Low levels of cortisol are associated with which psychological disorder?

A) Type A personality
B) social phobia
C) post-traumatic stress syndrome
D) antisocial personality disorder

Low levels of cortisol have been associated with post-traumatic stress syndrome (PTSD), as research has shown that individuals with PTSD often have lower levels of cortisol, which is contrary to what might be expected given that cortisol is a stress hormone.