What differentiates suicidal ideation from depressive symptoms amongst Korean Young Adults aged 20-39 years?

Purpose: This study aimed to examine and compare factors in�uencing depressive symptoms from those in�uencing suicidal ideation in Korean adults aged 20–39 years. Methods: Data were collected from September 15 to 23, 2021 using an online survey company because of the limitations of face-to-face surveys during the coronavirus 2019 pandemic. Participants were also recruited from the Seoul Suicide Prevention Center. Suicidal ideation, depressive symptoms, and general health and demographic characteristics were determined based on existing standardized questionnaires. Multiple logistic regression analysis was used to determine associations with depressive symptoms and suicidal ideation. Results: Based on data from 1014 participants, age, sex, alcohol consumption, sleep duration, and stress were associated with depressive symptoms. In contrast, income, subjective health status, and stress were found to in�uence suicidal ideation; the effect of income disappeared when adjusted for depression. Lower income, poor subjective health status, higher stress levels, and depression were associated with a higher risk of suicidal ideation. Conclusions: These �ndings suggest that depression and suicidal ideation have distinct in�uencing factors and that simply viewing depression as a risk factor for suicidal ideation may lead to other important factors being overlooked. This study emphasizes the need for targeted interventions and prevention strategies to address speci�c factors associated with each outcome. Overall, this study provides valuable evidence for developing effective mental-health interventions and policies for young adults. Further research is recommended to delve deeper into the similarities and differences between depression and suicidal behaviors in this population.


Introduction
Recent statistics suggest a mental health crisis in young South Koreans, with higher suicide rates compared to the general population, and rapidly rising rates among those in their 20s.According to the World Health Organization's 2022 Mortality database, Korea's suicide rate among people in their 30s was 27.1 in 2020, the highest among the Organization for Economic Co-operation and Development (OECD) countries; the suicide rate among people in their 20s was 21.7, far exceeding the OECD average of 10.6 [1].Furthermore, 30.1% of Koreans treated for depression were young adults in their 20s and 30s in 2020 [2,3].
Although suicide is the leading cause of death among individuals aged 20-39 years in most countries, it is worth noting that the suicide rate among those in their 20s and 30s in Korea has been increasing since 2017, whereas that in the total population has been gradually decreasing since 2011 [4].The total suicide mortality rate has decreased from 26.9 to 26.0 over the past three years, whereas the suicide rate among those in their 20s has increased from 19.2 to 23.4 and from 26.7 to 27.3 among those in their 30s [4].
In South Korea, although there has long been concern about the high suicide rate among the older population, unfortunately, the younger generation has not been the focus of mental health research until recently.Studies on suicide have been conducted mainly on older adults and adolescents, and few have focused on young adults [5].Even in the existing studies, most included university undergraduate students [6][7][8].In the government-led Korean Basic Plan for Suicide Prevention established every ve years since 2004, policies on young adults have been omitted for the past 20 years, and only services for undergraduate students were included.Establishing measures at the national level for young people in their 20s and 30s was the Fifth Basic Plan in April 2023 [9,10].The lack of interest in mental health among young adults thus far has led to a lack of evidence to explain the mental health crisis, which is currently a signi cant social problem.As a result, policies for mental health protection and promotion among young adults are lacking, especially when compared to older adults, adolescents, and children.
Early adulthood is vulnerable to mental health related issues.During this period, the developmental burden of psychological and economical independence from parents begins.Whether intentionally or unintentionally, young adults experience relative deprivation and a fear of developmental tasks [11].They also experience stress and depression due to economic recession and unemployment [12].Considering the negative effect of personal economic hardship or low employment status on mental health [13,14], for young Koreans, among whom the proportion of non-regular workers is 30%, the risk of depression and other mental health disorders is likely to be increased [15].Depression has long been considered a signi cant contributor to suicidal ideation [16].However, it should not be regarded as the sole risk factor or antecedent of suicidal ideation; the relationship is complex and multifaceted, and depression and suicidal thoughts share some overlapping dimensions [17].It is important to note that not all individuals with depressive symptoms exhibit suicidal thoughts or behaviors [18].In an analysis of successful suicides in young adults, 55.4% of cases did not involve psychiatric diagnoses [1].Suicide attempters attribute interpersonal issues as signi cant triggers of psychiatric symptoms [19].Furthermore, according to research categorizing suicide types based on psychological autopsies of suicide victims, the most prevalent type among individuals younger than 30 years was acute stress resulting from interpersonal or economic factors, without any speci c vulnerability [20].Therefore, it is crucial to not overlook the possibility that the strong association between depression and suicidal behavior may be a result of overlapping characteristics rather than the former being a direct risk factor.In this context, it would be meaningful to determine factors in uencing depression and suicidal ideation and to compare them.
Various associations have been reported for factors in uencing depressive symptoms and suicidal ideation in previous studies.The known factors associated with suicidal ideation include socioeconomic factors, such as sex, marital status, education level, and income [21][22][23].Suicidal thoughts are more common in women [24], and higher socioeconomic status related to education and income is associated with a decreased likelihood of engaging in suicidal behaviors [23,25,26].An unmarried status has also been identi ed as a risk factor for suicidal ideation [22,27].Additionally, health characteristics, such as self-rated health and stress levels [21,28,29], and health behaviors, including sleep duration, alcohol consumption, and smoking, have been found to in uence suicidal ideation [30][31][32].Previous research has identi ed being female, low education level, low income, poor health status, high perceived stress, smoking, and being unmarried as factors related to depression [33][34][35].
Although depressive symptoms and suicidal ideation in young adults are not expressed by the same mechanism, studies comparing the related factors of these two outcomes in a single dataset through a wide range of social determinants are sparse.It is necessary to identify the factors in uencing depression and suicidal thoughts among young people at this stage and establish evidence for mental health policies.Effective policies to prevent depression, suicidal ideation, and suicide can only be proposed when accurate evidence is provided through a detailed analysis of the current status and characteristics of mental health in young people.Thus, this study aimed to identify and compare factors in uencing depression and suicidal thoughts among young Korean adults.This analysis of the mental health crisis of young Koreans is expected to explain how these two important mental health outcomes of indicated different things to the young generation.

