Emotion dynamics and somatic symptoms in everyday life: Ecological momentary assessment in somatic symptom disorder...

Negative affectivity (NA) is associated with the emergence and persistence of physical symptoms with unclear organic pathology. This study investigated the temporal dynamics of NA and somatic symptom burden using ecological momentary assessment (EMA) in adults with somatic symptom disorder (SSD) and healthy control participants (HC).

Participants underwent a seven-day, smartphone-based EMA, with 6 randomly-stratified time points per day. NA was assessed using a five-item short form of the Positive and Negative Affectivity Scale (PANAS) and somatic symptom burden with two self-constructed items. 22 persons with SSD and 20 HCs were included in multilevel analyses.

Within-person analyses showed a significantly stronger (positive) association of concurrent NA with somatic symptom burden in participants with SSD than in HCs, β = 0.15, SE = 0.04, p = .001. Time-lagged analyses demonstrated that, across groups, NA at a previous time point t-1 significantly predicted somatic symptom burden at the subsequent timepoint t, β = 0.09, SE = 0.03, p = .005, but not in the other direction (somatic symptom burden_t-1→ NA_t, β = 0.01, SE = 0.04, p = .79). Between-person analyses showed that both inertia (i.e., persistence of negative affective states), d = 0.74, and instability (i.e., magnitude of moment-to-moment fluctuations), d = 0.76 of NA were significantly higher in participants with SSD than in HCs.

Our findings sustain the idea of (negative) affect-driven modulation in somatic signal processing and suggest that interoceptive and emotional differentiation training can advance the psychotherapeutic treatment of SSD.