Depression of Alzheimer disease
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Depression is one of the most common psychiatric symptoms in Alzheimer's disease, occurring at all stages of the disease, but it often appears in a different form than other depressive disorders. In 2000, a workgroup of the U.S. National Institute of Mental Health created a set of provisional diagnostic criteria for depression of Alzheimer disease (dAD) as a separate diagnostic entity in its own right.[1]
In 2005, psychiatrists at Johns Hopkins University School of Medicine created a set of operationalized criteria to aid the diagnosis of dAD in clinical practice.[2]
Although caregivers often feel that the fact of an Alzheimer's diagnosis must be creating depression in the affected person, there is little or no evidence that this is true.[3] In fact, it is not clear how many people are capable of comprehending an Alzheimer's diagnosis at the time it is made. The symptoms of dAD can arise at any point during the course of Alzheimer's disease, often at a stage quite late in cognitive decline.[4]
Numerous neurological studies have found correlations between abnormalities in the brain and depression in dementia. For dAD in particular, positron emission tomography (PET) studies have found alterations of metabolism in the right superior frontal gyrus.[5]
Symptoms
The diagnostic criteria for depression in Alzheimer disease specify that it requires only 3 of the possible symptoms for major depressive disorder (MDD), rather than the 5 required to diagnose MDD itself, and the symptoms may fluctuate. Therefore, dAD often goes unrecognized within the spectrum of symptoms of Alzheimer's disease.[4]
In general, people who have dAD tend to be anxious, agitated, delusional, or inattentive. Symptoms include irritability and social isolation. People with dAD are more likely than those with MDD to show a decline in their enjoyment of social contacts or customary activities, but are less likely to express or experience guilt or feel suicidal.[4]