The majority of the studies included children with various pain conditions (7/8). The age range was comparable across studies, ranging between 9 and 18 years. All studies included more girls than boys (60–89 % girls). Primary outcome variables included pain intensity in 6/8 studies, pain-related disability (8/8), school absence (8/8), and emotional distress (6/8). Two studies reported on posttreatment results; 4/8 studies reported on short-term effectiveness (ranging between 3 and 6 months). One study investigated long-term effectiveness (≥12 months).

Statistically reductions in pain intensity were reported by 6/8 studies. Two studies also reported clinically significant changes. All studies reported significant decreases in pain-related disability and school absence following intensive interdisciplinary pain treatment. Significant reductions in emotional distress were reported by 5/8 studies. Two studies reported also clinically significant reductions. In addition, Hechler et al. (2009) defined an overall improvement status by use of the construct of clinical significance (Jacobson and Truax 1991). Patients were classified as showing overall improvement if they did not show deterioration in any pain-related variable (i.e., in pain intensity, pain-related disability, and school absence) and had clinically significant improvements in one or both disability-related variables (pain-related disability or school absence). All other patients were classified as showing no overall improvement. Of their sample, 55 % were assigned to the group with overall improvement 3 months following treatment.

In summary, all studies provide evidence of the short-term effectiveness of intensive interdisciplinary pain treatment.

The research group of the German Paediatric Pain Centre (Dobe et al. 2011; Hirschfeld et al. 2013) investigated the long-term effectiveness of the intensive interdisciplinary pain program with two research questions: First, what was the degree of change in primary outcome variables 12 months following treatment? Second, how stable were the achieved treatment effects over two assessment periods, i.e., 3- and 12-month follow-up (Hirschfeld et al. 2013)? They defined the following groups based on overall improvement status at 3- and 12-month follow-up: (1) “stable long-term improvers” (improved on both assessments), (2) “short-term improvers” (improved at 3-month follow-up only), (3) “long-term improvers” (improved at 12-month follow-up only), and (4) “children with unsuccessful treatment results” (not improved at either follow-up). They found that participants showed statistically significant reductions in all variables 12 months after treatment, such that they reported less pain, disability, and fewer school absences. Over the two time points, 53 (46 %) of the adolescents were “stable long-term improvers,” 16 (14 %) were “long-term improvers,” 22 (19 %) were “short-term improvers,” and 25 (22 %) had an “unsuccessful treatment outcome.”

To sum up, children with chronic pain are able to maintain accomplished positive changes 12 months following treatment. Approximately 50 % recover quickly (after 3 months) and are able to maintain this status long term. Another 14 % take longer to improve but maintain this status as well. Approximately 20 % deteriorate over time, and another 20 % do not (yet) benefit from the intervention.

There are some methodological problems of the existing studies ranging from a heterogeneous definition of core endpoints (Maynard et al. 2009; McGrath et al. 2008) and, most importantly, a lack of control groups and randomization (Eccleston et al. 2003; Hechler et al. 2009; Maynard et al. 2009; Sherry et al. 1999). There are only five randomized controlled trials (RCT) available yet (Hechler 2011; Lanzi et al. 2007; Lee et al. 2002; Lommel et al. 2011; Wicksell et al. 2009) – compared to 12 RCTs in adult samples (Guzman et al. 2002). Four of the five RCTs, however, did not provide intensive interdisciplinary pain treatment as defined previously.

In the study by Hechler (2011), adolescents (aged 9–17 years) were randomly assigned to either immediate referral (fast track sample) or a 3-week waiting list (best practice sample). Assessments were made before treatment and 3 weeks following randomization, after the intervention group had completed the treatment. Main outcomes were pain intensity, pain-related disability, and school absence; trial compliance was considered as a secondary endpoint. Over a 19-month recruitment period, 120 adolescents were recruited and 1:1 randomized. Nine children of the intervention group discontinued treatment. Only the intervention group showed locally significant changes in all three core parameters. More children in the intervention group compared to the best practice group showed clinically significant changes in pain-related disability (22 % versus 6 %) and school absence (36 % versus 11 %). This pattern was not found for pain intensity. Significantly more children in the intervention group showed overall improvement (54 % compared to 16 %; Fisher p  <  .001; 95 % CI for incidence difference: 19–0.57 %). The study provides evidence that inpatient-based intensive interdisciplinary pain treatment improves pain-related disability and school absence in paediatric chronic pain patients.

Children and adolescents with chronic pain differ with regard to their pain intensity, pain-related disability, and school absence as well as emotional distress. These differences in the severity of the chronic pain problem have an important impact on the kind of treatment that may be required. For example, a child with high pain intensity but low pain-related disability and school absence may not necessarily be admitted to an inpatient-based treatment setting. The question of how the severity of the chronic pain problem should be graded in children is still unanswered. Which factors should be taken into account when assigning children to different degrees of treatment intensity?

In Germany, we refer children who display unsatisfactory treatment results in primary care to our inpatient-based treatment (see also Chap. 5 for a more detailed description). In addition, all patients meet the following criteria for inpatient admission in accordance to the medical service of the health-care insurances (Hechler et al. 2009):

In addition, at least three of the following five criteria have to be met to be admitted to the inpatient unit:

Unfortunately, the specificity and sensitivity of these criteria have not yet been investigated.

While there are assessment tools to grade chronic pain in adults, such as the severity grading system of Von Korff et al. (1992), the Chronic Pain Grading (CPG) adaptation of such a system for children and adolescents with chronic pain is scarce. In the CPG, pain severity is calculated based on an algorithm including pain intensity, disability days, and an overall judgment of pain-related disability.

Huguet and Miro (2008) applied the CPG to a sample of school children. They found that 37 % of their sample had chronic pain, but only 5 % reported chronic pain that was classified as moderate or severe. They further showed that increasing pain severity was associated with decreased quality of life, increasing visits to a doctor, and medication usage. A limitation of this study is the low number of children assigned to the higher CPGs; only 4 % (n  =  22) were experiencing moderate and only 1 % (n  =  6) high chronic pain severity.

Vowles et al. (2009) developed another severity grading system for adolescents, including psychological variables based on the Bath Adolescent Pain Questionnaire (BAPQ; Eccleston et al. 2005). It comprises four distinct groups differing in daily functioning, emotional functioning, family functioning, and development. While those results are promising with regard to a potential grading system for children and adolescents, the findings are hampered by the fact that they are based on children with musculoskeletal pain only and are specifically developed for the BAPQ, which is so far only available in English. Furthermore, the clinical applicability of this measure is limited due to the use of a rather complex algorithm for group assignment. Even though conducted in a clinical sample, this study did not test the utility of the measure for treatment assignment.