Markers for depression in Parkinson's disease

Objective: To assess whether general risk factors for depression are also markers of depression in patients with Parkinson's disease (PD) and to identify additional disease-specific markers. Method: A two-step logistic regression was performed on data from 161 consecutively referred PD patients, 40 of whom suffered from major depressive disorder. A first logistic model was created with five general risk factors for depression. Next, five potential disease-specific markers were added to see whether this would improve the model. Results: The logistic model of general risk factors for depression also predicted depression in PD patients. A family history of depression was the most important marker. `Right-sided onset' was the only disease-specific marker that improved the model. Conclusion: Established risk factors for depression in the general population are also markers of depression in PD. The importance of correcting for general risk factors for depression in the search for disease-specific risk factors is stressed.