Parkinson’s symptoms or depression? Look for clinical signs

Current Psychiatry. 2007 July;06(07):78-87

July 1, 2007|Current Psychiatry

How to sort through overlapping symptoms using DSM-IV-TR diagnostic criteria.

Clinical Point

Up to one-half of PD patients report fatigue, and many consider it more disabling than their motor symptoms

7 Feeling worthless/excessive or inappropriate guilt. DSM-IV-TR defines this symptom as not merely self-reproach or guilt about being sick.⁶ Guilt or self-blame seem to be less common in PD depression compared with dysphoria, pessimism, and somatic symptoms.²² Nonetheless, feelings of decreased self-worth are common in PD patients, especially as the illness limits work, productivity at home, and social activities.

8 Concentration and decision-making. PD patients show cognitive changes such as difficulty in changing tasks and impaired executive function (planning, sequencing, and executing). In tasks of divided attention—such as “multitasking”—PD patients have difficulty filtering out nonrelevant information.²³ Difficulties with memory, attention, and language also have been observed in PD and often are exacerbated by depression.²⁴ These cognitive changes affect PD patients’ ability to concentrate, maintain focus, and engage in effective decision making.²⁵

Attention problems in PD are compounded by dementia, which affects at least 20% to 40% of PD patients²⁶ and perhaps considerably more.²⁷

Box

Count all depressive symptoms?

To study depression in PD patients, the NINDS/NIMH Work Group on Depression in Parkinson’s Disease⁴ recommended that researchers use DSM-IV-TR criteria for depression and count all overlapping depressive symptoms toward a depression diagnosis.

Unfortunately, this provisional recommendation—intended only to “provide a common starting point for clinical research in PD-associated depression”⁴—is not evidence-based, and its specificity and sensitivity are unknown. If you follow this recommendation in clinical practice, you might overdiagnose depression in PD patients by including false positives and nonsignificant cases.

Until these issues are clarified, we recommend that you focus on the most specific symptoms, such as mood, when assessing depression in PD patients.

9 Suicide in PD. Recurrent thoughts of death, suicidal ideation, a suicide attempt, or a specific plan for committing suicide are included in DSM-IV-TR criteria for depression.⁶ Thoughts of death also may be a common symptom in PD, although a large American study found that individuals with PD—despite their extremely high rates of depression—had a significantly lower risk of suicide than age-matched controls without PD.²⁸

Features of depression in PD

The specificity and clinical usefulness of individual depression symptoms in PD is variable. Some symptoms seem to be as common in nondepressed as in depressed PD patients (Table 2).²⁹

Distinguishing characteristics. Using Hamilton Depression Rating Scale (HAM-D) and Montgomery-Åsburg Depression Rating Scale items, a study of nondemented PD patients found the presence of suicidal thoughts to be the most reliable discriminator between depressed and nondepressed patients. Other symptoms with good discriminating reliability for depression in PD were (in descending order):

feelings of guilt
psychic anxiety
reduced appetite
depressed mood
reduction of work and interest.

Somatic items—such as fatigue, somatic anxiety, weight loss, and early and middle insomnia—had the lowest discriminative properties.³⁰

Clinical Point

Fatigue, anxiety, weight loss, and insomnia are least reliable in discriminating depressed vs nondepressed PD

Symptom profile. The most recent studies comparing depression symptoms in PD patients with those in non-PD populations seem to indicate:

the profile of depression in PD is not different from that of other elderly depressed populations
or PD patients show more cognitive symptoms, which is not surprising considering PD’s cognitive involvement.³¹

Keep in mind that if the same definition of depression is used in 2 different populations, the symptomatic profiles are likely to be the same.

Psychiatric comorbidities. A relatively high association with anxiety, cognitive impairment, and psychosis also complicates depression’s picture in PD.³² Often this relationship seems to be bidirectional, with the comorbidities increasing the risk for depression and vice versa.

Table 2

Frequency of depressive symptoms in PD

Effect	Symptoms
Significantly higher frequency in PD patients with depression	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
No significant differences in frequency compared with PD patients without depression	Anergia, motor retardation, early morning awakening
PD: Parkinson’s disease
Source: Reference 29

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 (Table 3),³³ 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 Disease⁴ supports an inclusive approach when evaluating depression symptoms. This group (Box) also recommends eliminating the DSM-IV-TR general exclusion criterion “due to the effects of a medical condition” applied to the diagnosis of depression.⁴

References