Stefan Elbers

16 Chapter 1 which resulted in the start of the first pain management programme in the United States in 1978 (Gatchel et al., 2014; IASP, 2021b; Kaiser et al., 2017). Over time, facilities that offered these programmes continued to integrate new findings, such as the biopsychosocial model (Gatchel et al., 2014), and adapted to constraints of local policy-making and health care systems (Kaiser et al., 2017). At present, these types of treatment have evolved into interdisciplinary multimodal treatment (IMPT) programmes. These interventions feature interdisciplinary teams of health care providers with different professional backgrounds, which coordinate their services throughout treatment and work within one facility. The various disciplines share a biopsychosocial understanding of chronic pain (Kaiser et al., 2017). Activities always include active patient involvement and often consist of a combination of education, exercise, and (cognitive) behavioural approaches, including pain reconceptualization, psychological flexibility, extinction of pain-related fear, and gradual increase in valued daily life activities (McCracken & Vowles, 2014; Vlaeyen, et al., 2016). Despite these similarities, there are signs that IMPT programmes vary considerably concerning patient inclusion criteria, dose, and content (Waterschoot et al., 2014). Crucially, choices regarding duration or the inclusion of specific treatment modalities are often not reported, obscuring interpretation of the results (Morley et al., 2013). A second problem is that systematic reviews indicate a positive, but limited, effect of IMPT programmes, compared to control conditions, at follow-up (Chou et al., 2017; Kamper et al., 2015; Williams et al., 2020). A possible explanation for these small-to-medium effects is the difficulty of adhering to treatment principles over time. This hypothesis mirrors current ideas regarding the difficulty in successfully promoting sustainable change in health behaviours through interventions (Wood & Neal, 2016). Further, in contrast to other chronic health conditions, this problem of potential relapse has been a neglected topic for decades in the field of pain management (Backs-Dermott et al., 2010; Martins et al., 2020; Morley, 2008; Turk & Rudy, 1991). A possible explanation for this is the difficulty in delineating clear endpoints to define relapse in these type of interventions. By definition, IMPT programmes include various modalities that aim to achieve and maintain optimal wellbeing via multiple routes (Gatchel et al., 2014; Kaiser et al., 2017). As a consequence, these programmes are evaluated by a broad set of measurement instruments that cover a wide range physical, psychological and social health outcome domains (Kaiser et al., 2018). This is different from treating conditions where the focus on more concrete outcomes or behaviours allows for more precise criteria of relapse, such as substance abuse (return to uncontrolled usage), obesity (weight regain) and depression (presence of at least five depressive symptoms) (Backs-Dermott et al., 2010, Melemis, 2015; Martins et al., 2020).