What type of disorder is characterized by no known brain injury?

The correct answer is functional disorder. Functional disorders are characterized by symptoms that occur without a clear biological or physical cause, such as a brain injury or a specific lesion. In these cases, individuals may experience various psychological or behavioral symptoms, but traditional medical imaging techniques, like MRI or CT scans, do not reveal any structural abnormalities in the brain.

In the context of behavioral health, functional disorders often include conditions like anxiety disorders, depression, and some personality disorders. These syndromes highlight how mental health issues can arise from complex interactions of psychological, social, and environmental factors rather than direct physical damage to the brain. This differentiates them from organic disorders, which are directly linked to identifiable physical changes or injuries in the brain.

The other types of disorders listed—psychotic, organic, and mood disorders—either imply specific brain conditions, underlying physical causes, or are associated with clear psychiatric diagnoses that may not fit within the functional framework. Thus, functional disorders accurately capture the essence of having no known brain injury while still presenting significant psychological distress.