Participants
The study population included young Koreans aged 20-39 years.The age range used to de ne the young generation in research varies.The lower limit is 15-20 years and the upper limit is 25-39 years [21,36,37].The generation classi cation is based on age, as well as on a cohort that shares the same experience.The new term "MZ generation," wherein the birth year ranges from 1981 to the 2000s, has recently emerged in Korea.They constitute a younger generation with unique characteristics that distinguish them from older generations [38,39].Based on these previous ndings, we limited the de nition of young adults to ages 20s-30s with similar characteristics as the MZ generation.
Participants based on the above de nition who voluntarily agreed to the purpose and contents of this study were included.Data from participants with unreliable or incomplete responses and missing variables were excluded from the analysis.

Data collection
We collected data using an online survey company due to the limitations of face-to-face surveys during the COVID-19 pandemic and sensitive information such as suicidal ideation.We conducted region-, age-, and sex-speci c Quota random sampling from the survey pool.Participants were also recruited from the Seoul Suicide Prevention Center.Data were collected from September 15 to 23, 2021.
Before beginning the survey, we explained the purpose and content of the study to the participants, their right to withdraw, and the option to revoke consent.We conducted a survey after obtaining informed consent regarding personal information from individuals who voluntarily wished to participate.For the bene t of vulnerable participants in mental health, we included the contact information of institutions of mental health assistance.The researchers received de-identi ed data from the survey company for analysis and compensation was provided to participants who completed the survey through the survey company.

Questionnaires
The survey items were developed through a literature review, expert consultations and in-depth interviews with counselors of suicide prevention centers.
Suicidal ideation was assessed by asking respondents binary questions about the presence of suicidal thoughts during the previous year.Depressive symptoms were measured using the Centre for Epidemiological Studies Depression Scale (CES-D-10) [40].The CES-D-10 consists of 10 items that assess the thoughts and feelings experienced during the previous week.Participants responded on a 4point Likert scale (0-3 points) ranging from "rarely (less than 1 day)" to "the most (5-7 days)."Items 5 and 8 were reverse-coded, and the total scores ranged from 0 to 30.Higher scores indicated greater levels of depressive symptoms; the cut-off score for depression is 10.This was converted into a binary variable using the CESD-10 scale cut-off score for analysis, to identify and compare factors related to suicide ideation and depression.The Cronbach's α value in this study was .879,whereas it was .7 in the previous study [41].Socioeconomic characteristics included age, marital status, educational level, and average monthly income.In the case of marital status, since no women responded that they were divorced/widowed, they were divided and analyzed based on their spousal status in the logistic regression model.Educational level was categorized as "college graduate or higher" and "high school graduate or lower" based on the highest level of education achieved.The monthly average income was investigated for all types of income, including unearned income, and divided into quartiles for analysis.
The health characteristics included subjective health status, sleep duration, stress, alcohol consumption, smoking, and regular exercise.Subjective health status was assessed using a 5-point Likert scale ranging from "very good" to "very poor."This was converted into a binary variable for analysis.Sleep duration was categorized based on previous research as "insu cient sleep (< 5 h)", "adequate sleep (6-8 hours)", and "excessive sleep (≥ 9 h)" [30].Stress was measured using a daily life stress measurement tool utilized in the Seoul Mental Health Perception Survey and Women's Family Panel.It consists of eight items and respondents are asked to rate their responses on a 4-point Likert scale ranging from "strongly agree" to "strongly disagree".Item 6 was reverse coded, and the score range was 8-32, with higher scores indicating higher levels of stress.In previous research, Cronbach's α value was .675[42], whereas, in this study, it was .685.Alcohol consumption and smoking were assessed by asking the participants about their current habits.Exercise level was investigated by asking whether the respondents engaged in physical activity for at least 30 min, three times a week.

