Affective Correlates of Psychosis in Parkinson's Disease

Abstract

Background: In Parkinson's disease (PD), psychosis and affective disorders are common and independently impact quality of life and mortality. Both depression and psychosis are correlated with the occurrence of cognitive dysfunction, suggesting that they may share neurobiological substrates. Anxiety has not been examined as a correlate of psychosis. The objective of this study was to examine the nature of the association between affective disorders and psychosis in patients with PD. Methods: One hundred forty-four patients with PD were evaluated using the Schedule for Assessment of Positive Symptoms to assess psychotic features, while depression and anxiety were examined using the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (SCID) and 2 self-assessment scales: the Beck Depression Inventory II and the Beck Anxiety Inventory (BAI). Correlational analyses assessed associations between hallucinations and delusions with depression and anxiety. Results: A diagnosis of anxiety (SCID) was significantly associated (P = 0.015) with hallucinations (odds ratio [OR], 4.81; 95% confidence interval [CI], 1.36–16.99). The severity of anxiety (Beck Anxiety Inventory) significantly predicted (P = 0.03) the presence of hallucinations (OR, 1.08; 95% CI, 1.01–1.15) and delusions (OR, 1.09, confidence region, 1.01–1.17). Current depression (SCID) was significantly associated (P = 0.001) with the presence of hallucinations (OR, 6.12; 95% CI, 2.04–18.39) and delusions (OR, 7.14; 95% CI, 2.23–22.93). Multiple linear regressions revealed that severity of anxiety remained an independent predictor (P < 0.05) of both the number of types of hallucinations (t = 3.06; P = 0.003) and delusions (t = 2.87; P = 0.005). Severity of depression was a significant predictor of the total number of delusions (t = 2.28; P = 0.024). Conclusions: This study demonstrates an association between depression and psychosis and, for the first time, an association between anxiety and psychosis. These associations may have implications for the pathophysiology and treatment of psychosis in patients with PD.