The research team based in Australia and the Netherlands found the prevalence of anxiety disorders in youth with CMCs was higher than that in the general population. Anxiety may also be associated with adverse disease-related outcomes for children and adolescents with these conditions.

"The issue of 'mental-physical comorbidity' (i.e., meeting diagnostic criteria for least one mental illness and one physical disease) is critical, with the combination of anxiety disorders and physical disease appearing to be particularly prevalent among youth, said lead author Vanessa Cobham, PhD and clinical psychologist at the University of Queensland and Children's Health Queensland's Child and Youth Mental Health Service, Brisbane, Australia.

"Associated with significant implications, the combination of anxiety disorders and a physical disease presents the potential for worsened physical disease outcomes. Health professionals working with children and adolescents with chronic medical conditions should routinely screen for the presence of anxiety disorders in order to provide the best possible care to these youth."

The review based on 53 studies included the examination of prevalence of anxiety disorders and disease-related outcomes across seven different CMCs in children and adolescents with an average age of 18-years or younger.

Twenty-nine studies investigated the occurrence of anxiety disorders and found that more-than-half of the identified studies relied on only one informant (either the youth themselves or parent) in determining whether or not the youth met the criteria for an anxiety disorder. This was seen as the most significant limitation regarding the pervasiveness of an anxiety disorder.

While it is likely these studies underestimate the occurrence of anxiety disorders, the authors did find however that across all CMCs the anxiety prevalence rates were high: affecting approximately 20% to 50% of youth. In studies that included a healthy control group, rates of an anxiety disorder were substantially higher among patients with all CMCs. Across all CMCs, the rate of anxiety disorder was higher than the global prevalence rate of 6.5% as previously reported by Polanczyk and colleagues.

The remaining 24 studies examined the impact of anxiety on disease-related outcomes. No studies were identified for disease-related outcomes for epilepsy or congenital heart disease, however the authors reported that anxiety was associated with:

• poorer symptom control, school absenteeism, and higher rates of smoking in youth with asthma;
• increased disease activity in youth with inflammatory bowel disease;
• greater pain in youth with juvenile idiopathic arthritis; and
• longer lengths of hospitalizations in youth with sickle cell disease presenting in vaso-occular crisis.

The most significant and common limitations in relation to the question of the impact of anxiety on disease-related outcomes were the cross-sectional design of most studies and the fact that almost all studies relied on one informant only in assessing both anxiety and disease-related outcomes.

The evidence for youth with diabetes was inconsistent, with some studies reporting a negative impact of anxiety on metabolic control and treatment adherence and other studies reporting a positive association between elevated anxiety and treatment adherence.

While evidence that anxiety is associated with adverse disease-related outcomes in these youth, more longitudinal research is needed to delineate the impact of anxiety on child outcomes, Dr. Cobham and her team concluded. It is recommended that health services routinely assess for anxiety disorders among youth with CMCs. Psychometrically validated anxiety questionnaires (both parent and youth versions) are likely to be a feasible means of screening for anxiety disorders.