An Epidemiological Study of Physical-Mental Multimorbidity in Youth: Une étude épidémiologique de la morbidité physique-mentale chez les jeunes.

Objective: This epidemiological study estimated the lifetime prevalence of chronic physical illness (i.e., an illness that lasted or was expected to last ≥6 months) and 6-month prevalence of mental disorder and multimorbidity (i.e., ≥1 physical illness and ≥1 mental disorder) in youth. Associations between physical illness and mental disorder were quantified, including the number of illnesses. Secondary objectives examined factors associated with mental disorder, after controlling for physical illness.

Methods: Data come from 10,303 youth aged 4-17 years in the 2014 Ontario Child Health Study (OCHS). Physical illness was measured using a list of chronic conditions developed by Statistics Canada. Mental disorders were measured using the OCHS Emotional Behavioural Scales. The Health Utility Index Mark III assessed overall functional health.

Results: Weighted prevalence estimates showed 550,090 (27.8%) youth had physical illness, 291,986 (14.8%) had mental disorder, and 108,435 (5.4%) had multimorbidity. Physical illness was not associated with mental disorder. However, youth with 2 physical illnesses, as compared to no physical illnesses, had increased odds of having any mental (OR = 1.75 [1.08, 2.85]), mood (OR = 2.50 [1.39, 4.48]) and anxiety disorders (OR = 2.40 [1.33, 4.31]). Mean functional health scores demonstrated a dose-response association across health status categories, with the highest scores among healthy youth and the lowest scores among multimorbid youth (all p < .05).

Conclusion: Chronic physical illness and mental disorders are prevalent in youth. Youths with 2 physical illnesses have a higher likelihood of mental disorders. Higher functional health scores protected against all mental disorders. Mental health interventions for youth should promote strong overall functional health.

Plain language summary title: Physical-Mental Multimorbidity in Ontario Youth.