There is a significantly longer time to a first recurrence of major depressive disorder (MDD) and a lower recurrence risk up to 20 years among adults with more than 3 previous episodes remitted from recurrent MDD and subsequently treated with preventive cognitive therapy (PCT), according to study findings published in Psychotherapy and Psychosomatics.
Long-term study follow-ups for most psychologic interventions max-out at 6 years. The maximum follow-up period for PCT is 10 years (the DELTA study, analyzing the effectiveness of PCT as a recurrence prevention intervention among adults with recurrent MDD). Researchers sought to evaluate the effectiveness of PCT over 20 years, examining number of recurrences, percentage of depression-free time, cumulative proportion of first recurrences, time to first recurrence, and mean severity of recurrences.
They conducted a follow-up of the DELTA study. Entry inclusion criteria for DELTA included adults (18 years and older), a Hamilton Rating Scale for Depression (HRSD) score of no more than 10, in remission from MDD at least 10 weeks but not more than 2 years, and at least 2 previous MDD episodes in the last 5 years. Exclusion criteria included current or previous mania/hypomania, psychotic disorder, predominant anxiety disorder, alcohol/drug misuse, organic brain damage, recent electroconvulsive therapy, recent/current cognitive therapy or current psychotherapy more than 2 times/month.
Participants (recruited at psychiatric centers and through media from February 2000 to September 2000) were randomly assigned to PCT (intention to treat, n=88; 73% women) or treatment as usual (TAU) (intention to treat, n=84; 74% women). During the 8-week intervention period, PCT was administered at weekly 2-hour group sessions. Researchers used ANOVA, Kaplan-Meier analyses, Cox regression analyses, and negative binomial regression, testing for interaction with the number of previous episodes.
Researchers found the overall incidence of recurrence was 91.7% over 20 years (20-year follow-up sample: PCT, n=21, 67% women; TAU, n=17, 94% women). Among the PCT group they estimate 17% experienced no recurrence (vs 14% TAU); 2% had 1 recurrence (vs 3%), 26% had 2-5 recurrences (vs 28%), and 55% had more than 5 recurrences (vs 55% TAU).
They found a significant interaction effect for number of previous episodes with treatment condition on time to first recurrence. Their exploratory analyses suggest there were 53% less recurrences with PCT among participants with more than 3 previous episodes. Among these participants, the percentage of depression-free time was significantly higher with PCT vs TAU, and the cumulative proportion of first recurrences for PCT was 87.5% and for TAU it was 100%. For all participants, over 20 years, there were 23% less recurrences with PCT vs TAU (19% less recurrences vs TAU over the first 10 years; 37% less recurrences vs TAU over the second 10 years).
They noted the mean time to recurrence among participants with more than 3 previous episodes was 4.8 years for PCT vs 1.6 years for TAU. They found no significant effects on mean severity.
Significant study limitations include a not-necessarily-true assumption that the number of recurrences in the full intention-to-treat sample continued after loss to follow-up, the 20-year analyses on time to first recurrence and cumulative proportion of first recurrences based primarily on the first 10-year follow-up period, and PCT beneficial effects may be attributed to differences in other treatments received as a consequence of receiving PCT. Additional limitations include attrition bias, underpowered sample sizes, inability to establish whether any effects were specific to PCT, and differential recall.
Researchers concluded, “Up to 20 years, for MDD patients with more than 3 previous episodes, those who received PCT had significantly longer time to a first recurrence and lower recurrence risk and may have less recurrences and more depression-free time compared to TAU.” They added, “This suggests long term protective effects of PCT up to 20-years.”
Legemaat AM, Burger H, Geurtsen GJ, et al. Effects up to 20-year follow-up of preventive cognitive therapy in adults remitted from recurrent depression: the DELTA study. Psychother Psychosom. Published online December 22, 2022. doi:10.1159/000527906