Phenomenology of Depression in Alzheimer's Disease

Depression is among the most frequent psychiatric comorbid conditions in dementia. There is no strong consensus as to what criteria should be used to diagnose depression in AD. This is at least partially explained by the overlap between symptoms of depression and symptoms of AD. Recent studies using latent class analysis provided clarification to this diagnostic dilemma. All nine DSM-IV symptoms of major depression were found to characterize a class with a high chance (96%) of having a clinical diagnosis of major depression, and symptoms of anxiety were also frequent. Other psychiatric symptoms may also be included under the construct of depression in AD, since both apathy and anxiety are among the most frequent comorbid conditions for major depression in AD. Subtypes of depression should also be validated in this condition. For instance, increased awareness of cognitive and functional deficits is significantly associated with dysthymia but not with major depression, suggesting that different depressive syndromes in AD may have different etiology.