An epidemiological investigation of physical-mental multimorbidity: Findings from the 2014 Ontario Child Health Study

Abstract

Children living with chronic physical illnesses such as diabetes and epilepsy, are at increased risk for developing mental illness. The co-occurrence of at least one physical and at least one mental illness, known as multimorbidity, is not surprising as children living with physical illness and their families endure financial and psychosocial challenges, predisposing these children to experience mental health declines. Child multimorbidity is common. Approximately 25% of children live with physical illnesses that require long-term management and as many as 58% of these children are also diagnosed with a mental illness. The effects of multimorbidity are pervasive, burdening children, families, and the health, social and educational systems. Thus, there is a pressing need to address the mental health challenges of children living with physical illness. A proactive, preventive, public health approach requires a comprehensive understanding of child multimorbidity in a Canadian context.

Despite the underlying risk of mental illness across various physical illnesses, child mental health research often excludes childhood physical illness as a determinant of mental illness. Of the research that does exist, samples include older adolescents and young adults with chronic physical illness or include high-risk clinical samples. Research using epidemiological samples, inclusive of young children, has not been conducted since the seminal 1983 Ontario Child Health Study. As survivorship of children living with chronic physical illness has substantially increased with these children living well into adulthood, and as the designs and needs of healthcare and mental health care systems have changed since 1983, this research answers calls to the public health concern of child multimorbidity.

To address these knowledge gaps, the following dissertation identified which factors influence the association between chronic physical illness and mental illness (any, mood, anxiety, behavioural and neurodevelopmental disorders), including mediating and moderating factors, and examines differences in mental health service contact based on child health status (healthy, physical illness only, mental illness only, and multimorbid). Three distinct studies, with each study examining one of these main dissertation objectives, have been written for publication. These studies made use of data from the 2014 Ontario Child Health Study-a cross-sectional, epidemiological study of 10,802 children aged 4 to 17 years from 6,587 households from across 240 neighbourhoods.

1) Study 1 objectives included: a. Estimating the lifetime prevalence of childhood chronic physical illness and the six-month prevalence of mental illness and multimorbidity in children; b. Quantifying associations between physical illness and mental disorder, including number of illnesses; and c. Examining factors associated with mental disorder, after adjusting for chronic physical illness. 2) Study 2 objectives included: a. Examining moderating effects of child sex, age, health functioning, mental health service contact, and household income on associations between physical and mental illnesses; and b. Exploring the potential mediating effect of family functioning on physical-mental multimorbidity. 3) Study 3 objectives included: a. Estimating the six-month prevalence of health status and types of mental health service contact; b. Quantifying adjusted associations between child health status and type of mental health service contact; and c. Quantifying adjusted associations between child health status and number of different types of mental health service contacts.

In a sample of 10,303 children, the first manuscript estimated childhood chronic physical illness to be 27.8%, while 14.8% of children had mental disorder and 5.4% had multimorbidity. Physical illness was not associated with mental disorders. An ordinal regression illustrated children with two physical illnesses, as compared to no physical illnesses, had increased odds for having any, mood, and anxiety disorders. There were no associations found between children with one or three or more physical illnesses and mental disorders. Notably, health functioning demonstrated a dose-response across health status categories, with healthy children having highest scores and multimorbid children having lowest scores. These findings demonstrate the need for targeted and routine mental health screening in youth with two physical illnesses. Preventative mental health interventions should focus on preventing declines in health functioning.

The second manuscript used the subsample of index children (n=6,242). Physical illness was associated with increased odds of mood disorder. Health functioning moderated physical-mental illness associations, such that better health functioning in children with physical illness versus without physical illness, had higher odds for any mental illness, anxiety disorder, and attention-deficit hyperactivity disorder. There were no associations found in children with poorer health functioning and physical illness. No other child or household factors moderated associations and family functioning did not mediate physical-mental multimorbidity. These findings suggest physical-mental multimorbidity is nuanced, with differential effects of physical illness on childhood mental illness. Targeted mental health screening is needed for children living with chronic physical illnesses resulting in better health functioning.

The third manuscript estimated 21.4% of children had mental health service contact within the last six months. Regardless of child health status, contact was highest in school-based settings. Children with multimorbidity had higher odds for having every type of mental health service contact (any, general medicine, urgent medicine, alternative, school-based, and specialized mental health) than healthy controls. A dose-response was also observed, such that the number of types of mental health service contacts increased from physical illness to mental illness to multimorbidity. These findings support mental health resource allocation for school-based services. Further research is needed to understand barriers and facilitators of mental health service use including integrated health and mental health care for children with multimorbidity.

The findings from this dissertation fill critical knowledge gaps in child physical-mental multimorbidity research. Taken together, these findings show health functioning and not just the mere presence of physical illness is important to consider when examining the nuances and impact of physical illness on child mental health. Moreover, findings show mental health-related contact is similar across child health status. Findings also inform policy, intervention, and clinical research directions. From a policy lens, resources should be allocated to school-based mental health services. Universal mental health intervention efforts, regardless of child health status, should focus on preventing overall-health functioning declines. Regular mental health screenings for children living with chronic physical illness should occur, with early intervention efforts aimed at reducing the incidence of multimorbidity. Vigilant and routine screening is needed for children living with two physical illnesses and for children with better health functioning. Future longitudinal research is needed to elucidate mediating factors in physical-mental multimorbidity. Given proper supports within integrated health services, the incidence and impact of child multimorbidity can be reduced and children living with physical illness can have improved mental health outcomes.