Pseudodementia, as the term implies, is a condition that resembles and can be mistaken for dementia. Historically, the term was used to describe reversible deterioration of cognitive function secondary to many conditions, including medical and psychiatric diagnoses. Currently, the term refers primarily to the cognitive impairment seen in patients who have depressive disorders. Recently, it has been replaced by a more descriptive term, namely depression-related cognitive dysfunction. This entry provides an understanding of the term, describes how it differs from dementia, and describes its course and outcome.
Depressive symptoms are quite common in older adults. Population-based studies suggest that nearly 30% of people over 65 years of age show some depressive symptoms. The symptoms of depression in this age group include feelings of sadness; lack of interest in usually enjoyable activities; changes in sleep and appetite; poor energy, motivation, and/or concentration; feelings of hopelessness, worthlessness, and/or excessive guilt; and suicidal thoughts that may be mild (e.g., feeling that life is not worth living) to severe (e.g., intent, plan, and means to end one's life). Many older adults who become depressed can exhibit problems with their cognitive functioning, including memory. C. E. Wells in 1979 distinguished cognitive difficulties associated with depression, termed pseudodementia, from true dementia. Today in doctors' offices, when a patient presents with a new-onset memory complaint, depression is one of the main conditions that needs to be considered in the diagnostic evaluation.
There are several differences between pseudodementia and mild dementia as described by Wells, and some of these differences can be readily elicited in the doctor's office by asking about the patient's medical and psychiatric history. In general, cognitive changes of depression tend to have an abrupt onset and a short course, as opposed to dementia where the cognitive deterioration is gradual. Those patients who primarily have depression often have personal or family histories of depressive symptoms, and these are not common in patients with dementia. Another important difference is in the presentation. Depressed patients are acutely aware of their cognitive dysfunction, may even highlight or exaggerate it, and are distressed by it. On the other hand, demented patients are often unaware of their memory deficits and are often unconcerned about them; if they are somewhat aware, will try to conceal the disability. Typically, demented patients do not seek help from doctors for memory complaints but rather are brought in by family members who have noticed the decline. It is important to note that not all patients with a comparable severity of depression will have cognitive dysfunction; this is a heterogeneous group.
Formal neuropsychological testing carried out by trained psychologists is a more specific way to differentiate between pseudodementia of depression and dementia. Depressed patients are likely to abandon efforts on difficult tests, whereas demented patients will make adequate effort. Depressed patients tend to have inconsistency in test results over time and across a variety of tasks of similar difficulty, whereas demented patients have consistently poor performances. Although both conditions can affect memory, depressed patients are more likely to respond to cueing and do better on memory testing with coaching and feedback, whereas demented patients are not likely to make such gains.
The distinction between pseudodementia and dementia has become increasingly important with the availability of very effective treatment modalities for depression. These include a variety of antidepressant medications that can be well tolerated by the elderly and other biological treatments such as electroconvulsive therapy, which is usually reserved for treatment-resistant depression or the most severe forms of depression. Treatments for dementia are evolving at a slower pace. The most promising so far involve a class of drugs called cholinesterase inhibitors that slow down cognitive decline and may even improve cognitive function, albeit modestly and temporarily. A variety of other treatments are being studied to expand the armamentarium of physicians in fighting dementias.
With effective and adequate treatment of depressive symptoms, cognitive dysfunction can be ameliorated in Page 478 | Top of Articlemany, but not all, patients. These ongoing cognitive impairments may be early signs of co-occurring Alzheimer's disease or vascular dementia. In fact, even in depressed patients whose cognitive symptoms go away altogether after treatment, there is a high rate of subsequent dementia. In a study done by G. S. Alexopoulos and colleagues in 1993, when depressed patients with or without cognitive symptoms were followed for an average of nearly 3 years after recovery, 43% of those with cognitive symptoms of depression went on to be diagnosed with dementia, compared with only 12% of those without cognitive symptoms. This finding has led to the suggestion that depression with cognitive changes, or pseudodementia, may be a harbinger of later dementia. Even so, it is important to recognize the difference and to treat the depression to improve patients' quality of life for possibly several years.
In fact, even in Alzheimer's disease patients, there can be co-occurring depression. Studies in such patients have shown that depression and cognitive status both independently affect the ability to perform day-to-day activities. It then becomes important to treat the depressive component in these patients because doing so may improve functioning, decrease health care costs, and reduce caregiver burden. Thus, regardless of whether all cognitive impairment is reversible, management of the depression is critical.
In conclusion, both depression and dementia can cause memory and cognitive impairment in the elderly. Current research aims at refining the understanding of reversible and irreversible cognitive impairment using neuropsychological and neuroimaging techniques. In the meantime, it is very important to use all available resources to differentiate between the two conditions and to treat each one appropriately.
—Mugdha Ekanath Thakur
Further Readings and References
Alexopoulos GS, Meyers BS, Young RC, Mattis S, Kakuma T. The course of geriatric depression with "reversible dementia": A controlled study. Am J Psychiatry. 1993;150:1693-1699.
Breitner JCS, Welsh KA. An approach to diagnosis and management of memory loss and other cognitive syndromes of aging. Psychiatric Serv. 1995;46:29-35.
Wells CE. Pseudodementia. Am J Psychiatry. 1979;136:895-900.