Theoretical considerations: the Avoidance-Endurance Model (AEM) of pain
The AEM of pain was developed in order to address FAR as well as ER as important mediators in the development and maintenance of chronic pain and disability (Hasenbring 2000). While earlier formulations of this model primarily focused on potential maladaptive consequences of these different pain responses, the current version of the AEM also hypothesizes adaptive short-term consequences (positive or negative reinforcement) that may be responsible for the maintenance of these reactions.
Basic assumptions underlying the AEM are as follows. In accordance with the psychophysiological model of anxiety (Lang 1970) loose relations are hypothesized for the cognitive, affective, and behavioural responses to pain. Further, comparable to the Dynamic Model of Affect (DMA, Davis and Zautra 2004), an opposite pattern of FAR and ER are expected to exist on distinct dimensions, implying that opposite features can be activated independently. This assumption is supported by evidence of distinct neural systems for opposite affects and cognitions (e.g. Hass and Canli, 2008). We hypothesize that each individual will show a specific pattern of cognitive, affective, and behavioural pain responses when confronted with pain and that only specific, highly rigid and time-stable pattern of cognitive, affective, and behavioural pain responses will contribute to the maintenance of pain in the long-term run. We suggest that FAR represent a specific and highly rigid pattern of pain-related fear, cognitions of catastrophizing and helplessness, hopelessness, and behavioural avoidance (FAR pattern). In contrast, the AEM suggests that due to ER at least two different response pattern can be described influencing the maintenance of pain and disability. The distress-endurance pattern (DER) refers to marked thought suppression, emotions of anxiety and depression and to task persistence in spite of pain on the behavioural level. The eustress-endurance pattern (EER) refers to ignoring pain sensations and minimizing the meaning of pain experiences and marked task persistence behaviour, often accompanied by high scores on positive mood despite pain. Furthermore, an adaptive response (AR) pattern is suggested to be characterized by cognitions of sensory monitoring without ongoing negative affects, by a high degree of flexibility between avoidance and endurance responses to pain, supporting the effect of biomedical treatments. Finally, we suggest that there are a number of psychoneurobiological pathways from acute to chronic pain for FAR and ER that can be explained via learning conditioning theory in the long-term as well as maintaining mechanisms in the short-term.