Parkinson’s symptoms or depression? Look for clinical signs

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.

Table 3

4 options for diagnosing depression in PD patients

Approach	Definition	Comment
Inclusive	Count all depressive symptoms toward a depression diagnosis	Recommended by NINDS/NIMH Work Group on Depression in Parkinson’s Disease, but may result in overdiagnosis of depression in PD patients
Exclusive	Ignore any depressive symptoms that could otherwise be explained	May be indicated for research
Etiologic exclusive	Ignore symptoms that likely are the result of the medical illness	The NINDS/NIMH Work Group on Depression in Parkinson’s Disease recommends avoiding attributing symptoms to a particular cause
Substitutive	Replace the most confusing diagnostic features with others that are less controversial	Theoretically the best approach, but establishing this approach as evidence-based would require substantial research
PD: Parkinson’s disease; NINDS/NIMH: National Institute of Neurological Disorders and Stroke/National Institute of Mental Health
Source: References 4,33

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.

Related resources

• Menza M, Marsh L, eds. Psychiatric issues in Parkinson’s disease: a practical guide. New York: Taylor and Francis; 2006.
  
• Marsh L, McDonald WM, Cummings J, et al. Provisional diagnostic criteria for depression in Parkinson’s disease: report of an NINDS/NIMH work group. Mov Disord 2006;21:148-58.
  
• Parkinson’s Disease Foundation: www.pdf.org.
  
• Michael J. Fox Foundation: www.michaeljfox.org.