Depressive symptoms and suicidal behaviours in adolescent non-daily smokers compared to daily smokers and never-smokers in Korea: National cross-sectional study.

Our findings suggest that non-daily smoking in adolescents was associated with risks for depressive symptoms and suicidal behaviours, and the association was more prominent in early adolescents. Careful attention on the mental health of adolescent non-daily smokers is needed because this is an increasing and easily overlooked group.