Respiratory and cognitive mediators of treatment change in panic disorder: evidence for intervention specificity

Abstract

Objective: There are numerous theories of panic disorder, each proposing a unique pathway of change leading to treatment success. However, little is known about whether improvements in proposed mediators are indeed associated with treatment outcomes and whether these mediators are specific to particular treatment modalities. Our purpose in this study was to analyze pathways of change in theoretically distinct interventions using longitudinal, moderated mediation analyses.

Method: Forty-one patients with panic disorder and agoraphobia were randomly assigned to receive 4 weeks of training aimed at altering either respiration (capnometry-assisted respiratory training) or panic-related cognitions (cognitive training). Changes in respiration (PCO₂, respiration rate), symptom appraisal, and a modality-nonspecific mediator (perceived control) were considered as possible mediators.

Results: The reductions in panic symptom severity and panic-related cognitions and the improvements in perceived control were significant and comparable in both treatment groups. Capnometry-assisted respiratory training, but not cognitive training, led to corrections from initially hypocapnic to normocapnic levels. Moderated mediation and temporal analyses suggested that in capnometry-assisted respiratory training, PCO₂ unidirectionally mediated and preceded changes in symptom appraisal and perceived control and was unidirectionally associated with changes in panic symptom severity. In cognitive training, reductions in symptom appraisal were bidirectionally associated with perceived control and panic symptom severity. In addition, perceived control was bidirectionally related to panic symptom severity in both treatment conditions.

Conclusion: The findings suggest that reductions in panic symptom severity can be achieved through different pathways, consistent with the underlying models.

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Figures

Figure 1

Participant flow diagram. CART = capnometry-assisted respiratory training; CT = cognitive skill training.

Figure 2

The multimediator model (a) and models summarizing the significant mediated pathways for CART and CT (b and c). Each measure was standardized for this analysis. The path coefficients shown are the regression coefficients from the MLM analyses represented in the path diagram. These coefficients are equivalent to standardized regression coefficients, as the variables were standardized. If a path is moderated by treatment condition, both CT and CART are marked with a degree sign. PCO2 = partial pressure of carbon dioxide; CART = capnometry-assisted respiratory training; CT = cognitive skill training; MLM = multilevel modeling. * p < .05. ** p < .01.

Figure 3

Models representing cross-lag panel analyses for CART. Each measure was standardized for these analyses. The path coefficients shown are the regression coefficients from the MLM analyses represented in the path diagram. These coefficients are equivalent to standardized regression coefficients, as the variables are z-scored. All coefficients are for the CART condition. None of the cross-lag coefficients were significant for CT. PCO2 = partial pressure of carbon dioxide; CART = capnometry-assisted respiratory training; CT = cognitive skill training; MLM = multilevel modeling. * p < .05. ** p < .01.