Final answer:
Conversion disorder is the psychological disorder where psychological distress is expressed through physical symptoms with no identifiable physical causes.
Step-by-step explanation:
The major psychological disorder in which psychological symptoms manifest in physical form without any physical cause is known as Conversion disorder. This condition falls under the broader category of psychophysiological disorders, wherein physical symptoms have a psychological component. Conversion disorder is characterized by neurological symptoms like paralysis, blindness, or other sensory and motor deficits that cannot be explained by medical evaluation and do not align with medical conditions.