Data analysis
The analysis was conducted using SPSS 25.0.for Windows (SPSS Inc., Chicago, IL, USA).Descriptive analysis was used for general characteristics and the prevalence of depressive symptoms and suicidal ideation.To identify factors associated with depressive symptoms and suicidal ideation among young adults, multiple logistic regression analysis was performed.Additionally, we analyzed the suicidal thoughts model by including depression as an independent variable to identify social determinants associated with suicidal thoughts while adjusting for depression.A two-tailed test was used, and p-values less than 0.05 were considered statistically signi cant.

Results
Responses were obtained from 1019 young adults.After excluding data from 5 respondents due to missing or incomplete data, a total of 1,014 young adults were included.
Among the study participants (Table 1), the average age was 30.3 ± 5.16 years (range 20-39), 48.4% were female, 49.7% were in their 20s, and 74.5% of participants were unmarried.Of these, 26.1% had a high school education or lower; 51.5% reported alcohol consumption; 24.8% were smokers, and 49.7% exercised regularly.The proportion of participants with adequate sleep was 82.6%, whereas 12.9% experienced insu cient sleep and 4.4% reported excessive sleep.The average stress score was 19.9 ± 4.00, and 17.8% of the participants perceived their subjective health as poor.The average monthly income was 344.5 million KRW.Among the participants, 42.1% reported having suicidal thoughts in the previous year, and 50.9% had a CES-D10 cutoff score above the threshold.2).With increasing age, the risk of depressive symptoms decreased (OR = 0.955; 95% CI = 0.920-0.991).Men had a higher risk of depressive symptoms than women (OR = 0.589, 95% CI = 0.417-0.832).Individuals who currently consumed alcohol had a lower risk of depressive symptoms than those who abstained from alcohol (OR = 0.676, 95% CI = 0.480-0.950).Those who experienced insu cient sleep had a 1.986 times higher risk of depressive symptoms than those with adequate sleep, whereas those with excessive sleep did not show a statistically signi cant difference.With increasing stress scores, the risk of depression increased (OR = 1.561; 95% CI = 1.470-1.657).In model 1, young individuals in the lowest income percentile were 1.587 times more likely to experience suicidal ideation than those in the highest income percentile (Table 3).Individuals who perceived their subjective health as poor reported a 1.502-times greater risk of suicidal ideation than those who perceived their subjective health as moderate or good.With increasing stress scores, the risk of suicidal ideation increased (OR = 1.171, 95% CI = 1.127-1.217).After adjusting for depression, the previously observed statistical signi cance related to income level ceased to exist.
In model 2 that adjusted depression, individuals experiencing depression were 2.16 times more likely to have suicidal ideation than those who did not.Individuals reported a 1.5-times higher risk of suicidal ideation when their subjective health was poor than those who perceived their subjective health as moderate or good.Furthermore, individuals who experienced a higher stress level also experienced an increase in suicidal ideation (OR = 1.108, 95% CI = 1.060-1.159).

