Within-day sudden gains and generalized anxiety disorder psychotherapy outcome.

According to dynamic systems theory, initial symptom instability is necessary for long-term stable change to occur from psychotherapy. Such instability may be assessed using within-day sudden gains (SGs), sudden losses (SLs), and reversals. The present study examined these symptom change patterns and their association with treatment outcome using intensive diary assessment across three psychotherapies for generalized anxiety disorder (GAD). In a secondary analysis of Borkovec and Costello (1993), 59 clients diagnosed with GAD were randomly assigned to applied relaxation (AR; = 21), cognitive behavioral therapy (CBT; = 20), or nondirective (ND) therapy ( = 18). Clients completed thrice daily anxiety ratings while receiving psychotherapy. The occurrence of SGs, SLs, and reversals assessed for each individual was calculated using changes between each assessment. We examined the association between occurrence of SGs, SLs, and reversals and symptom change from pretreatment to posttreatment, and 6-month, and 1-year follow-up. Clients in ND (61.1%) were more likely to experience SGs than clients in CBT (20.0%) or AR (38.0%). 92.9% of SGs were followed by a reversal. Experiencing SGs was associated with less symptom change from pretreatment to follow-up in ND and not associated with outcome in CBT or AR. SLs and reversals were not associated with outcome. When measured at a within-day level, SGs are very likely to be reversed and may be associated with poorer long-term outcome in ND. Within-day SGs may have a fundamentally different meaning than session-to-session SGs. (PsycInfo Database Record (c) 2022 APA, all rights reserved).