reports of sexual intercourse.
As the KYRBS did not use an instrument to measure depression severity, we divided the participants into two groups based on suicidality: milder depression without suicidality and severe depression with suicidal ideation, planning, and attempts. The higher ORs of severe depression indicate a possible positive correlation, in that greater sexual behaviour could increase the severity of depression. Thus, the appropriate management of adolescents with sexual experience is important to prevent them from experiencing severe depression. Previous studies have suggested the need for abstinence programmes for students; these include delaying sexual intercourse in early adolescents on the grounds that it is associated with depression [16]. Conversely, some researchers are of the opinion that just abstinence is not effective, and that there is a need for more comprehensive research to plan proper sexual education that prevents depression in adolescents [17]. In the present study's subgroup analysis, there was no difference in depression prevalence between participants in early and late adolescence, which also supports the idea that just delaying sexual experience is not the solution. Also, in subgroup analysis with sex education, the prevalence of depression was higher in the group that had received sex education than the group that had not. Thus, conventional sex education in South Korea might not be successful at preventing depression associated with sexual intercourse. Simply delaying sexual intercourse or portraying it as something negative cannot prevent depression but even induce the symptom. Therefore, there is a need for appropriate sex education that can alleviate the risk of depression in adolescents.
This study has several limitations. First, the use of cross-sectional data prevents causal inferences regarding the relationship between sexual intercourse and depression prevalence in adolescents. Second, as the data were collected through a self-reported web-based survey, the possibility of recall bias or the participants having misunderstood some questions cannot be eliminated. Especially, the answers about socioeconomic status might lack accuracy because of the participants' lack of understanding of their parents' economic condition. Conversely, the results are based on subjectively reported economic status, which can more accurately re ect depressive feelings than objectively reported data. Third, as the survey targeted youths, questionnaire was kept deliberately simple and did not include a scale for assessing depressive symptoms.

Conclusions
In conclusion, this study identi ed the relationship between sexual behaviour and the prevalence of depression; adolescents with experience of sexual intercourse were more likely to have severe depression with suicidality. There is a need for further research using prospective designs to identify cause and effect in this relationship. Further, the formulation of appropriate sex education policies based on a comprehensive understanding of the relationship between the variables is necessary to alleviate the effect of sexual intercourse on depression in adolescents.

Consent for publication
Not applicable

Availability of data and materials
The data analysed in this study were obtained from the 2017-2019 KYRBS, which is available to the public. All data can be downloaded from the KYRBS o cial website (https://www.kdca.go.kr/yhs/home.jsp).

Competing interests
The authors declare that they have no competing interests.

Funding
No funding was received for this manuscript.
Authors' contributions YSK conceived, designed, and directed the study. HK and WJ conducted the statistical analysis. HK interpreted the data and wrote the rst draft of the manuscript. ECP and SIJ were in charge of revising the manuscript. All authors participated su ciently in the work and take public responsibility for appropriate portions of the content. Variables are presented as numbers and percentages.    Figure 1