Discussion
According to this cross-sectional representative survey of young Koreans whose suicide rate has jumped signi cantly in recent years, we con rmed that factors in uencing suicidal ideation in young people differed from those in uencing depression.Health behaviors such as sleep duration and alcohol consumption had a signi cant impact on depression; income level in uenced suicidal ideation when not adjusted for depression.When the depression variable was included in the model, the factors in uencing suicidal ideation were subjective health, stress, and depression.Sex differences were prominent in depressive symptoms, but not in suicidal ideation; however, there was a similar trend, wherein more men tended to experience depression and have higher levels of suicidal ideation.
The distinct differences in factors in uencing suicidal ideation and depression in young people, along with the disappearance of the income level effect when adjusting for depression, may imply several conclusions.Although there is an association between depression and suicidal ideation, considering depression alone as a risk factor for suicidal ideation may underestimate the in uence of other risk factors.Previous research has extensively studied depression as a contributing factor to suicide, and a strong association between suicidal ideation and depression has been well-documented [16].However, it is important to recognize that suicide and depression have different outcomes despite sharing similar characteristics, and this distinction should be re ected in mental health policies.Only a small proportion of individuals with depression die by suicide, and a signi cant proportion of patients with severe depression do not have any suicidal thoughts [18].The proportion of suicides caused by mental health problems among suicide deaths in Korea is 51.5% among those in their 20s and 37.7% among those in their 30s [1].In other words, more than half of the suicides could be attributed to other issues.Furthermore, although both suicide and depression are closely related to psychological Pain [17], Psychological Pain is more strongly correlated with suicide than with depression [43].The depression observed in individuals who engage in suicidal behavior may be an expression of severe sadness that accompanies suicidal urges [17].Therefore, viewing suicide as simply a clinical outcome of depression may be ineffective in preventing it.Consequently, further research is needed to explore the relationship between depression and suicide ideation and the various social determinants that in uence both.
Interestingly, our results suggest that health behaviors such as alcohol consumption and sleep duration in uenced depression but had no effect on suicidal ideation.This nding differs from those of previous studies indicating the effect of alcohol consumption and inadequate sleep duration on suicidal ideation [22,30].Suicidal ideation is a complex in uenced by various environmental factors, suggesting that the impact of health behaviors on suicidal ideation may be indirect, unlike its direct in uence on depression.Furthermore, it is well-established that individuals with depression are more susceptible to compromised health behaviors [44].Individuals with major depressive disorder exhibit increased sensitivity to both physical and psychological pain, whereas those vulnerable to suicide experience an increased level of psychological pain perception and decreased level of physical pain [45], which could partially explain why health-related variables had a relatively greater impact on depression.More research is needed to fully understand the intricate mechanisms underlying these associations and develop targeted interventions for individuals at risk of both depression and suicidal ideation.
Another peculiar nding was that the risk of depression decreased with alcohol consumption, which aligns with the ndings of previous studies [46].Considering the positive impact of light/moderate alcohol consumption on mental health [47][48][49], it can be considered a stress-relieving method for young individuals.Additionally, the young Korean generation engages in alcohol consumption as a means of social interaction [50], which could encompass the effects of such social exchanges.However, as this study did not measure the quantity of alcohol consumption or the prevalence of solitary drinking, it has limitations in assessing whether young individuals engage in problematic drinking or whether alcohol consumption included social interactions.Therefore, it is necessary to conduct additional investigations that include the type and quantity of alcohol consumption.
Indeed, the nding that poorer subjective health status was associated with an increased risk of suicidal ideation highlights the importance of health as a crucial factor for young individuals.Numerous studies have demonstrated a correlation between subjective health and suicidal ideation [35,51,52].Young adulthood is when growth and development end and aging begins.During this period, many young people experience a rapid decrease in physical activity and adopt unhealthy eating habits, and the risks of various chronic diseases begin to emerge [53,54].As physical health improves, it has a positive impact on reducing suicidal thoughts [55].Therefore, to promote mental well-being, it is crucial that physical aspects of health are not overlooked.
Stress was identi ed as a factor in uencing both depression and suicidal ideation.This nding aligns with prior research demonstrating the negative effect of stress on mental health [52,56].In young adulthood, individuals experience various stressors.It is a time of transitioning from parental dependence and involves signi cant life changes such as education, employment, marriage, and parenthood.These diverse changes can act as stressors for young individuals and potentially contribute to their vulnerability to mental health problems [57].Therefore, it is necessary to consider stress as a common factor when formulating mental health policies.
