This study found high somatic comorbidities in a large naturalistic sample of 276 children with broad psychiatric diagnoses, including NDD, affective disorders, eating disorders and psychosis. The primary somatic comorbidities were 1) problems associated with food intake, including overweight, obesity and vitamin D3 deficiency and 2) sleeping problems, mainly insomnia. Our findings indicate that somatic comorbidities are widespread in children and adolescents with psychiatric disorders. Assessing various somatic comorbidities in a sample consisting of several child psychiatric disorders, allowed to see its broad variation including problems with weight, problems related to food intake, vitamin D3 deficiency (<50nmol/l), insomnia and minor physical anomalies.
With respect to problems in weight 12.0% of our sample was obese compared to 2.5% in the general Dutch population in the same period of this study [29]. Similarly, the percentage of overweight was 19.9%, compared to 14.2% of children in the general Dutch population [29]. These percentages increased for children using antipsychotic medication (25% for overweight children and 13.5% for obese children). These findings are consistent with previous studies. For example, in children with NDD, prevalence rates of overweight vary between 11-34% (our study 20.2%), and for obese children, between 12-23% (our study 12.2%) [4,5, 30-32].
A recent meta-analysis indicated that obese children are more at risk for depression than normal-weight children with a prevalence of 10.4% [33]. In the opposite direction, our results displayed a prevalence of 12.5% of obesity among children with depression and anxiety disorders (affective disorders). Likewise, the same symptoms related to lifestyles, such as sedentary habits, disordered sleep, insufficient physical activity and dysregulated food consumption, are common in obese children and children with affective disorders [34]. For an optimal development of children, it is essential to be aware of these symptoms and to address both psychiatric and somatic conditions. As obesity is an important risk factor for cardiovascular disease during later life, it is important to be aware of the risk factors in children, such as some types of medication, the psychiatric disorder itself, genetic variations with obesity and lifestyle related factors [35].
Furthermore, our study showed a prevalence of vitamin D3 deficiency (<50nmol/l) in the whole group of children with psychiatric disorders of 73%. This is much higher compared to reported 30% in the general population of Dutch children [36]. Vitamin D3 deficiency is associated with a range of adverse somatic and psychiatric outcomes (cardiovascular, diabetes, cancer, depression, NDD, psychosis and dementia) and might be a risk factor for impaired brain development [37, 38]. Reversely, vitamin D3 deficiency could be due to unhealthy lifestyle such as poor diet quality, being overweight and reduced exposure to sunlight by an imbalance between indoor and outdoor activities, which may be more common in children with psychiatric disorders [39, 40]. Additionally, a recent study revealed an inverse association between BMI and vitamin D3 levels in children with ASD and internalizing disorders [41], which is in line with studies in the general population [42, 43]. However, the underlying associations of vitamin D3 deficiency in somatic and psychiatric disorders are still poorly understood and questions for supplementation and lifestyle intervention remain.
The second main finding is the high rate of insomnia in our population (66% ) compared to primary school-aged children (5-30%) and adolescents (4-13%) in the general population [44]. Insomnia is the most common sleep disorder in children and is primarily characterized by difficulty initiating or maintaining sleep and/or poor sleep quality, which results in significant impairments in daytime functioning [45, 46]. Sleep problems are complex and viewed as part of neurologic and psychiatric disorders (e.g., ASD, affective disorders, epilepsy, psychosis, migraine) [45-47]. For some psychiatric disorders sleep problems are also part of the criteria itself (e.g., depression and anxiety disorders) [46].
Several studies show that estimates of insomnia are higher in pediatric populations with psychiatric diagnoses, including ADHD, ASD, anxiety and depression which is in line with our findings [47, 48]. For instance, our study found that insomnia in children with NDD was comparable with the existing literature (50-80%) [47, 49, 50]. Also, for insomnia in children with affective disorders, similar rates are found: in our study 81% compared to 75 - 90% for depression and anxiety in previous studies [46, 48, 51]. Notably, in case of insomnia, the symptoms of depression or anxiety disorder are even more severe [46, 48, 51]. In addition, cognitive behavioral therapy for insomnia provides a non-pharmacological option for improving sleep in psychiatric patients [18]. This is also relevant for children with psychiatric disorders in which the relationship between sleep and behavioral interventions has not been fully elucidated.
