This study examined the occurrence of sudden gains in psychotherapy for the treatment of PTSD. Consistent with our hypothesis, sudden gains do appear to occur in CBT for PTSD and happen at similar rates to sudden gains in the treatment of depression. There were no statistically significant differences in the frequency of sudden PTSD gains between the three treatment conditions most likely due to the small sample sizes per cell. However, the similarity across treatments may also be attributable to the presence of common therapeutic interventions found in the three cognitive–behavioral treatments, such as those targeting avoidance and directly addressing traumatic material. Further, consistent with current cognitive–behavioral theories of PTSD, different interventions with different routes to changing the same mechanisms may be at work, resulting in similar rates of sudden gains in the course of treatment (Foa, Rothbaum, Riggs, & Murdock, 1991
). Future research should be conducted to clarify whether there are similar mechanisms in different therapies leading to sudden improved treatment outcome across therapeutic interventions.
This study also suggests that participants who experience a sudden gain during the course of PTSD treatment will have greater symptom reductions at the end of treatment compared with those who do not experience such a gain. However, the presence of a sudden gain during treatment does not appear to be associated with the amount of symptom reduction at follow-up. Although these findings call into question the importance of a sudden gain in predicting sustained response to PTSD treatment, they suggest that sudden gains may be important to the efficiency of therapies. In other words, those experiencing sudden gains may respond to treatment more quickly. However, a potential alternative explanation is simply that the PTSD results are an artifact of the definition of sudden gain and regression to the mean. Further, the timing of sudden gains in PTSD treatment may be different across therapies, but we were not able to compare when the sudden gains occurred in the three treatments due to limitations in the number of assessments given over the course of treatment and the small sample sizes. Therefore, more research is needed in this area, as it will be critical to better understand whether mechanisms at work in the beginning or end of treatment are more important to treatment outcome, both immediate and long-term (6-month follow-up).
In examining PTSD symptom clusters, this study indicates that sudden gains are similarly associated with change in avoidance/numbing and hyperarousal symptoms, i.e., sudden gains are associated with greater symptom reduction at the end of treatment, but not at follow-up. In contrast, a different pattern emerged in the reexperiencing symptom cluster. The results showed neither significant time by sudden gain group interaction nor a sudden gain group main effect. It appears that PTSD sudden gains, as measured by self-report PDS scores, are largely driven by changes in avoidance/numbing and hyperarousal symptoms, and not by changes in reexperiencing symptoms. There is some evidence that high levels of reexperiencing symptoms make it more difficult to be cognitively flexible, given the amount of cognitive resources taken up by these symptoms (Hellawell & Brewin, 2002
; Shipherd & Salters-Pedneault, 2008
; Vasterling & Brailey, 2005
). Thus, patients with these significant cognitive intrusions may be less able to experience a cognitive shift or sudden gain during treatment.
Although sudden gains may not be uniquely predictive of longer-term PTSD outcomes, our study indicates that sudden gains are important in comorbid depression outcomes. We found that participants who had sudden gains in PTSD symptoms during treatment had significantly lower levels of depression at the end of treatment and at 6-month follow-up compared with those who did not evidence a sudden gain. Moreover, post hoc analyses suggest that the effects were not due to sudden gains in depression symptoms. This pattern of findings reinforces the notion that there are different processes underlying PTSD and depression, and that cognitive shifts may, in turn, be more or less relevant to these mechanisms. These findings are particularly relevant to better understanding the possible differences in mechanisms of action in PTSD treatment compared with depression treatment, but more research is needed to determine the differences of therapy process in PTSD and co-occurring depression.
As with other studies of sudden gains, a potential limitation of this study was the reliance on a self-report measure to determine sudden gains. However, because the study of sudden gains requires the use of repeated measurements, a more thorough interview-based assessment is not practical. The nature of the sample (i.e., exclusively female, PTSD from sexual or physical assault) requires that this study be replicated with more diverse samples to assess the generalizability of the findings. Another limitation of this study, in comparison with other sudden gain studies, is that only PDS scores from every other session were available for two of the three treatment conditions. As a result, we altered the sudden gain criteria in this study. This change may have inflated the number of individuals meeting the criteria because these sudden gains calculations are based on differences between two therapy sessions instead of one. On the other hand, the PDS was administered weekly, thus allowing for the calculation of sudden gains based on weekly measurements, which is comparable to other studies (Gaynor et al., 2003
; Tang et al., 2002
; Vittengl, Clark, & Jarrett, 2005
). Additionally, only a limited number of sudden gains were possible, given the criteria and the duration of the therapies (i.e., 6 weeks). Thus, it is possible that the percentage of sudden gains found in this study may be an overestimate of the percentage of participants who will experience a sudden gain in more natural treatment settings. Because this is the first study of its kind, it is important that this be a launching point for more research in this area.
Future research is also needed in the area of mechanisms of change in cognitive–behavioral psychotherapies for PTSD. Although this article outlines the relationship between sudden gains and PTSD treatment outcome, further research is needed to examine the process of sudden gains in PTSD treatment. It seems important to identify what specifically occurs in treatment just prior to a sudden gain so that overall therapy can be enhanced. This objective was beyond the scope of this study. Future research may ultimately lead to briefer, more efficient therapies, and greater knowledge gained about potential critical sessions could lead to more effective evidence-based therapies for PTSD.