s.u.

Wörterbuch der deutschen Sprache:
dys|funk|ti|o|nal [Adj. ; Med.] in einer Funktion gestört

Encarta:
dys·func·tion·al [ diss fúngkshən'l ]
adjective
Definitions:
1. relating badly: characterized by an inability to function emotionally or as a social unit
a dysfunctional family
dysfunctional behavior
2. not performing as expected: failing to perform an expected function
a dysfunctional bureaucracy
3. affected by disease or impairment: describes an organ or other part or system of the body that is unable to function regularly as a result of disease or impairment
 
Cambridge Advanced Learner's Dictionary:
Definition
dysfunction [Show phonetics]
noun [C] SPECIALIZED
a problem or fault in a part of the body or a machine:

There appears to be a dysfunction in the patient's respiratory system.
dysfunctional [Show phonetics]
adjective SPECIALIZED
not behaving or working normally:
a dysfunctional family


Früheren Diskussionen zur Folge wird der Begriff im Deutschen auch in der Soziologie verwendet:
  related discussion:d/dysfunctional.html
An hinreichenden Nachweisen mangelt es hier aber bislang.