DEMENTIA VS. DEPRESSION
 Brooke J. Cannon, Ph.D.
 

DSM-IV DEFINITION OF DEMENTIA: "... the development of multiple cognitive deficits that include memory impairment and at least one of the following cognitive disturbances: aphasia,apraxia, agnosia, or a disturbance in executive functions. The cognitive impairment must be sufficuently severe to cause impairment in occupational or social functioning and must represent a decline from a previously higher level of functioning."

PREVALENCE: 2-4% of people >65 years old, increasing with age, with 20% in the >80-year-old group

DEMENTIA TYPES AND ASSOCIATED FEATURES: There are a variety of "dementias" which most frequently are categorized as "cortical" or subcortical." Alzheimerís disease is the most well-known example of a cortical dementia. Subcortical dementias include Parkinsonís, Huntingtonís, and AIDS dementia. The presentation of these two types of dementias differ:
 

CHARACTERISTIC CORTICAL SUBCORTICAL
Language aphasia early no aphasia
Memory recall/recognition impaired recall impaired; recognition normal or better preserved than recall
Visuospatial impaired impaired
Calculations impaired preserved until late
Frontal systems consistently impaired disproportionately affected
Speed of Cognition normal until late in course slowed early
Personality unconcerned apathetic, inert
Mood euthymic depressed
Speech normal articulation until late dysarthric
Posture upright bowed or extended
Coordination normal until late impaired
Adventitious movements absent (myoclonus occurs in some cases of Alzheimerís late in the course) present: chorea, tremor, tics, dystonia
Motor speed normal slowed
 

EMOTIONAL SEQUELAE OF STROKE (CVA): A variety of psychiatric symptoms have been associated with CVA, including:

affective syndromes dementia

apathy syndromes frontal lobe syndrome

anxiety syndromes indifference reaction

aprosody delusional disorders

catastrophic reaction personality change

delirium

LESION LOCATION AND DEPRESSION:

A study by Robinson et al. (1983) of stroke patients (all right-handed, no psychiatric history, and non-aphasic) found depression in 60% of patients with left anterior frontal lesions, compared to 18% of patients with left posterior lesions, 17% right posterior lesions, and 0% of thoses with right anterior frontal lesions.

This left-right hemisphere difference has also been found in subcortical infarctions, with left-sided more likely to result in depression.

CO-OCCURRENCE OF DEPRESSION AND DEMENTIA:

Alzheimerís disease - Depression likely to occur early in disorder, when patient first becomes aware of decreasing function. As the disorder progresses, insight becomes impaired, such that the patient no longer is aware of their deficits and depression is less likely to occur. Immediate, brief, catastrophic reactions may occur in reaction to negative events, but are not likely to persist.

Subcortical dementias - Depression tends to be part of the total symptom picture, with mood alteration not solely situational and more likely to be persistant. May respond to standard interventions. Depression likely to exacerbate cognitive deficits.

Multi-infarct/vascular dementia - Given correlation between left hemisphere infarcts and depression, as well as the greater frequency of left hemisphere CVAs, depression is very common after stroke, regardless of dementia. In cases of vascular dementia, there typically is a "patchy" presentation of deficits. Often insight is preserved, so that the patient is aware of their impairment. Thus, depression may result from lesion location and/or reaction to new limitations. Depression likely to exacerbate cognitive deficits.

 
PSEUDODEMENTIA
 
Term applied to apparent cognitive impairment associated with psychiatric disorders, most often depression (50-100%). Four criteria proposed by Caine (1981) for diagnosis:

1) intellectual impairment in a patient with a primary psychiatric disorder

2) features of impairment are similar to those seen in CNS disorders

3) the cognitive deficits are reversible

4) there is no known neurological condition to account for the presentation

 
PREVALENCE: Of patients referred for dementia evaluation, reports in the literature have ranged from 2% to 32% found to have a pseudodementia, with most reporting about 10%. There also is suggestion of overdiagnosis of degenerative dementia, with some studies reporting 20-50% of patients being misdiagnosed who really have a pseudodementia. Most cases occur in later life, with few reports in early or midlife.
 


Mental Disorders of Older Adults in Three Settings (from LaRue, 1992)

                                                    Relative frequency (%) of illness
 

Category of Illness
Community Residents
Medical Inpatients
Nursing-home residents
Cognitive impairment
4.9
30.2
84.0
Depressive disorders
2.5/8.0
18.5
8.0
Anxiety disorders
5.5
5.2
0
Alcoholism
0.9
2.6
0
Schizophrenia
0.1
0
0
Somatization
0,1
0
0
Personality disorders
0
8.3
0
Other disorders
0
7.9
2.0
 

PSEUDODEMENTIA FEATURES:


Major characteristics of the dementia syndrome of depression (all characteristics need not be present) (from Cummings and Benson, 1992)
 
Mental status changes Motor manifestations
  • dysphoria 
  • apathy
  • decreased motivation 
  • anxiety 
  • depressed affect
  • persecutory delusions 
  • psychomotor retardation 
  • impaired memory retrieval 
  • poor wordlist generation
  • dilapidation of cognition (calculation, abstraction) 
  • variable performance 
  • awareness of cognitive deficit
Neurovegetative signs  
  • sleep disturbance 
  • loss of appetite and weight 
  • constipation 
  • impotence
  • bradykinesia 
  • masked facies
  • stooped posture 
  • slow, hypophonic speech
History 
  • subacute onset and rapid progression of intellectual decline 
  • past history of mood disorder 
  • family history of mood disorder
Laboratory  
  • positive Dexamethasone test 
  • enlarged lateral ventricles
 
RESOURCES

    Cummings, J.L. & Benson, D.F. (1992). Dementia: A Clinical Approach. Boston: Butterworth-Heinemann.

Cummings, J.L., Ed. (1990). Subcortical Dementia. New York: Oxford University Press.

LaRue, A. (1992). Aging and Neuropsychological Assessment. New York: Plenum Press.

    Reichman, W.E. & Katz, P. (1996). Psychiatric Care in the Nursing Home. New York: Oxford University Press.

    Yesavage et al. (1983). Development and validation of a geriatric depression screening scale: A preliminary report. Journal of Psychiatric Research, 17, 37-49.
 
 



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