The importance of health behaviours in childhood for the development of internalizing disorders during adolescence.

Background: Poor mental health constitutes a considerable global public health burden with approximately half of all cases of poor mental health having their onset before the age of 14 years. The identification of modifiable risk factors early in life is therefore essential to prevention, however, there are presently very few longitudinal studies on health behaviours for mental health to inform public health decision makers and to justify preventive action. We examined the importance of diet quality, physical activity (PA) and sedentary behaviours in childhood for internalizing disorder throughout adolescence.

Methods: We linked data from a population-based lifestyle survey among 10 and 11 year old grade five students in the Canadian province of Nova Scotia with physician diagnoses of internalizing disorders from administrative health records. We applied negative binomial regressions to examine the associations of health behaviours with the number of health care provider contacts with a diagnosis of internalizing disorder.

Results: Of the 4875 students, 23.9% had one or more diagnoses for internalizing disorder between the age of 10 or 11 years and 18 years. The number of health care provider contacts with a diagnosis of internalizing disorder was statistically significant higher among students with less variety in their diets, and among students who reported less PA and more time using computers and video games. The number of health care provider contacts was also higher for girls, and for students with low self-esteem and from low-income households.

Conclusions: These findings suggest that diets and active lifestyles in childhood affect mental health during adolescence, and imply that succxessful health promotion programs targeting children's diets and activity will contribute to the prevention of mental health disorders in addition to the prevention of chronic diseases later in life.