Anxiety and Depression Are Often Comorbid with Psychosis in Parkinson's Disease

Study results indicate a significant correlation between depression and hallucination in patients with Parkinson's disease, while anxiety is a significant predictor for both the number and severity of hallucinations.

At the 2013 Annual Meeting of American Neurological Association, Stewart Factor, MD, presented findings on the prevalence of anxiety and depression as comorbidities of psychosis in Parkinson’s disease (PD). Factor is a professor of neurology at the Emory University School of Medicine in Atlanta.

Hallucinations and delusion are quite common in Parkinson’s disease, occurring in about 60 percent of patients through the course of their disease. These are often chronic symptoms that carry increased risk for mortality. Depression and anxiety are also common comorbidities in Parkinson’s, occurring in about 40 percent of patients with the disease. As with psychosis, these disorders impact quality of life, mortality, and cognitive function. “There is a lot of literature that shows that anxiety and depression are undertreated in Parkinson’s disease,” Factor noted.

Factor and colleagues sought to examine the association of these symptoms in PD. They collected in-depth measurements of symptoms by using the Scale for the Assessment of Positive Symptoms (SAPS), which assesses hallucination and delusion severity as part of a patient interview.

Measurements of anxiety and depression included the Structured Clinical Interview for DSM-IV (SCID). The Beck Anxiety and Depression Inventory also allowed the researchers to assess symptom severity. Patients were evaluated in a standardized fashion over a five-hour period.

The present study included 144 participants with PD. The subjects had an average age of 64.7 years, an average age of disease onset of 59.5 years, an average Unified Parkinson’s Disease Rating Scale score of 17.7, and an average mini-mental state examination score of 28.3.

Twenty-six percent of participants reported hallucinations, 16 percent reported delusions, and 8 percent reported both. A diagnosis of depression significantly correlated with the presence of hallucinations (after controlling for potential confounders). There was also an associational trend between depression and delusions (p = 0.08). Increased severity of depression and anxiety also correlated with the severity of hallucinations.

Using linear regressions, the researchers also showed that anxiety (but not depression) was a significant predictor for both the number and severity of hallucinations. Increased anxiety and depression were also significantly correlated with an increase in the types of delusions.

“We found the association of depression with psychosis was more driven by anxiety than by depression, which no one had reported before,” Factor explained. “In my practice, patients with psychosis are all highly anxious people.”

These study findings confirm the association of psychosis with depression and anxiety in PD. It is crucial for clinicians to identify and treat these very common co-morbidities. The researchers suggest that a longitudinal study is needed to determine whether mood disorders are risk factors for the development of psychosis in PD or whether the mood disorders might be byproducts of the psychosis.

“Psychosis is very difficult to control,” Factor concluded. “Perhaps using anti-anxiety medication in people with psychosis might make an impact.”

The Consolidated Anti-Aging Foundation supported this study.