The clinical assessment further showed a high rate of minor physical anomalies (MPA) in children with NDD (53%) and psychosis (55%), which is also consistent with the literature [52, 53]. While a single MPA is not uncommon in the general population, a greater number of MPAs is associated with somatic comorbidities and underlying genetic variations [54]. As such, careful analysis of the combination of NDD, childhood psychosis, somatic comorbidities and MPA requires an simultaneous assessment to consider referral to a clinical geneticist [14].
Besides the physical outcomes, 66% of the children in our study did have a primary caregiver with a psychiatric diagnosis and 56% had been exposed to stressful life events (SLE; divorce of caregivers, death of caregiver, serious illness to family members, physical and/or sexual abuse, bullying at school). The Netherlands Mental Health Survey and Incidence Study [55] revealed an estimation of 350 Dutch children in 10.000 residents with a caregiver with a psychiatric diagnosis; the National Survey of Children's Health in the United States estimated that 7.2% of the US children had at least one caregiver with poor mental health [56]. For SLE, there is no single definition of what an SLE is and the impact may vary per event and child [57]. The reported prevalence of SLEs in children is high and varies between studies [58, 59]. Poor mental health among primary caregivers and exposure to SLE are associated with poor mental and physical health in children across the lifespan [56- 59].
Unfortunately, accurate and timely somatic assessment in children with psychiatric disorders can be challenging due to atypical presentation of symptoms, difficulties in describing and/or expressing subjective experiences or symptoms and insufficient expertise about somatic comorbidities in this population [11]. In line with our study, Agnafors et al (2019) showed associations between a wide range of psychiatric and somatic disorders across all types of conditions and across all ages in a register-based study [12]. This warrants the question to implement simultaneous assessment of somatic and psychiatric symptoms in children and adolescents with psychiatric diagnoses.
Among the strengths of our study is the extensive assessment of the somatic comorbidities of a relatively large number of children and adolescents with different psychiatric disorders. This showed a broad variation of comorbidities, underscoring the importance of routine somatic assessment in children with psychiatric disorders. Second, the somatic and psychiatric assessment was performed with great scrutiny and based on the assessment of two clinical experts (independent child and adolescent psychiatrists) and the psychiatric diagnoses were based on an evaluation by a multidisciplinary team. Additionally, the somatic assessments were carried out in a standardized way, allowing consistent and reliable collection of data. Third, we ran additional analyses with different variables to determine the influence of these variables (gender, age, medication and SES) on the physical examination and laboratory findings.
There are also several limitations regarding this study. First, lack of a matched control group may limit the specificity of our findings. However, prevalence rates from children from the general population were available.. Given the remarkable differences with this norm population, our general concerns about the high rates of somatic concerns in children with psychiatric disorders appear valid. Second, all children in this study were recruited in a child psychiatric center, which may introduce ascertainment/selection bias. A third limitation is that, although we have included children with various child psychiatric disorders, the number of patients in some specific diagnostic categories was small(e.g. psychosis and eating disorders), not allowing additional analyses to explore potential relationships between specific diagnosis and somatic comorbidities. A fourth limitation is the cross-sectional design which does not allow for further exploration of intricate relationships between psychiatric and somatic concerns over time.
We recommend that future studies investigating physical health in child and adolescent psychiatric populations collect longitudinal data in large samples of children and typically developing peers, including those with intellectual disabilities. At a broader public health level, research is required into the effectiveness of interventions that promote a healthy lifestyle, especially in child psychiatric population. Also, the role of vitamin D3 in psychiatric and somatic diseases needs further exploration, for instance, how it relates to other health factors (such as BMI, age, gender, diet, ethnicity, season, etc.), but also what the effects of supplementation are in relation to diagnosis. Furthermore, research of underlying genetic variation may provide deeper insight into patient (sub)groups more susceptible to mental and physical health problems than others. Ultimately, this may guide personalized treatment approaches.
In conclusion, the findings of this study underscore the high prevalence of somatic comorbidity in children and adolescents with psychiatric disorders and highlight the importance of standardized somatic screening in this group. The primary somatic comorbidities, including higher-than-healthy weight, vitamin D3 deficiency and sleep problems, may be strongly related to lifestyle factors and future studies may need to address this. As such, the findings of this study suggest that mental health professionals may need to asses and treat somatic comorbidities or refer for adequate treatment. Clinicians must address mental and physical health, to ensure maximal well-being and the best possible outcomes for children and adolescents with psychiatric illnesses.