Decreased CO2 saturation during circular breathwork supports emergence of altered states of consciousness

Altered states of consciousness (ASCs), induced e.g. during psychedelic-augmented therapy, show great potential to treat highly prevalent mental health disorders like depression and posttraumatic stress disorder. However, such treatment approaches are not widely accessible due to legal, medical, and financial limitations. In this study, we explore the potential of circular breathwork to serve as a non-pharmacological and hence more easily accessible alternative to engage similar therapeutic processes. Scientific studies investigating the effects of breathwork on mental health are only just emerging and the underlying physiological and psychological mechanisms are largely unknown. In this study, we aim to address these questions by for the first time tracking physiological and experiential dynamics throughout the time course of a breathwork session, comparing two popular forms of breathwork: Holotropic Breathwork® and Consciously-Connected breathwork. We show that a reduction in end-tidal CO2 pressure due to deliberate hyperventilation is instrumental in catalyzing ASCs during breathwork. The ASCs evoked by breathwork were comparable to those produced by psychedelics, and their depth predicted psychological and physiological follow-on effects, including improved well-being and a reduction of depressive symptoms. Further analysis showed that different breathwork traditions impacted physiological markers as well as experiential and psychological outcomes in a similar way. Our findings identify physiological boundary conditions in which ASCs can arise in a non-pharmacological context, offering insights into the functional mechanisms of breathwork as well as its potential as a psychotherapeutic tool