Classified as a “conversion disorder” by the DSM-IV, a<unk>  is a disease in which mental stressors cause physical symptoms of different diseases. The manifestation of physical symptoms without biologically identifiable causes results from disruptions of processes in the brain from psychological stress. During a<unk> , neuroimaging has shown that neural circuits affecting functions such as emotion, executive functioning, perception, movement, and volition are inhibited. These disruptions become strong enough to prevent the brain from voluntarily allowing certain actions (e.g. moving a limb). When the brain is unable to signal to the body to voluntarily perform an action, physical symptoms of a disease are presented even though there is no biological identifiable cause. Examples of diseases that are believed by many to be<unk>  include<unk>  seizures,<unk>  polydipsia,<unk>  tremor, and<unk>  pain. The term<unk>  is often used in a similar way to psychosomatic disease. However, the term<unk>  usually implies that psychological factors played a key causal role in the development of the illness. The term psychosomatic is often used in a broader way to describe illnesses with a known medical cause where psychological factors may nonetheless play a role (e.g., asthma can be exacerbated by anxiety).
Psychogenic disease
Neurodegenerative disease
Vitamin deficiency
Viral disease
Metabolic disorder
Diathesis 
Degenerative disease
Parasitic disease