Orexins, Psychosis, and Antipsychotics: A Systematic Review of Studies of Orexin Levels and the Effects of Dual Orexin Receptor Antagonists (DORAs)

Background/Objectives: Schizophrenia is a severe psychiatric disorder frequently characterised by sleep and circadian disturbances, which are closely linked to cognitive dysfunction, symptom exacerbation, and poor functional outcomes. A growing body of evidence implicates the orexin (hypocretin) system—an essential regulator of arousal, sleep–wake stability, metabolic processes, and motivated behaviour—in the pathophysiology and treatment response of psychotic disorders. We aimed to investigate the relationships between the orexinergic system and psychoses. Methods: On 3 March 2026, we searched the PubMed, Scopus, PsycInfo/Articles and Cinahl databases for studies dealing with the orexin system and psychotic disorders and treatment response. Results: We found 20 eligible studies reporting variable and inconsistent alterations in orexin signalling in patients with schizophrenia. Studies were mostly cross-sectional and heterogeneous in design. Antipsychotic medications interfere with orexin-dependent pathways, potentially contributing to both therapeutic effects and adverse outcomes such as sleep disruption and metabolic dysregulation. Conclusions: While evidence from preclinical studies could point to an influence of dopaminergic activity through orexinergic mechanisms, with possible attenuation of antipsychotic-induced motor side effects and improvement of attentional deficits associated with NMDA receptor hypofunction, the utility of dual orexin receptor antagonists (DORAs) in psychoses is unclear. Despite the high prevalence of insomnia in schizophrenia, its pharmacological management remains suboptimal, with current treatments often limited by reduced efficacy or tolerability concerns. DORAs, which are currently approved medications for the treatment of insomnia, represent a novel and mechanistically distinct therapeutic option that may improve sleep while modulating arousal- and cognition-related circuits relevant to psychosis.