This paper examines whether mental disorders can be understood as natural kinds. I argue that, at least in a strong etiological sense, this assumption is difficult to sustain given the current state of psychiatric knowledge. While paradigmatic natural kinds in science are grounded in well-established causal structures, psychiatric classifications remain largely based on symptom clusters, with limited convergence on validated biomarkers or underlying mechanisms. The paper develops this claim along two lines. First, it highlights the lack of stable etiological grounding in psychiatry, where diagnostic categories often correspond to heterogeneous and overlapping causal pathways. Second, it emphasizes a conceptual difficulty: contemporary philosophy of science offers multiple competing accounts of natural kinds, each leading to different classificatory expectations. As a result, whether mental disorders qualify as natural kinds depends significantly on the theoretical framework one adopts. My conclusion is a moderate epistemic claim: mental disorders are real, and psychiatric classifications are indispensable, but their status as natural kinds is best understood as a revisable hypothesis rather than a settled assumption.