Generalized anxiety disorder and the Hamilton Anxiety Rating Scale in Parkinson's disease

Anxiety is common in Parkinson's disease (PD), but studies concerning specific anxiety disorders are scarce. Essential psychometric properties of anxiety rating scales are also lacking. Objective: To investigate general anxiety disorder (GAD) in PD and psychometric properties of the Hamilton Anxiety Rating Scale (Ham-A). Method: Ninety-one PD patients underwent neurological and psychiatric examination, which included the MINI-Plus, the Ham-A and the Hamilton Depression Rating Scale (Ham-D). Results: GAD was present in 30.8% of PD patients. Patients with GAD had longer disease duration (p=0.044) and were in use of higher doses of levodopa (p=0.034). They also tended to have more motor fluctuations and dyskinesias. The group with GAD scored higher in Ham-A (p<0.001), in the somatic (p=0.004) and psychic (p<0.001) subscales of Ham-A, and in Ham-D (p=0.004). The Ham-A showed good internal consistency (Cronbach's alpha=0.893) and a cutoff score of 10/11 is suggested to screen for GAD. Conclusion: GAD is frequent in PD and the Ham-A may be a useful instrument to screen for this disorder.