BACKGROUND The study tested the hypothesis that subjects with Parkinson's disease (PD) have more autonomic complaints and more attenuation of autonomic reflexes than controls, and that both clusters of variables are related to the presence of anxiety and depression.
METHOD Thirty-two subjects and 32 healthy controls matched by age and sex were prospectively compared on psychiatric, cognitive and autonomic tests.
RESULTS 'Autonomic' symptoms: were more frequent in PD patients than in healthy controls; were not related to age or changes in autonomic reflexes; were significantly associated with depression and anxiety (medication was not relevant to the association); and did not correlate with motor symptoms.
CONCLUSIONS The diagnosis of anxiety and depression in some PD subjects is likely to be a behavioural phenocopy caused by autonomic failure. This explains why antidepressant medication is often unhelpful in PD subjects diagnosed as depressed.