Furthermore, a lower economic status was found to increase suicidal ideation when not adjusted for depression.This nding aligns with the notion that economic struggle plays a major role in suicide in young adults [1].The fact that only economic factors among the socioeconomic factors are relevant implies that economic status is a particularly sensitive aspect.Moreover, the nding that income level does not affect depression but only in uences suicidal ideation suggests that economic factors can serve as triggers for suicidal behaviors among Korean youth.Young adulthood is the period when individuals strive for nancial independence from their parents and begin to establish an economic foundation, making them vulnerable to economic issues [58].According to the Korean National Basic Living Security Act, the minimum cost of living for a single-person household, which is the basis for providing a living allowance is 623,368 KRW [59].Meanwhile, the average monthly expenditure for a single-person household in 2023 is 1,627,316 KRW [3].Although direct comparisons are di cult, as these statistics are not age-adjusted, considering that the cutoff threshold for the lowest-income group in this study was 1,300,000 KRW, it can be inferred that these individuals face economic di culties.Economic status is associated with social isolation, and a low economic status induces psychological distress which can lead to suicidal ideation [60].In recent years, risky asset investments such as stocks, virtual assets, and real estate have increased among the young generation in Korea, leading to an increase in economic inequality as well [58,61].These recent social phenomena, combined with factors such as recent interest rate hikes and the decline in the value of cryptocurrencies and real estate, exacerbate economic polarization among young people [62] and could potentially have an impact on suicidal ideation.
Furthermore, the nding that the effect of economic status disappeared with adjustment for depression suggests the underestimation of the effects of other factors.Therefore, to prevent young people from suicide completion in Korea, efforts should be made to include low-income groups in the national mental health care system.Among the suicide prevention policies announced in Korea this year, speci c policies targeting the youth include: 1) providing specialized counseling for youths with depression and anxiety and strengthening the coordination with mental health and welfare centers; 2) conducting surveys on the mental health status and suicide risks among youths exposed to abuse and school violence; and 3) enhancing the coordination between independent living support agencies and mental health and welfare centers to foster care independence in young adults [63].While there has been an increase in the number of policy items targeting youths compared to previous versions of suicide prevention policies, speci c and substantial details are still lacking.It is necessary to include measures in policies to identify economically vulnerable youths as potential high-risk groups.
Additionally, there is a need for a comprehensive review of the overall delivery system for public mental health services.Public mental health and welfare centers face limitations in providing continuous services owing to high demand and limited resources [64].Moreover, young people face di culties accessing mental health welfare services that operate during daytime hours because of school or work.
Although 25.6% of all suicide deaths and 30.1% of all diagnosed depression cases in Korea occur in the age group of 20-30 years, only 20% of this population is registered in public mental health welfare centers [2,4,65].Considering that registration is also open to individuals with severe mental disorders and those without any mental health issues, it can be inferred that there is an even larger gap between the national registration rate and the number of individuals who require management and support.Therefore, it is crucial to nd methods that allow universal access to mental health services, while effectively identifying potential target individuals.For example, if it became mandatory for low-income college students to undergo mental health screening as a requirement for national scholarships, it would be easier to identify potentially high-risk individuals.Additionally, regarding various government nancial products aimed at providing economic support to young people, such as the "young people hoping savings" or "young people leap accounts," instead of solely focusing on income and age criteria, making mental health screening tests mandatory could be considered.Therefore, exploring practical screening methods through policy coordination among government departments is crucial.
This study has a few limitations.First, since only monthly average income, excluding debts and assets, was surveyed, there are limitations in explaining economic status.Additionally, this study did not assess the exact amount of alcohol consumed, which could have accurately measured the effect of alcohol consumption.Therefore, further research is required to supplement these ndings.This study's strength is that it is a meaningful analysis of a cohort of 1,014 young individuals, who have thus far received relatively less attention, and identi cation of the factors in uencing their mental health.Moreover, signi cant differences in factors contributing to depression and suicidal ideation among young people were identi ed, providing evidence for formulating mental health policies.

Conclusion
Depressive symptoms in young Koreans, which have led to a signi cant increase in the suicide rate in recent years, are affected by health behaviors.Unlike depressive symptoms, suicidal ideation was found to be dependent on income levels.It is important to be cautious and not underestimate the in uence of other factors on suicide, as depression and suicide share similar symptoms, but are distinct issues.
Studies that consider these factors are expected to have more positive impact on suicide prevention policies.Furthermore, to prevent young people from attempting suicide, it is necessary to develop various policies related to income level.To improve depression, it is essential to create policies that strengthen health behaviors.Finally, despite the evident mental health crises among young people, there is insu cient research on this population.Therefore, further studies are recommended to con rm the similarities and differences between depression and suicidal behavior in the young population.

Table 1
Factors in uencing depressive symptoms were age, sex, alcohol consumption, sleep duration, and stress (Table

Table 2
Factors in uencing depressive symptoms