Background Depression and anxiety are common in Parkinson's disease (PD) and although clinically important remain poorly understood and managed. To date, research has tended to treat depression and anxiety as distinct phenomena. There is growing evidence for heterogeneity in PD in the motor and cognitive domains, with implications for pathophysiology and outcome. Similar heterogeneity may exist in the domain of depression and anxiety.

Objective To identify the main anxiety and depression related subtype(s) in PD and their associated demographic and clinical features.

Methods A sample of 513 patients with PD received a detailed assessment of depression and anxiety related symptomatology. Latent Class Analysis (LCA) was used to identify putative depression and anxiety related subtypes.

Results LCA identified four classes, two interpretable as ‘anxiety related’: one anxiety alone (22.0%) and the other anxiety coexisting with prominent depressive symptoms (8.6%). A third subtype (9%) showed a prominent depressive profile only without significant anxiety. The final class (60.4%) showed a low probability of prominent affective symptoms. The validity of the four classes was supported by distinct patterns of association with important demographic and clinical variables.

Conclusion Depression in PD may manifest in two clinical phenotypes, one ‘anxious–depressed’ and the other ‘depressed’. However, a further large proportion of patients can have relatively isolated anxiety. Further study of these putative phenotypes may identify important differences in pathophysiology and other aetiologically important factors and focus research on developing more targeted and effective treatment.