Depression in Alzheimer's disease: specificity of depressive symptoms using three different clinical criteria

Previous studies report contradictory results on whether the symptoms of depression in Alzheimer's disease patients are the same as in cognitively normal persons. Thus, provisional criteria for depression in Alzheimer's disease (PDC-dAD) have been developed.

To examine which symptoms in AD patients are significant in diagnosing depression according to PDC-dAD compared to those for the DSM-IV-TR and ICD-10 criteria.

We included 112 patients with Alzheimer's disease. They were interviewed by a psychiatrist who diagnosed depression according to PDC-dAD, DSM-IV-TR and ICD-10. Without knowledge of that diagnosis, trained nurses interviewed the caregivers of the patients using the Cornell scale for depression in dementia (CSDD).

Mean age of the patients was 83.0 (s.d. 7.9), 77 (69.6%) were female. The proportion with depression according to each set of criteria was: PDC-dAD 53.5%, ICD-10, 47.3% and DSM-IV-TR, 34.8%. Sadness, loss of interest and agitation/retardation were the most prevalent symptoms in depressed subjects as evaluated by the psychiatrists. According to CSDD sadness, anxiety, suicidal thoughts, poor self-esteem, multiple physical complaints and pessimism best distinguished the depressed patients from the non-depressed. In multiple logistic regression analyses poor self-esteem, delusion and multiple physical complaints best predicted depression using PDC-dAD criteria, whereas sadness, suicidal thoughts and poor self-esteem best predicted depression using ICD-10 and DSM-IV-TR.

The most significant symptoms for a depressive disorder in AD are pretty much the same as for patients without dementia using the DSM-IV-TR and ICD-10 criteria, whereas they differ using the PDC-dAD criteria.