Globally, depression is the most prevalent mental health problem among adolescents. In 2013, 7% adolescents aged 12 to 17 years in the U.S. experienced a major depressive episode in the last 12 months [1]. In Korea, approximately 22% male adolescents and 32% female adolescents showed depressive symptoms in 2014[2]. In particular, those in early adolescence were at an increased risk for psychological problems such as depression [3]. These psychological problems are associated with extensive physical, emotional, and cognitive changes during early adolescence, and become an important turning point in an individual's development [3]. Depression in adolescence leads to negative effects on physical health such as obesity, [4] as well as adverse social and academic problems [5]. Depressive symptoms in adolescents are significantly associated with suicidal thoughts and behaviors [6]. In addition, depressive adolescents tend to grow into adults with higher emotional stress, and increased alcohol consumption and smoking intensity [7]. Thus, we should identify the factors associated with depressive symptoms in early adolescence for early intervention.

Distorted body image might result in depressive symptoms in early adolescence [8]. Individuals in early adolescence might be sensitive to the perception of others' evaluation and social norms with regard to their body size and shape [9]. Thus, individuals in early adolescence might perceive their body size and weight based on a subjective evaluation rather than an objective measurement [9]. During early adolescence, body size and shape before puberty are considered ideal; however, physiological changes following puberty differ from this ideal [10]. Thus, those in early adolescence are likely to have a distorted weight perception and body dissatisfaction [11]. According to Demuth et al. [12], a negative body image including distorted weight perception and body dissatisfaction was associated with psychosocial distress. Similarly, White [13] presented a model that suggests that perceived changes in appearance might lead to body image emotions such as depression. Additionally, distorted weight perception and body dissatisfaction were considered risk factors for depression during early adolescence [14]. In previous studies, distorted weight perception and body dissatisfaction were more closely associated than objective weight and psychological well-being among adolescents [15]. Thus, individuals in early adolescence with distorted weight perception and body dissatisfaction might be at an increased risk for depressive symptoms regardless of their body mass index (BMI) and objective evaluation of weight. In particular, Korean societies tend to value physical appearance as the evaluation of an individual's competence and superiority [8, 16]. Thus, the effects of distorted weight perception and body dissatisfaction on depressive symptoms might be more severe among Korean adolescents than among adolescents in Western societies.

An individual's weight perception is developed based on the ideal body weight determined by cultural standards [17]. Western and Asian cultures have different cultural standards for the ideal body size of children [18]. While a slimmer body is considered ideal in Western societies, current Asian societies, including Korea and China, have two paradoxical standards for ideal body size with the coexistence of the traditional standard that prefers a slightly plump body, and the standard from Western societies [19]. With the shared ideal body weight norms of Western societies through mass media, current Asian adolescent boys including those in Korea and China selected large and muscular figures as having an ideal and attractive body shape, while adolescent girls chose a small and slim body as an ideal and attractive body shape [20, 21]. In these contexts, among adolescent boys, perceived underweight and desired weight gain might have negative effects on psychological distress such as depression. In contrast, adolescent girls with perceived overweight issues and desired weight loss had depression. According to Xie et al.[21], distorted weight perception and concern associated with negative body image might differ among adolescents based on gender. Similarly, Korean adolescent boys with perceived underweight had low self-esteem, while adolescent girls with perceived underweight had high self-esteem [22]. Distorted perception regarding body size and negative body image could contribute to depression through low self-esteem [9]. In these contexts, Kim et al. [23] suggested further studies to examine gender differences in the associations between actual and perceived weight and depression symptoms. However, identification of gender differences in the association of objective weight, weight perception, and body satisfaction with psychological health was limited in Korea. Thus, the purpose of our study was to investigate the associations between depressive symptoms and weight (BMI percentile), weight perception, and body satisfaction among Korean middle school students in early adolescence based on gender.

This study reports gender differences in the association between depressive symptoms and weight, weight perception, and body dissatisfaction. Interestingly, in our findings, the association of weight perception and weight satisfaction with depressive symptoms differed with gender. Depressive symptoms among adolescent boys were associated with the perception of being underweight, and a desire to gain weight after covariate adjustment; while depressive symptoms among adolescent girls were associated with the perception of being overweight or obese, and a desire to lose weight. In previous studies with Dutch and Chinese adolescents, the perception of being overweight was associated with depressive symptoms regardless of gender [27]. However, perceived underweight among young adolescent boys (8th grade) and perceived overweight among young adolescent girls were associated with depressive symptoms, while perceived weight was not associated with depressive symptoms among older adolescents (11th grade) [28]. Schiefelbein and colleagues proposed that adolescent girls and boys received different messages regarding socially ideal body images such as a small and thin body shape for girls and big and strong body shape for boys. Deviation from the ideal body shape due to physical changes during puberty might result in loss of self-confidence and lead to a depressed mood [28]. Similarly, boys with a perception of underweight show depressive symptoms and tend to be teased by their peers for their small body, and desire a muscular body [28]. In contrast, girls might experience more stress than boys because of weight gain and face external pressure to control their weight [20]. Korean societies also have different social standards regarding ideal body shape based on gender. For men and boys, a big and slightly plump body is considered healthy and strong, while a small and thin body shape is considered attractive and ideal for women and girls [20].

In particular, Korean societies traditionally emphasize the value of collectivism, and gives importance to equality for all. In a collectivistic culture, acceptability by social norms might be the most important evaluation standard for the appropriateness of an individual's characteristics [8]. In this connection, people who perceived themselves with regard to a collectivistic culture were more likely to engage in social comparison through cultural values that were associated with weight dissatisfaction [8]. Similarly, Asians such as Japanese might experience high weight dissatisfaction because of the collectivistic culture that emphasizes social conformity and the need to be socially accepted [29]. Furthermore, Korean adolescents would be dissatisfied with their bodies and experience a depressed mood if they perceived their body weight as inappropriate based on social norms regarding ideal body weight [30]. In a previous study conducted with Korean middle school students, adolescent boys with perceived underweight tended to have depressive symptoms even if they had normal weight [10]. Additionally, adolescent girls with a perception of being overweight reported increased depressive symptoms even though they had normal weight and were underweight [9]. In this study, while perceived underweight among adolescent boys is associated with depressive symptoms, perceived overweight among girls is associated with depressive symptoms. Thus, there are gender differences in weight perception and weight dissatisfaction associated with depressive symptoms in Korean middle school students. Therefore, to relieve depressive symptoms in adolescents, interventions targeting weight perception and weight satisfaction should consider gender differences in weight misperception and weight dissatisfaction.

Weight perception and weight satisfaction, regardless of weight, were significantly associated with depressive symptoms among Korean adolescents. Moreover, weight perception and weight satisfaction associated with depressive symptoms differed with gender. Perceived underweight among adolescent boys was associated with depressive symptoms, and perceived overweight among girls was associated with depressive symptoms. Thus, school- and community-based interventions for the improvement of correct weight perception and weight satisfaction to relieve depressive symptoms should consider gender differences in weight misperception and weight dissatisfaction.

This study has some limitations. First, we could not control the covariates associated with depressive symptoms among adolescents because of the limitations of the secondary data analysis. Original studies that can adjust the covariates are recommended to verify the association of weight, weight perception, and weight satisfaction with depression symptoms among adolescents. Second, our study only focused on the association of weight, weight perception, and weight satisfaction with depressive symptoms among individuals in early adolescence. However, the association could differ across the developmental stages of adolescence. Thus, further study is needed to identify the associations with early, middle, and late adolescence.