Lithium as a Phase-Stabilising Agent in Bipolar Disorder: A Resonance-Based Hypothesis within the Sympathetic Harmonic Resonance Framework

Abstract Lithium remains one of the most effective treatments for bipolar disorder, yet its mechanism of action remains incompletely explained. Existing biochemical models—focusing on neurotransmission, second-messenger cascades, and gene expression—account for lithium’s molecular interactions but do not fully explain its distinctive clinical profile, including bidirectional mood stabilisation, delayed onset, long-term prophylactic efficacy, and superiority over antidepressants in bipolar depression. In this paper, we propose a complementary, systems-level interpretation of lithium’s effects within the Sympathetic Harmonic Resonance Framework (SHRF). Under SHRF, bipolar disorder is conceptualised as a disorder of phase coherence across coupled biological oscillators spanning neural, circadian, metabolic, and gut–brain systems. Lithium is hypothesised to function primarily as a global phase-stabilising agent rather than a signal-specific modulator. We examine how lithium’s physicochemical properties support this role and outline experimentally testable predictions. This framework aims to unify disparate findings and generate new directions for psychiatric research.