Objective: Memory impairment in remitted depression is reported to be related to the number of previous depressive episodes. A recent report hypothesized that each depressive episode increases the risk of memory impairment during remission, which further increases the risk of recurrence. We investigated whether the risk for recurrence increased as a function of memory impairment at remission.
Method: One hundred ten participants with DSM-IV-TR major depressive disorder (MDD) after remission (defined as a score ≤ 7 on the Hamilton Depression Rating Scale) were recruited between April 2004 and March 2012 and were followed up prospectively. All patients were divided into 2 groups: those who had memory impairment and those who had no memory impairment after remission. (Memory impairment was determined with the Wechsler Memory Scale-Revised.) The time to recurrence of depression (a score ≥ 4 on the Clinical Global Impressions-Severity of Illness scale) was compared between the groups prospectively. Kaplan-Meier survival curves, log-rank test for trend for survivor functions, and Cox proportional hazard ratio (HR) estimates for a multivariate model were conducted to examine the risk of recurrence by presence of memory impairment after remission.
Results: One hundred nine participants completed this study. In the follow-up period, recurrence occurred in 25 (55.6%) of the 45 patients with memory impairment and 21 (32.8%) of the 64 patients with no memory impairment. In the Kaplan-Meier survival estimates for time to incidence of recurrence in patients with and without memory impairment, the cumulative probability of developing a recurrence for patients with memory impairment was higher than for patients with no memory impairment (log-rank test: χ(2)1 = 4.63, P = .03). Survival analysis was also performed using Cox proportional hazards regression in a multivariate model. The presence of memory impairment remained significantly associated with incidence of recurrence (HR = 2.55; 95% CI, 1.30-4.99; P = .006).
Conclusions: The presence of residual memory impairment in patients with remitted MDD may increase the risk of recurrence.
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