In mental health conversations, you’ll often hear conditions like depression, anxiety, or schizophrenia referred to as disorders rather than diseases. This distinction is not random but it reflects how psychology and psychiatry understand human behavior, emotions, and brain functioning.
In medicine, a disease is typically linked to a clear biological cause. For example:
Diseases can usually be detected through lab tests or scans, and they often have a fairly predictable progression and treatment.
Most mental health conditions don’t neatly fit into the “disease” category because:
That’s why the term “disorder” is used — it literally means a disruption of normal order or functioning. In psychology, it indicates that something in thought, emotion, or behavior has become dysregulated.
None of these have a single biological test that can “prove” them, which is why we don’t label them as diseases. Instead, diagnosis relies on structured assessments, clinical interviews, and standardized criteria (like those in the DSM-5 or ICD-11).
In psychology, we call it a disorder because mental health struggles are not simply about one biological defect or germ. They’re about disruptions in the complex system of mind, brain, and environment.