Many depressive symptoms are seen in the normal course of Parkinson’s disease (PD). As a result, depression—the most common neuropsychiatric disturbance in PD—is difficult to assess in PD and easily can go undetected and untreated.

Making the diagnosis is important, however, because depression causes PD patients suffering and may accelerate decline in motor and cognitive function, activities of daily living, and quality of life. In the absence of specific guidelines, we provide evidence to help you sort through the overlapping symptoms to find clinical signs that differentiate depression from PD symptoms.

Symptoms of depression that occur in or mimic those in the natural course of PD

Psychomotor retardation (bradykinesia)
Depressed or emotionless appearance (‘masked facies,’ stooped posture)
Agitation (dyskinesias)
Decreased interest and enjoyment (apathy and decreased initiative)
Impaired memory and concentration
Fatigue or decreased energy
Impaired sleep
Weight and appetite changes
Physical complaints

Frequency of depressive symptoms in Parkinson’s disease

Effect
Significantly higher frequency in PD patients with depression
Symptoms
Worrying, brooding, loss of interest, hopelessness, suicidal tendencies, social withdrawal, self-depreciation, ideas of reference, anxiety symptoms, loss of appetite, initial and middle insomnia, loss of libido

Effect
No significant differences in frequency compared with PD patients without depression
Symptoms
Anergia, motor retardation, early morning awakening

Recommendations
As we have seen, depression’s somatic and cognitive symptoms and PD’s motor, somatic, and cognitive features overlap substantially. How, then, should clinicians handle symptoms that can be attributed to either depression or PD? Several approaches are possible and each has strengths and weaknesses.

An exclusionary approach may be indicated for research, whereas an inclusive approach may be better suited to clinical settings. As mentioned, the National Institute of Neurological Disorders and Stroke/National Institute of Mental Health Work Group on Depression in Parkinson’s Disease supports an inclusive approach when evaluating depression symptoms. This group also recommends eliminating the DSM-IV-TR general exclusion criterion “due to the effects of a medical condition” applied to the diagnosis of depression.

As we have seen, however, most DSM-IV-TR depressive symptoms overlap with PD symptoms. The false-positive results likely to occur with an inclusive definition of depression might discourage clinicians from screening PD patients for depression.

In clinical practice, finding recent changes in these overlapping symptoms might point to depression. Therefore, try to establish recent changes—associated with depression—in a PD patient’s somatic or cognitive symptoms, such as weight loss, lack of interest, impaired concentration, or decreased energy. This may be difficult, however, given:

  * the subjective nature of many of these symptoms
  * the decreased reporting ability of patients with cognitive deterioration
  * medical comorbidities in PD that also could produce the referred symptoms.

For these reasons, in clinical practice perhaps the best way to detect depression in PD is by giving primacy to mood symptoms, with the option of using cognitive and somatic DSM-IV-TR symptoms when reliable and clear information is available. Some changes in the approach to specific depressive symptoms in PD also are probably worth considering:

1. Mood. Try to differentiate pervasive depressed mood from mood fluctuations associated with motor fluctuations and poorly controlled motor symptoms. Start with simple, open-ended questions and progress toward precise estimates.

Ask the patient about how often he or she feels sad or “down” and if these feelings are related to something specific or PD symptoms such as “freezing.” Depression rating scales such as the HAM-D and Geriatric Depression Rating scale, though useful for mass screening or research, have very limited clinical application.

2. Interest. Depressive loss of interest may be more acute and fluctuating than apathy. Also, selective loss of interest in some areas—such as social life, work, or hobbies—as opposed to the pervasive character of apathy, may suggest depression.

When evaluating interest in PD patients, consider that they may be avoiding activities that interest them out of fear that motor impairment may cause poor performance or social embarrassment.

3. Weight/appetite. Appetite may be a better indicator of depression than weight changes, as weight loss seems to be common in PD patients. Keep in mind, however, that the GI side effects of dopaminergic medications may limit what patients can eat.

4. Insomnia/hypersomnia. Insomnia associated with PD is usually characterized by sleep maintenance problems (middle insomnia or “broken” sleep). Thus, initial and terminal insomnia are probably better indicators of the presence of depression.

5. Agitation/retardation. Psychomotor retardation is common in PD, but acute exacerbations associated with depression may be noticed. Also note that depression-associated anxiety may exacerbate dyskinesias.

6. Fatigue or loss of energy is a very difficult symptom to ascribe either to PD or depression unless they change acutely.

7. Worthlessness/guilt. PD is an incapacitating illness that causes work, family, and social dysfunction. To count as a depression criterion, worthlessness and guilty feelings need to be excessive or inappropriate and relatively constant and not merely self-reproach or guilt about being sick.

8. Diminished ability to think and concentrate is another a symptom that is difficult to ascribe to either depression or PD. A recent change in the context of mood symptoms might point to depression.

9. Recurrent thoughts of death. As mentioned, suicide seems to be less common in patients with PD than in the general population, but suicidal ideation—when found—is highly specific. Fear of dying from PD is not considered a depressive criterion, however.

PD: Parkinson’s disease

 

Humberto Marin, MD
Assistant professor

Matthew Menza, MD
Professor and vice chair

Roseanne Dobkin, PhD
Assistant professor

Department of psychiatry, Robert Wood Johnson Medical School, Piscataway, NJ
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