Verbal learning and memory in depression: a 9-year follow-up study

Memory impairment is often associated with depression. However, the literature is not uniform whether such impairment constitutes state and/or trait characteristics. One-hundred-and-twelve clinically depressed (CDs), previously depressed (PDs), and never depressed (NDs) subjects (T2 diagnostic status),were assessed with the California Verbal Learning Test (CVLT) at T1 and re-assessed 9 years later with the revised version, CVLT-II. At T1 no deficit in verbal memory between CDs and PDs compared to NDs was found, in which the majority of the subjects were younger adults. At follow-up the majority of CDs and PDs had suffered one or several recurrent depressive episodes. Repeated-measures analysis of variance showed, in particular and irrespective of group, a significant decline in recall measures over time. CDs, PDs and NDs showed the same pattern of verbal memory performance over time with the exception of Short Delayed Free Recall, in which CDs and PDs showed a significant decline in performance at follow-up compared to NDs. Likewise, subjects with recurrent depression performed comparable to subjects with a single episode over the course of follow-up. Our results suggest that individuals with mild to moderate unipolar depression may not be significantly affected by verbal memory impairments over the long-term course. The comparability of the versions of the CVLT is addressed.