EMO-PAIN – Mental comorbidity, interoception and emotion regulation in chronic pain patients

Chronic pain is highly prevalent and puts significant strain on the individual and the society. There is abundant research documenting a strong link between chronic pain and poor emotional health. Persistent pain commonly co-occurs with emotional disturbances like elevated levels of negative affect and is associated with high rates of mental disorders. Yet, even though persistent pain is a common human experience and the association between chronic pain and emotional disturbances is well established, the genesis of many pain conditions is still poorly understood. In addition, the knowledge about factors driving the relationship between persistent pain and poor emotional health is limited. It has been suggested that identifying shared mechanisms affecting both chronic pain and emotional problems may help explain this co-occurrence, and that this knowledge is crucial for informing and advancing the treatment of persistent pain. This thesis aims at improving the understanding of the association between chronic pain and poor emotional health by investigating the comorbidity between persistent pain and mental disorders, and examining emotion regulation and interoception, two factors potentially involved in the development and maintenance of both chronic pain and emotional problems. In Study I, we addressed the need for an up-to-date account of the prevalence of mental disorders in chronic pain based on the latest diagnostic criteria and investigated the point and lifetime prevalence of a broad range of mental disorders according to DSM-5 in patients with persistent pain receiving treatment at a specialized tertiary pain hospital. The point and lifetime prevalence estimates of any mental disorder were 57.2% and 77.9%, respectively. Substance-related and addictive disorders (26.2%), somatic symptom and related disorders (17.9%), depressive disorders (17.2%) and anxiety disorders (15.9%) were the most prevalent diagnostic groups of current mental disorders. Current mental health comorbidity was associated with elevated levels of pain catastrophizing and poorer outcomes of health-related quality of life. In Study II, we examined the role of within-day affective instability, an indicator of emotional dysregulation, in the experience of chronic pain using the day reconstruction method. Specifically, we investigated the relationship between within-day affective instability and within-day measures of pain disability and pain severity in a sample of patients with chronic pain and tested whether these associations changed over the course of an extant inpatient interdisciplinary multimodal pain therapy program. Within-day negative affect instability significantly moderated the relationship between within day pain severity and within-day pain disability. That is, when negative affect was more unstable the experience of pain severity was more strongly associated with the experience of pain disability within the day. Moreover, while within-day pain disability significantly decreased from baseline to post-treatment, we found that the moderating effect of negative affect instability remained stable over the course of the treatment. In Study III, we investigated interoceptive processes and their link to symptom report in patients with chronic pain. Focusing on cardiac interoception, we examined the assumptions of the perception-filter model concerning the processing and perception of afferent bodily signals. Relying on psychophysiological and behavioral data, results provide no support for the assumptions of the perception filter model. Symptom report, i.e., pain intensity, was not associated with an increased accuracy to detect cardiac signals. Altogether, the results of this project corroborate the evidence of a high co-occurrence between chronic pain and mental disorders, and in light of the adverse effects of this comorbidity observed, emphasize the need for addressing mental comorbidity in the treatment of chronic pain. Additionally, the findings support the assumption that the ability to regulate emotions is important when adjusting to chronic pain and suggest that targeting emotion regulation skills in the context of pain management may be beneficial. Our results challenge the assumption of a generally increased perception and detection of afferent internal bodily signals across different modalities in chronic pain. Basic research focusing on the investigation of interoceptive processes concerning symptom-specific modalities is needed to elucidate the clinical contribution of interoceptive alterations to the development and maintenance of chronic pain.