There is little data about assessment of general health among Iranian adolescents. We aimed at studying the general health of 3rd grade high school students in Tehran.

In a cross sectional study representative sample of 3rd grade high school students were selected using multistage random sampling taking each school as cluster. The General Health Questionnaire (GHQ12) was administered to the students in absence of the teachers. Questions about physical activity and demographics were also included. The cut off value for GHQ score was determined using Receiver Operating Characteristic (ROC) curve against self reported general health taken as gold standard. The scores equal or higher than the cut off were assumed as high.Proportion of the students with high GHQ score was calculated by age and sex. Comparison of the proportions was made using Chi square test.

Of 4842 students studied 55% were 17 and 45% were 18 years old. It included 2444 (56%) girls.The cut off of 4.5 for GHQ score was obtained. The area under the curve was 0.89 (0.95CI, 0.85-0.89, p<0.001) with sensitivity of 0.86 and specificity of 0.69.The proportion of high GHQ was 46% and the girls had higher (49.8% versus 40.5%) (p<0.001). The high GHQ score in 18 years old was higher than that for 17 years old students (928,48.2% vs.1040,43.6%, p<0.005). Those who assessed their general health as"very good" had lower GHQ score than those who assessed themselves as "very bad" (410, 29.4% vs. 54, 84.5%) (p=0.000). Students with higher level of physical activity had lower GHQ score comparing with those with lower physical activity (490,35.4% vs. 660,63.5%) (p=0.000).

Proportion of minor mental disorders is high in Adolescents. Girls are more vulnerable to the mental disorders. Better mental health was associated with higher levels of physical activity.