Session-level emotional processing and subsequent somatic symptom change in online ISTDP for treatment-resistant...

Difficulties in emotional processing are implicated in the development and maintenance of Somatic Symptom Disorder (SSD) and may represent a target for therapeutic change. This study examined whether session-level emotional processing, operationalized as "rise in complex feelings", predicts subsequent reductions in somatic symptoms during online Intensive Short-Term Dynamic Psychotherapy (ISTDP) for treatment-resistant SSD.

Twenty-five participants with moderate to severe SSD and non-response across two prior intervention phases received up to 16 sessions of online ISTDP (M = 14.1) delivered by 17 therapists. After each session, therapists rated rise in complex feelings (0-6), reflecting emotional processing within the therapeutic relationship. Somatic symptom severity was assessed weekly using the Patient Health Questionnaire-15 (PHQ-15). Lagged multilevel models tested whether rise predicted the subsequent PHQ-15 assessment, with person-mean centering isolating within-person effects. A one-sided test evaluated the a priori directional hypothesis.

Higher-than-usual rise in complex feelings was associated with lower somatic symptom severity at the subsequent assessment (b = -0.22, 95% CI [-0.43, -0.02], one-sided p = .016, two-sided p = .032). The association was robust across sensitivity analyses, including reverse temporal ordering. Adjustment for patient-rated emotional activation and therapeutic alliance only modestly attenuated the estimate. The association was observed within-person; between-person differences in average rise were unrelated to symptom outcomes (b = -0.03, p = .809).

Session-level emotional processing was associated with subsequent reductions in somatic symptoms in online ISTDP, providing preliminary evidence that emotional processing may represent a session-level marker of symptom change in SSD.