Dementia and Depressive Pseudodementia: Differential Diagnosis
One of the things that neurocognitive testing is very good at it is helping distinguish
between dementia and dementia-like symptoms that are brought about by depression. The
latter occurs fairly frequently, especially among the elderly. Individuals with severe
depression can display extreme psychomotor slowing, which inhibits their ability to
rapidly perform a variety of mental operations. These individuals can display profound
concentration problems, and their inability to focus attention can bring about variable
performance in memory and problem-solving tasks. These issues can mimic those seen in
progressive dementing processes.
Obviously, differential diagnosis regarding this issue has profound implications in regard
to treatment strategies, placement issues, and the potential for activation of a durable
power of attorney arrangement or the need for legal guardianship or conservatorship.
There several factors that neuropsychologists look for in attempting to make this
discrimination. Obviously, the first is the presence of severe and debilitating depression.
An individual who has a history of depressive episodes is more likely to display a
depressive pseudodementia than a peer who has no such history. Obviously, mild
depression, transient periods of unhappiness, or a long-standing, "low-grade" depression
would be unlikely to bring about cognitive impairment. The patient's mood disorder
should be formally assessed, if possible, through objective psychological testing such that
one can attain an empirical estimate of the level of depression is present.
The patient's presentation can also be a clue as to the presence or absence of dementia. In
dementia after the initial stages, patients often display "la belle indifference”, or "the
beautiful indifference". This is sometimes seen in the neglect of defcits observed in head
injury patients, but is often also the case in dementia patients who are relatively unaware
of the severity of their cognitive issues. Pseudodementia patients, on the other hand, are
often (but not always) exceedingly focused on their deficits. They may complain bitterly
about their inability to perform various cognitive tasks, and they may have a generally
negative appraisal of their abilities.
Another clue to this personality structure can be obtained in objective psychological
testing. These patients can have a tendency to display a great deal of focus on somatic
issues and at times display histrionic characteristics on the MMPI-2. The presence of this
focus on somatic, psychiatric, or cognitive issues is a good reason to conduct objective
psychological testing with these patients, if one is able to do so given the level of
inattention present. As an alternative, we sometimes choose to read the MCMI-III to the
patient, but I personally find this assessment tool is somewhat less helpful in making
these determinations than the MMPI.
In addition, and neuropsychologists look at the pattern of deficits displayed by a patient
to help make a determination between dementia and a depressive pseudodementia. There
are various and specific deficits displayed on subtests that, in isolation, are quite
indicative of the presence of cognitive difficulties related to mood disturbance as opposed
to organic illness. For example, the initiation/perseveration subtest of the Dementia
Rating Scale is a good indicator of psychomotor slowing and difficulties initiating mental
operations. A low score on this subtest without accompanying deficits in measured
memory functioning is often a strong indicator of the existence of a depressive
pseudodementia.
Making this differential diagnosis involves savvy use of objective psychological testing
techniques, a good understanding of cognitive testing techniques, and to certain extent
requires a clinician that has experience seeing many patients with various types of
dementia is and with depressive pseudodementia issues. The ability to make this
differential diagnosis can often significantly and positively influence the quality of life
for the individuals involved, this is one of the more gratifying aspects of providing
neurocognitive testing for older adults.