We live in a society that valorises speech and treats silence as a harm to be broken. In mental health discourse, this assumption runs especially deep. Silence is medicalised as a symptom, pathologised as a cause, and targeted by campaigns urging people to open up. Silence in Mood Disorders challenges this consensus, arguing that the dominant understanding of silence in mental illness is not only conceptually impoverished but potentially damaging to the very people it claims to help. Drawing on first-person accounts of depression and bipolar disorder alongside phenomenology, social epistemology, and silence studies, this book shows that silence in mood disorders is a far more diverse and complex phenomenon than prevailing assumptions allow. To make sense of this diversity, the book develops a set of interconnected conceptual resources for thinking about silence. Central among these is an account of silence as a fragile, embodied, and epistemically significant human capacity, whose disruption may take different forms in depression and mania. These resources are then used to suggest how mental health research, clinical practice, policy, and activism might respond to silence with greater care and discernment. Silence in Mood Disorders will appeal to scholars and advanced students in philosophy of psychiatry, phenomenology, and social epistemology, and will reward anyone working in mental health research, the medical humanities, or disability studies.