Parkinson's disease with depression: a possible subgroup of idiopathic parkinsonism.

We investigated the prevalence of mental depression (MD) in 34 patients with Parkinson's disease (PD) of recent onset, not receiving dopaminergic drugs, and in 23 healthy individuals of comparable age and sex. In the patients, dysthymic disorder and major depression were more common than in controls (p = 0.017). The severity of MD and PD were unrelated. In 15 patients, MD began before the symptoms of PD (mean, 5 years). These patients were younger, less impaired, and with a higher positive family history of PD. MD-associated PD may be a specific subgroup of PD.