Mohammed T. Abou-Saleh

Principles and Practice of Geriatric Psychiatry.Editors: Professor John R. M. Copeland, Dr Mohammed T. Abou-Saleh and Professor Dan G. BlazerCopyright & 2002 John Wiley & Sons LtdPrint ISBN 0-471-98197-4 Online ISBN 0-470-84641-055aDistinguishing Depression from DementiaWilliam E. Fox and David C. SteffensDuke University Medical Center, Durham, NC, USARecent research continues to confirm the complex relationshipbetween depression and dementia. The ability to distinguishdepression from dementia is complicated by the overlap of manyof their clinical manifestations. Differentiating the two illnesses isfurther complicated in that depression and dementia are oftenconcurrent illnesses in the geriatric population. Depression hasalso become recognized as a possible prodrome, or even riskfactor, for degenerative dementias. Finally, cerebrovasculardisease, one of the long-established etiologies of dementia, isbecoming increasingly recognized as a possible etiology ofgeriatric depression.Dementia and depression are two of the most commondiagnoses that clinicians encounter in geriatric psychiatry. Theprevalence of dementia has been estimated to be approximately1% at age 60, doubling every 5 years to reach 30% to 50% by age85 1,2 . Major depression afflicts 1–2% of community-dwellingelderly, with significantly higher rates observed in hospitalizedelderly and those residing in nursing homes 3 . The prevalence forminor depression or subsyndromal depression is even higher, withrates reported to be 13–27% 3 .Given the complex relationship between depression anddementia, combined with high prevalence rates, clinicians needto be familiar with the literature that addresses these issues. Thischapter will begin with a review of the basic diagnostic criteria ofdementia and depression. It will then explore the key points inclinically distinguishing the diagnoses. Next, it will examine theissue of concurrent depression and dementia, as well as theconcept of pseudodementia of depression. It will conclude with adiscussion regarding the latest research on the possibility ofdepression as a herald or prodrome of degenerative dementias,and the newly emerging concept of vascular depression.CLINICAL PRESENTATIONS OF DEMENTIA ANDGERIATRIC DEPRESSIONThe DSM-IV diagnostic criteria for dementia include thedevelopment of multiple cognitive deficits manifested by memoryimpairment, and one or more of the following: aphasia, apraxia,agnosia or disturbance in executive functioning 4 . In addition tothese core cognitive symptoms, numerous psychiatric symptomsare also common. In Alzheimer’s disease (AD), the most commonof the dementing disorders 5 , significant psychiatric symptomsoften occur, including personality changes, irritability, anxiety,delusions, hallucinations and depressive symptoms 5–8 . The depressivesymptoms that are common in dementia include sleepdisturbance, anorexia, irritability, social withdrawal, anergy andapathy 6,7 .The diagnostic criteria for major depressive disorder, asdescribed in the DSM-IV, include depressed mood, diminishedinterest, weight loss, sleep disturbance, psychomotor agitation orretardation, loss of energy, feelings of worthlessness or guilt, anddiminished ability to concentrate 4 . While not all studies agree,most authors report that in the elderly, compared to youngerdepressive counterparts, depressed mood and feelings of guilt arenot as common but somatic and cognitive symptoms are morecommon 3,9 . The cognitive symptoms may become so severe as tolead to the development of what has been termed ‘‘pseudodementia’’.With such significant overlap of the symptoms of dementia anddepression in the elderly, the clinical or ‘‘bedside’’ differentiationcan be quite challenging. Reynolds et al. 10 found that patientswith pseudodementia of depression showed greater early morningawakening, higher anxiety and more severe impairment of libido.Patients with dementia showed more disorientation to time andgreater difficulty with dressing and navigating through familiarsurroundings.The American Association for Geriatric Psychiatry, theAlzheimer’s Association and the American Geriatric Societypresented a consensus statement that included tips for differentiatingdementia from depression 5 . The panel reported thatpatients with AD, in comparison with depressed patients, tend tominimize cognitive deficits, demonstrate impaired memory andexecutive function, have ‘‘indirect’’ symptoms of depression, suchas agitation and insomnia, and demonstrate other cognitivedeficits, such as aphasia and apraxia. The panel further reportedthat those patients with cognitive disturbance, in the context ofdepression, in comparison with demented patients, tended toexaggerate cognitive deficits, show impaired motivation andclassic mood symptoms and have intact language and motorskills.Abram and Alexopoulos 11 described the similarities between theclinical appearances of dementia and depression, including sharedneurovegetative signs, such as weight loss, insomnia, decreasedlibido and fatigue. However, they also emphasized that somedistinctions can be made clinically. Specifically, the authorsasserted that weight loss, fatiguability and insomnia usuallyreflect acute changes in depression, but will be more chronic indementia. Mood-incongruent delusions may be found in psychoticdepression as well as dementia, but mood-congruent delusionsare more characteristic of depression. They also reported that theagitation of dementia often manifests as ‘‘pacing’’, while ‘‘handwringing’’is more characteristic of depression.Other features of the patient’s presentation, as well as personaland family history, can be helpful in distinguishing depressionfrom dementia. Geldmacher and Whitehouse 2 suggested that, inpatients with dementia, more often a relative will report decreasedPrinciples and Practice of Geriatric Psychiatry, 2nd edn. Edited by J. R. M. Copeland, M. T. Abou-Saleh and D. G. Blazer&2002 John Wiley & Sons, Ltd