Health service use for young males and females with a mental disorder is higher than their peers in a population-level matched cohort

This study identified that young people hospitalised with a mental disorder of both sexes had a higher risk of further hospital admission for either their mental disorder or other physical conditions than their matched peers during the study period. The risk was over 10-fold higher for males with psychotic and anxiety disorders, and was higher for both males and females with cognitive and behavioural delays, intellectual disability, and mood disorders compared to peers. Young people with ≥ 2 co-occurring mental disorders had the highest risk of further hospitalisations compared to their matched counterparts.

Hospital admissions of young people with mental disorders are increasing in a number of high-income countries [15, 25, 26]. This increase is at least partly due to increasing awareness and diagnosis of mental disorders in young people, along with a potential increase in risk factors for young people, including poor psychological health, genetic vulnerability stemming from a family psychiatric history, and adverse environmental conditions and interactions [25]. In the US, mental disorders were the most commonly given reason for hospital admissions of young person who had existing health conditions [27]. Young people with a mental disorder in the US were also more likely to have multiple hospital visits compared to young people hospitalised for other health conditions [15].

In the current study young males and females diagnosed with psychotic disorders had a 13- and 9-fold increased probability of further hospital admissions than their matched counterparts, respectively. This is consistent with the findings of a recent systematic review and meta-analysis, which identified that psychotic disorders were associated with repeat hospitalisations among adolescents [28]. Similarly, psychosis was the most common principal diagnosis identified in a New Zealand study of admissions to a child and adolescent psychiatric inpatient unit [26]. However, the frequency of hospital admissions for psychotic disorders was not only related to the course of the illness itself, but can be influenced by factors such as adverse childhood circumstances, mental disorder among carers, and ongoing substance use, particularly the use of cannabis [26, 29].

Young people with an intellectual disability were identified as having more than a 10-fold higher risk of further hospitalisation than their peers, consistent with the other studies [30]. More frequent use of hospital services are due to both the behavioural disturbances associated with many forms of intellectual disability, and the existence of a range of comorbid physical disabilities and comorbidities compared to peers [31]. People with an intellectual disability can experience barriers to accessing primary health care, which can lead to their increased use of hospital services [31]. In fact, preventable hospital admissions are known to be more common among people with an intellectual disability of all ages compared to the general population [32].

This study found a seven- and nine-fold higher risk of further hospitalisation for both males and females with ASD compared to peers, respectively. This finding is consistent with studies elsewhere that found young people with ASDs were twice as likely to be hospitalised than the general population [33]. Young people with ASD can experience difficulties in social interactions, sensory processing, behaviour and communication, and often require treatment for co-occurring psychological comorbidities (commonly attention deficit hyperactivity disorder, anxiety and depression) and physical illness [33, 34] that can all contribute to their high healthcare needs and utilisation. Children with ASDs aged 1–8 years can experience a higher proportion of comorbidities than their peers and have a higher likelihood of being admitted to hospital and a longer hospital LOS than children without ASD [35]. Young people with ASDs can also experience difficulties in accessing primary care and report negative experiences with healthcare providers [34, 36].

In the current study, young people diagnosed with mood or anxiety disorders had a ten-fold higher risk of a further hospital admission than their counterparts. Depression among young people aged 13–17 years has been associated with increased healthcare use and associated treatment cost in the US [37]. In a Californian study of young people with a mental disorder aged 5–17 years, the most common reasons for admission were depression (27%) and anxiety-related disorders (14%) [38], possibly because of the higher incidence of self-harm associated with these disorders, as young people who self-harm or express suicidal ideas have at least twice the risk of hospitalisation than those without suicidal ideation [28].

Some young people are reluctant to seek mental health care for reasons such as the stigma associated with mental illness and poor mental health literacy [39, 40]. The accessibility, cost and availability of specialist services may also present a significant impediment to adequate mental health support for young people [39]. Moreover, mental disorders experienced by young people are often closely linked to their family environments, social circumstances and life events, which are not easily modified by healthcare interventions and may require other preventive and supportive measures, such as educational interventions [41]. Nevertheless, early detection and timely access to mental health services are important [17], as successful intervention for treatable mental disorders can have a lasting effect on the trajectory of a young person’s future mental health, social and educational performance. Promising interventions can involve symptom management, encouraging adherence to treatment regimes, developing a supportive environment and social network, and better access to primary care and specialist mental health services [29, 42‐44], which, along with early detection and timely access to mental health services [17], are important and are likely to strengthen a young person’s capacity to manage adverse situations.

Hospital admissions for treatment of mental disorders in young people are influenced by a number of factors, including both the availability of specialist hospital beds [25], hospital admission policies, and also the availability of community-based alternatives and care pathways [31]. In 2018-19, the majority of public hospital beds allocated for mental health admissions in Australia were for general adult services (71.4%; 5,002 beds), with only 4.3% (303 beds) allocated for child and adolescent services [45]. A further 1.0% (70 beds) were allocated for youth services in Australia in 2011-12 [45].

Further research could explore the type of co-occurring health conditions experienced by hospitalised young people with a mental disorder, as well as examining their health service use trajectories over time, including reasons for repeated readmissions and identification of factors influencing the frequency of health service use. The transition from paediatric to adult mental health services is an area of particular concern [46], and the effect of interventions in adolescence on later health service use is an area that deserves further investigation. A better understanding of unmet health service needs of young people with a mental disorder should be identified, as up to 38% of young people with a mental disorder indicated they had not sought or received treatment for their conditions from health professionals [39].

The strength of this study was that it was a large population-based study linking birth, ED visit, hospital admission, ambulatory contacts and mortality records over a 13-year period. However, there were some study limitations. In most cases, only comorbidities relevant to the admission are indicated in hospital diagnosis classifications, therefore it is possible that some comorbidities experienced by young people were not recorded. This is particularly likely for the comparison cohort, where not all had been admitted to hospital and, as a result, there was no opportunity to identify comorbidities, despite the three-year lookback period. The count of hospital readmissions was not disaggregated by mental and physical conditions, but as indicated in Supplementary Tables 3, mental disorders accounts for 20.3–28.3% of readmissions for young males and females, respectively. No assessment of data validity was able to be conducted and it is possible that there could be some data misclassification. A small number of residential postcodes could not be identified, which affected socioeconomic and regional classification of those cases.

The study only compared young people who had been hospitalised for a mental disorder, and did not include young people presenting solely to mental health professionals in private practice for treatment. In Australia, the threshold for hospitalisation for young people with a mental disorder is high, as there are comparatively few mental health inpatient beds for this cohort, and the main reasons for admission are concern for a young person’s safety, or for diagnostic clarification or treatment of a condition. Hence, hospitalised young people with a mental disorder in Australia are likely to be the most seriously affected, regardless of diagnosis and irrespective of the number of days spent in hospital. Information on visits to private hospital EDs were not available and information on ambulatory mental health contacts at public hospitals were only available from 2006.