Some aspects of memory disorders clearly distinguish dementia of the Alzheimer's type from depressive pseudo-dementia.

Two groups of patients affected by mild dementia of the Alzheimer's type (n = 42) or by depressive pseudo-dementia (n = 26) were given a modified version of the Rey's Auditory Verbal Learning Test. The two groups were roughly matched for overall level of cognitive impairment. The main purpose of the research was to determine if some aspects of their memory disorders distinguished the two diagnostic groups. Comparison between results obtained on recall and on recognition measures was of little diagnostic usefulness in distinguishing dementia of the Alzheimer's type (DAT) from depressive pseudo-dementia (DPD). A marked prevalence of the recency over the primary effect in immediate recall, a high rate of forgetting, and the presence of many intrusion errors on delayed recall were observed more frequently in DAT than in DPD patients. None of these indices, however, was sensitive and specific enough to allow a confident diagnostic discrimination at the individual case level. The memory measure which best distinguished DAT from DPD patients was the presence of several false positive errors on delayed recognition because DAT patients adopted a very liberal response bias, endorsing many false recognition errors, whereas DPD patients adopted a conservative criterion and tended to miss real stimuli, rather than making false recognition errors.