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Diagnosis of Depression in Parkinson's Disease

Diagnosis of Depression in Parkinson's Disease

Bernard Ravina, MD, Emmeline Edwards, Ph.D., & Paul Sheehy, Ph.D. NINDS
Hotel Sofitel, Washington DC, December 4-5, 2003

A conference to address diagnostic issues related to depression in PD was held on December 4 and 5, 2003 in Washington DC. The conference, was sponsored by the National Institute of Neurological Diseases and Stroke (NINDS) with participation from the National Institute of Mental Health (NIMH), and was organized and moderated by Dr. Bernard Ravina of NINDS. One of the goals of the conference was to determine whether or not current diagnostic criteria for depression, as outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth addition (DSM-IV), are adequate to effectively diagnose depression in PD. Another goal was to determine if currently available depression rating scales are adequate for use in PD. A fundamental question that was debated is whether or not depression in PD is different than depression in non-PD patients. The conference did not yield definitive answers, but resolved some issues and framed the approach necessary to advance our knowledge of depression in PD and, ultimately, to alleviate suffering in affected patients and their loved ones. The participants in the meeting included psychiatrists, psychologists, neurologists and a statistician, who all brought vast and diverse experience to the table. There were formal presentations and lively discussions. The presentations included overviews of the clinical characteristics, causes and classification/measurement of depression in PD. Several participants reviewed research studies in which currently available diagnostic criteria and depression rating scales were used in PD populations.

An Overview of Depression in Parkinson's Disease

Studies indicate that almost half of all PD patients will experience depression at some point in their illness. Depression is different from normal sadness that everyone experiences on occasion. Depression is an illness characterized by sad mood and/or diminished ability to enjoy things accompanied by other symptoms such as changes in appetite, problems sleeping or excessive sleepiness, decreased energy level, slowed movements and poor concentration. At times, patients can have recurrent thoughts of death or that life is not worth living. Depression is generally diagnosed when these symptoms have been present every day for at least two weeks. It has been shown that depression in PD is a leading factor contributing to reduced quality of life (more so than the motor features). Most research suggests that depression in PD is caused by biological changes related to the underlying brain disease, rather than solely a reaction to disability.

Difficulties Associated with Diagnosing Depression in PD

It can sometimes be difficult to make a diagnosis of depression in the setting of PD. This is, in part, because many symptoms of depression (e.g. slowed movements, sleep disturbances) may also be seen in non-depressed PD patients. It is also not clear how closely depression in PD resembles depression seen in non-PD patients. Furthermore, there are some aspects of PD that must be kept in mind when attempting to evaluate depression in PD. For example, many patients with PD who have fluctuations in their motor function also have fluctuations in their mood. These individuals may look and act very differently depending on their motor and mood state.

The reasons for ensuring diagnostic accuracy include the following:

  • To make sure that we are capturing all depressed PD patients with our current criteria so that they be diagnosed and treated.
  • PD patients may have "atypical" features to their depression (such as more anxiety or less guilt than depressed people without PD)
  • Many PD patients have less severe (but none-the-less distressing) symptoms and they would not meet current criteria for the diagnosis of a depressive syndrome These patients are sometimes referred to as having "subsyndromal" depression.
  • To make sure that we are not diagnosing depression based on symptoms that, while part of the current depression criteria are not due to depression in those particular patients. Symptoms that can be seen in both depressed and non-depressed PD patients include sleep disturbance, apathy, diminished concentration and slowed thinking and movements.

Some participants suggested excluding these symptoms from the current diagnostic criteria but others argued that modifying the criteria would be premature because we lack evidence on which to base any change in existing criteria. For example, we really don't know for sure that PD patients with depression are any more anxious than other patients who are the same age, nor do we know if (and to what extent) symptoms such as sleep disturbance and diminished concentration are part of the depressive syndrome in PD.

Depression Rating Scales

Another goal of the meeting was determine whether or not current depression rating scales are adequate in this population. Rating scales can either be self-administered (e.g. Beck Depression Inventory) or administered by an examiner in the form of an interview (Hamilton Depression Rating Scale). Rating scales are not used to diagnose depression. Their uses include the following:

  • to screen people for the presence of depression (patients obtaining a certain score or higher are then interviewed to determine whether or not they have depression), 
  • to measure the severity of depression in patients who have already been diagnosed, 
  • to measure what effects treatments for depression are having on the symptoms of the illness. 

Several participants reviewed the use of various depressions rating scales in PD and provided some fairly compelling evidence that, the existing scales are both valid (are measuring what they are supposed to measure) and reliable (measure the same thing each time they are used). It was the consensus of the group that the examiner should count every symptom, rather than try to determine whether or not a symptom is due to depression or due to some other aspect of PD. For example, patients with problems sleeping would get points on the rating scales for sleep disturbances, regardless of whether their insomnia was perceived to be due to worrying or tremor.

Treatment of Depression in PD

The meeting did not address treatment of depression in PD but the group agreed that we need to 1) increase awareness of depression in PD and 2) determine the best way to treat PD patients with depression. Despite the large number of PD patients suffering from depression, there have been no rigorous studies of antidepressant medications in this disease. Fortunately, one clinical trial is underway and another multicenter clinical trial is planned to start in April 2004.

Source: National Institute of Neurological Disorders and Stroke

Last updated November 05, 2004

Last reviewed by on February 3, 2014