Psychedelics as a treatment for disorders of consciousness

Introduction

Disorders of consciousness (DoC) — including the vegetative state (VS) and the minimally conscious state (MCS) — are severe outcomes of acquired brain injury in which wakefulness may be present but conscious awareness is absent or only minimally detectable. A variety of interventions have been tried, from pharmacological agents (e.g. zolpidem, amantadine) to invasive neuromodulation (deep brain stimulation, vagal nerve stimulation) and non-invasive stimulation (transcranial electrical or magnetic stimulation), but none have produced consistently reliable improvements in conscious awareness or functional recovery. Parallel to this, a resurgence of clinical research into classic psychedelics has produced findings relevant to basic and clinical questions about consciousness. Scott and colleagues propose exploring psilocybin as a candidate treatment to increase conscious awareness in patients with DoC. Their rationale rests on two recent and convergent empirical observations: measures of brain complexity (as indexed by metrics such as the perturbational-complexity index, PCI, and Lempel–Ziv complexity, LZC) appear to track levels of conscious awareness, and psychedelic drugs robustly increase these complexity measures in healthy humans. The authors frame a research agenda to test whether psilocybin-induced increases in brain complexity could translate into increased conscious content or detectable behavioural signs of awareness in DoC patients, while acknowledging substantial ethical and practical challenges.