When depression creates cognitive symptoms that look like Alzheimer's or another type of dementia, it's often referred to as pseudodementia. Diagnosing pseudodementia is complicated, but a thorough examination can reveal important clues.
For instance, people with depression might complain about their memory, but they often do well on mental status exams and other tests that evaluate cognitive function. On the other hand, those with dementia often deny any memory problems but don't do as well on mental status exams and similar tests. Also, a depressed person is less likely to show severe mood swings, whereas someone with dementia shows a wider range of emotions and sometimes makes inappropriate emotional responses (e.g., laughing while others are sad).
The Geriatric Depression Scale (GDS) is a screening instrument used to detect depression among older adults. The GDS should be one of several methods used in an evaluation. Older adults might have depression that looks like Alzheimer's, or they might have both depression and Alzheimer's or another dementia. If depression is detected, it can be treated alongside other disorders, such as Alzheimer's disease.
Depression can be reversed, but treating it can be as complex as treating Alzheimer's. While symptoms don't go away immediately, depression often responds well to a combination of antidepressant medication and psychotherapy. People who have depression may experience relapses, so it's important to find a qualified professional or health care team to treat it, whether or not the depression occurs alongside Alzheimer's.
Sources:
American Psychiatric Association (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author.
Hill, C. L., & Spengler, P. M. (1997). Dementia and depression: A process model for differential diagnosis. Journal of Mental Health Counseling, 19, 23-39.
Yesavage, J., Brink, T., Rose, T., Lum, O., Huang, V., Adey, M., & Leirer, V. (1983). Development and validation of a geriatric depression screening scale: A preliminary report. Journal of Psychiatric Research, 17, 37-49.
