Data and study population

The Korean Study of Women’s Health Related Issues (K-Stori), was a nationwide survey designed to investigate broad health issues among Korean women according to five stages in the life cycle of women. Specific questionnaires were designed for each of the five stages (adolescence, childbearing, pregnancy & post-partum, menopause, and older adult), since life cycle approaches have been found to be effective in understanding and managing health problems and health promotion plans. A pilot study was conducted to determine the feasibility and validity of the survey [ ].

Per each stage in the female life cycle, 3000 women (total 15,000) were randomly sampled for a reliable and representative research design. For random sampling, a multi-level, stratified, probability-proportional statistics extraction method was used as a sampling framework using the 2010 Population and Housing Census. In order to generalize the survey results, the subjects were selected by random sampling for 16 cities and provinces (seven special and metropolitan cities, and nine provinces). The extraction method was used to stratify recruits by region and dong-eup/municipal district, after which 200 households were sampled. A sample of 15 households was extracted from each sampling area, in which the principle was to survey female household members aged 14–79 years in each sample household. Interviewers visited each of the 15 extracted households. However, for adolescents, the questionnaire was conducted via an online survey to minimize distortion of responses to sensitive health behavior items [ ].

This survey was conducted from April 2016 to June 2016. Subjects who did not agree to participate in the survey and those with difficulties communicating were excluded. The survey response rate is 40.4 %. The study was approved by the Institutional Review Board of the National Cancer Center, Korea (Approval no: NCC2016-0062). The details of K-Stori have been described elsewhere [ ].

We investigated the health status, behavior, and perceptions of Korean adolescent girls using an online survey. Of the 3000 adolescent girls who participated in the K-Stori survey, the study subjects were 2970 girls aged 14–17 years (middle school, second grade and high school, second grade), after excluding 30 participants before menarche.

Dependent variables

Depressive symptom was defined as the dependent variable of interest. The Patient Health Questionnaire (PHQ-9) is a self-report tool for screening and case finding of major depressive disorder (MDD) [ ]. The PHQ-9 is the most commonly used screening instrument for depression in primary care and other clinical settings [ ]. It consists of nine items that assess the frequency of depressive symptoms in the past two weeks. Subjects were asked how often, over the last 2 weeks, they have been bothered by each of the depressive symptoms. Response options are “not at all”, “several days”, “more than half the days”, and “nearly every day”, scored as 0, 1, 2 and 3, respectively. PHQ-9 scores range from 0 to 27, with scores of ≥5, ≥10, ≥15, representing mild, moderate and severe levels of depression severity [ ]. Psychometric properties of the PHQ-9 are well documented [ ]. We used the Korean version of the PHQ-9 [ ] We defined depressive symptom as mild to severe when the score is ≥ 5 in the nine-item scale [ ].

Independent variables

The primary independent variable was premenstrual syndrome. According to the International Classification of Diseases (ICD-10) of the World Health Organization and the American College of Obstetrics and Gynecology (ACOG), PMS was accessed if participants reported at least one of the following emotional and physical symptoms: breast swelling and tenderness, fatigue, bloating, lack of energy, appetite changes, sleep problems, headache, impulsivity, mood lability, depressed mood, anxiety, agitation, social friction, feeling “loss of control,” decreased concentration, and irritability [ , ]. Symptoms must be present during the five days preceding menstruation in each of the two consecutive menstrual cycles and must resolve within four days of the onset of menstruation without recurrence of symptoms until at least day 13 of the cycle [ ].

Age, body mass index (BMI), satisfaction with body image, smoking and drinking experiences, academic performance, and age at menarche were considered. BMI was calculated using participants’ self-reported height and weight. Participants were categorized according to criteria for Asians or generally applied definitions for the Korean population using BMI cut offs of <18.5 kg/m2 (underweight), <23 kg/m2 (normal), ≥23 kg/m2 (overweight), and ≥25 kg/m2 (obese) [ , ]. To assess adolescents’ body satisfaction, we asked the following question: “Are you satisfied with your current body weight or shape?” which can be answered by the options: “satisfied with both weight and shape,” “satisfied with weight,” “satisfied with shape,” or “satisfied with neither weight nor body type.”

Statistical analysis

First, we investigated the general characteristics of the study population and the prevalence rates of PMS and depressive symptom. BMI, body satisfaction, health behavior, and menstrual characteristics according to depressive symptom status were compared using the chi-squared test. Multivariable logistic regression analysis was used to investigate factors associated with depressive symptom and whether PMS was associated with depressive symptom. Odds ratios (ORs) and 95 % confidence intervals (95 % CI) were presented as an index of association. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Inc., Cary, NC, USA).