Anxiety in Parkinson's Disease: Diagnostic Evaluation and Pitfalls

Abstract & Commentary

By Melissa J. Nirenberg, MD, PhD, Assistant Professor, Neurology and Neuroscience, Weill Cornell Medical College. Dr. Nirenberg has consulted for Biovail and participated in clinical trials sponsored by Boehringer-Ingelheim.

Synopsis: Anxiety is a common but underrecognized symptom of Parkinson's disease, for which there are a number of suggested but no recommended rating scales.

Source: Leentjens AF, et al. Anxiety rating scales in Parkinson's disease: Critique and recommendations. Mov Disord 2008;23:2015-2025.

The evaluation and treatment of parkinson's disease (PD) is mainly focused on the well-recognized motor features of the disease, such as rest tremor, rigidity, and bradykinesia. In recent years, however, there has been increasing recognition of the high prevalence and major clinical impact of the non-motor symptoms of PD. Anxiety is one of the most common and treatable of these non-motor symptoms, and yet one about which there has been surprisingly little clinical research.

One of the major impediments to the study of anxiety in PD has been the lack of recommended PD anxiety rating scales. To address this problem, a task force was commissioned by the Movement Disorder Society to systematically evaluate the clinimetric properties of anxiety rating scales that had been previously validated or used in peer-reviewed publications about PD. Based on a literature search, the authors identified and evaluated 6 of these scales. These included the Beck anxiety inventory (BAI), hospital anxiety and depression scale (HADS), Zung self-rating anxiety scale (SAS) and anxiety status inventory (ASI), Spielberger state trait anxiety inventory (STAI), and Hamilton anxiety rating scale (HARS). They also examined item 5 (anxiety) on the neuropsychiatric inventory (NPI) because of the frequency with which it has been used in PD; other multidimensional scales were excluded. Each rating scale was critically reviewed by two task force members. Rating scales were then classified as "recommended" (used in PD beyond the original developers, with successful clinimetric testing), "suggested" (used in PD beyond the original developers or used in PD with successful clinimetric testing in this population), or "listed" (used in PD only by the original developers, with no successful clinimetric testing in PD).

A brief summary of their findings was presented in the printed version of the journal article, with greater detail presented in the accompanying on-line version. The BAI was "suggested" as a screening test for episodic anxiety disorders (such as panic attacks), for studying the epidemiology and biomarkers of anxiety symptoms, and for evaluating responses to changes in treatment. The HADS had limited clinimetric information, and was therefore "suggested" for use in screening for anxiety, but not for studying the phenomenology of anxiety disorders in PD. The Zung SAS had been used in epidemiological studies in PD, but not validated in this population, and the ASI has only been used in one study in PD; neither has been used in PD treatment studies. These studies were therefore also classified as "suggested" for use in PD. The STAI has not been validated in PD, but was found to be particularly useful for evaluating sustained anxiety disorders such as generalized anxiety disorder, and was "suggested" for use in screening for anxiety, studying anxiety biomarkers, and as an outcome measure in PD. The HARS has not been validated in PD, nor is there any information about its clinimetric properties in PD, but it has been used in studies of the epidemiology and symptomatology of anxiety in PD patients and, therefore, met criteria as "suggested" for use in PD. The NPI anxiety subscale also had almost no data about its clinimetric properties in PD, but was "suggested" for use in PD, and may be most useful as a screening tool for anxiety, or for estimating the severity of anxiety in patients with dementia.

In the final analysis, the task force classified all of the above anxiety rating scales as "suggested" and none of them as "recommended" for use in PD. This was because none of the rating scales had undergone successful clinimetric testing and in PD. The task force concluded that further study was needed before any of these rating scales could be specifically recommended for use in PD, and that if none of these scales prove to be acceptable, then it may be necessary to devise a new PD-specific anxiety rating scale.

Commentary

Anxiety has been associated with reduced quality of life and greater subjective motor symptoms in PD, and with increased caregiver burden and health care utilization in the general population. Yet remarkably little is known about the prevalence, prognosis, and treatment in PD. Rating scales that accurately identify and quantify the severity of anxiety in PD are needed to support clinical research about the prevalence and optimal treatments of anxiety in PD, and to facilitate accurate clinical diagnosis in the setting of routine patient care.

The clinical presentation of anxiety in PD appears to differ from that in the general population, such that standard anxiety rating scales—and even the "gold standard" DSM-IV criteria—may misclassify patients. Anxiety symptoms (such as shakiness, restlessness, and dizziness) may have considerable overlap with symptoms of depression, motor features of PD (such as tremor and akathisia), and other non-motor PD symptoms (such as dizziness due to orthostatic hypotension). PD patients may also experience fluctuations in anxiety related to medication timing ("non-motor offs"), and medication-induced impulse-control disorders. These unique properties of anxiety in PD underscore the importance of identifying rating scales that appropriately identify and measure the severity of anxiety in PD.

This report supports the use of a number of different rating scales that can be used in PD, provides useful information about the strengths and weaknesses of the various tests that are available, and highlights the need for further study before any specific scale can be classified as "recommended." More importantly, the report calls attention to the need for greater research about this common, debilitating, and treatable non-motor manifestation of PD.