Difference. Catatonia refers to a state of schizophrenia where the patient doesn't move, appears like a statue, and has no emotional expression on their face. Emotionally unavailable can refer to a preoccupied person, a person whose emotions are effectively in deep freeze of sorts due to trauma, or a person who has schizoid personality disorder the hallmark of which is indifference to relationships.
A LOT! Catatonia is a sign of severe mental illness. Patients with catatonia are not thinking clearly. Sometimes they take minutes to answer a simple question. Sometimes their answer does not correspond to the question. They often have odd movements or will not move for long periods of time.
A big difference. Catatonia is an uncommon, severe and life threatening psychiatric condition. Usually in the context of severe mood disorders. It involves inability to speak, marked reduction in physical movement, not eating or drinking. Emotional unavailability is a pop sort of term for someone who is not terribly communicative, doesn't want to interact with others, perhaps avoids emotional attachments. Read more...