A rich Haitian ethnopsychology has been described, detailing concepts of personhood, explanatory models of illness, and links between mind and body. However, little research has engaged explicitly with mental illness, and that which does focuses on the Kreyòl term fou (madness), a term that psychiatrists associate with schizophrenia and other psychoses. More work is needed to characterize potential forms of mild-to-moderate mental illness. Idioms of distress provide a promising avenue for exploring common mental disorders. Working in Haiti's Central Plateau, we aimed to identify idioms of distress that represent cultural syndromes. We used ethnographic and epidemiologic methods to explore the idiom of distress reflechi twòp (thinking too much). This syndrome is characterized by troubled rumination at the intersection of sadness, severe mental disorder, suicide, and social and structural hardship. Persons with "thinking too much" have greater scores on the Beck Depression Inventory and Beck Anxiety Inventory. "Thinking too much" is associated with 8 times greater odds of suicidal ideation. Untreated "thinking too much" is sometimes perceived to lead to psychosis. Recognizing and understanding "thinking too much" may allow early clinical recognition and interventions to reduce long-term psychosocial suffering in Haiti's Central Plateau.