HaPpY's ambitious endeavor is to break the vicious cycle linking pain and mood disorders. The increasing number of patients with comorbidities poses an urgent need to improve their management. Among these comorbidities, chronic pain and mood disorders, two long-lasting disabling conditions that significantly reduce quality of life, could be cited first. Given the importance of this comorbidity, only research considering both pathologies in an integrative way can achieve the required insights into the underlying mechanisms that are necessary to identify novel diagnostic tools and treatment strategies. To respond to this health and societal emergency, a network of academic institutions and companies has been established to provide 15 early stage researchers (ESRs) with a top quality international training programme. The HaPpY network is comprised of higher education institutions with very well-established track records of scientific and academic excellence, and of research institutes with significant experience and cutting-edge approaches in fundamental research on mood disorders or/and pain. To ensure that discoveries in fundamental research can swiftly move toward clinical settings, to the benefit of patients and society, our consortium is enriched by clinical centres, companies and other non-academic partners. This consortium thus enables a unique research and training programme by combining and integrating the complementary strengths of each partner.