A survey was conducted to assess physical activity, depression, and sense of coherence among early adolescents. This study used a cross-sectional sample of 12,086 students(G5-G9)from 28 public elementary schools and 22 public junior-high-schools in Japan. A total of 9,424 students(G5-G8)were surveyed from December 2013 to December 2015 using the International Physical Activity Questionnaire ［資 料］ 発育発達研究 第 78 号 (IPAQ) -short form to measure physical activity (PA), the Depression Self-Rating Scale for Children (DSRS-C)for depressive symptoms, and the Sense of Coherence Scale-13-item version(SOC-13).Vigorous PA(VPA)of the G5 boys(4h 20 min)was significantly longer than that of the G5 girls(1h 30 min)and the VPA of the junior-high-school students increased significantly compared with that of the elementary-school students. The VPA of the G8 boys reached 6h 30 min, whereas that of the G8 girls approached 3h, which was a significant difference. Additionally, more junior-high-school students participated in sports-club activities than did elementary-school students.The mean DSRS-C score of the G5 girls(10.24±5.73)was significantly higher than that of the G5 boys (9.31±5.31). No other differences by grade, were found among the elementary-school students. The depressive symptoms of the junior-high-school students indicated they had a greater risk for depression than the elementary-school students did.The mean SOC score of the G8 boys(44.58±8.11)was higher(better)than that of the G8 girls (43.46± 8.30). Furthermore, the elementary-school studentsʼ score on the SOC was higher than that of the juniorhigh-school students；the score tended to decrease as the grade increased. Key words：adolescence, physical activities, depression, sense of coherence, questionnaire 思春期，身体活動量，抑うつ，首尾一貫感覚，質問紙法 Ⅰ はじめに 思春期は二次性徴による身体の変化や認識，感 情等の精神面など，急激な発育発達が起こる時期 であり，様々なストレスの原因となる出来事が増 える時期である．この思春期の健康問題として， 不登校，不定愁訴，自殺行為などが挙げられてお り，うつ病に関しても，わが国の思春期の子ども における有病率は 2.0-8.0％であり，大人とほぼ 同程度であるといわれている(傳田，2007) ．

A questionnaire survey was conducted to assess the physical activity, health-related QOL and depression of junior high school students. The subjects were 1,332 students from 5 public junior high schools in a certain city；valid responses were obtained from 1,289 students. The International Physical Activity Questionnaire（IPAQ）was used for assessing physical activity, the Pediatric Quality of Life Inventory （PedsQL TM ）for health-related quality of life（QOL), and the Depression Self-Rating Scale for Children （DSRS-C）for depression tendency.With regard to physical activity between males and females and among different grades, there was a significant difference in the amount of vigorous-intensity activity（in terms of days, hours, and total activity time of 1 week). However, no significant difference was observed in walking. In the different age groups, the difference was observed in moderate-intensity activity（time, total activity time of 1 week）and energy expenditure. No significant difference was observed between males and females in holiday time is sitting activity was not observed in the grades. With regard to health-related QOL, a significant difference was observed between male and female students in the emotional function. The percentage calculated for each grade revealed that the female students showed higher depression tendency than the male students and that the number of students exceeding the cut-off score, which was determined to indicate depression tendency, increased as they advanced to the next grade. While the score maintained around 30％ from the 1st year to 3rd year in the female students, it showed about 30％ only in the 3rd year in the male students. Furthermore, one in three male and female 3rd year junior high school students was determined to have depression tendency. Therefore, it is necessary to reconsider the current cut-off score when using it to assess junior high school students.Key words：Junior high school students, physical activity, health-related QOL, depression, questionnaire 中学生，身体活動量，健康関連 QOL，抑うつ，アンケート

This report provides an overview of the effectiveness of objectively measured physical activity, sports participation, and outdoor play on outcomes related to mental health and social skills in children and adolescents. Findings based on observation studies of longitudinal and cross-sectional design are inconsistent. On the other hand, several intervention studies with high intensity exercise programs indicated that intensity and amount of physical activity might provide a short-term benefit against depressive symptoms and anxiety. However, there are reports that psychosocial approaches confer effects similar to exercise programs. The effects of participation in organized sports clubs on mental health conditions such as depression, anxiety, self-esteem, self-efficacy, health-related quality of life, social skills (e.g., relationship skills), and coping ability were diverse. Notably, there could be unfavorable relationships in athletes exhibiting a higher performance. Meanwhile, participation in sports could represent a predictor of escalation in alcohol use as evidenced by longitudinal observation studies in adolescent, although there could also be effectiveness in terms of preventing use of illicit drugs. Lastly, active outdoor play under natural conditions without supervision also represented an effective approach to promote mental health (e.g., reducing depressive symptoms and building social skills such as self-regulation and coping skills in the face of difficult human relationships). We recognize that not only sports participation but also outdoor play under abundant nature environment could represent a significant physical activity to maintain mental and social health from childhood to adolescence.

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