RESUMO
Chronic pain and depression are highly prevalent pathologies and cause a major socioeconomic burden to society. Chronic pain affects the emotional state of the individuals suffering from it, while depression worsens the prognosis of chronic pain patients and may diminish the effectiveness of pain treatments. There is a high comorbidity rate between both pathologies, which might share overlapping mechanisms. This review explores the evidence pinpointing a role for the ventral tegmental area (VTA) as a hub where both pain and emotional processing might converge. In addition, the feasibility of using the VTA as a possible therapeutic target is discussed. The role of the VTA, and the dopaminergic system in general, is highly studied in mood disorders, especially in deficits in reward-processing and motivation. Conversely, the VTA is less regarded where it concerns the study of central mechanisms of pain and its mood-associated consequences. Here, we first outline the brain circuits involving central processing of pain and mood disorders, focusing on the often-understudied role of the dopaminergic system and the VTA. Next, we highlight the state-of-the-art findings supporting the emergence of the VTA as a link where both pathways converge. Thus, we envision a promising part for the VTA as a putative target for innovative therapeutic approaches to treat chronic pain and its effects on mood. Finally, we emphasize the urge to develop and use animal models where both pain and depression-like symptoms are considered in conjunction.
RESUMO
BACKGROUND: Chronic non-cancer pain (CNCP) treatment's primary goal is to maintain physical and mental functioning while improving quality of life. Opioid use in CNCP patients has increased in recent years, and non-pharmacological interventions such as music listening have been proposed to counter it. Unlike other auditive stimuli, music can activate emotional-regulating and reward-regulating circuits, making it a potential tool to modulate attentional processes and regulate mood. This study's primary objective is to provide the first evidence on the distinct (separate) effects of music listening as a coadjuvant maintenance analgesic treatment in CNCP patients undergoing opioid analgesia. METHODS AND ANALYSIS: This will be a single-centre, phase II, open-label, parallel-group, proof-of-concept randomised clinical trial with CNCP patients under a minimum 4-week regular opioid treatment. We plan to include 70 consecutive patients, which will be randomised (1:1) to either the experimental group (active music listening) or the control group (active audiobooks listening). During 28 days, both groups will listen daily (for at least 30 min and up to 1 hour) to preset playlists tailored to individual preferences.Pain intensity scores at each visit, the changes (differences) from baseline and the proportions of responders according to various definitions based on pain intensity differences will be described and compared between study arms. We will apply longitudinal data assessment methods (mixed generalised linear models) taking the patient as a cluster to assess and compare the endpoints' evolution. We will also use the mediation analysis framework to adjust for the effects of additional therapeutic measures and obtain estimates of effect with a causal interpretation. ETHICS AND DISSEMINATION: The study protocol has been reviewed, and ethics approval has been obtained from the Bellvitge University Hospital Institutional Review Board, L'Hospitalet de Llobregat, Barcelona, Spain. The results from this study will be actively disseminated through manuscript publications and conference presentations. TRIAL REGISTRATION NUMBER: NCT05726266.
