NEST: A Group Intervention for Parents With Complex PTSD

Participants receive the NEST group intervention, a manualized, trauma-informed program comprising nine weekly 90-minute group sessions co-led by a member of the study team and a mental health professional from the treatment site. Sessions address parenting-related challenges associated with Complex PTSD, including self-efficacy as a parent, emotion regulation within the parent-child relationship, setting boundaries, and age-appropriate communication with children about the parent's diagnosis. All participants complete self-report questionnaires at three time points (T0, T1, T2) and a subset also completes a semi-structured qualitative interview at T1.

The NEST group intervention is a manualized, trauma-informed program consisting of nine weekly 90-minute group sessions, co-led by a member of the study team and a mental health professional from the treatment site. Groups are closed and comprise 6-8 parents. Sessions address parenting-related challenges associated with Complex PTSD, including self-concept and self-efficacy as a parent, emotion regulation within the parent-child relationship, setting boundaries, regulating closeness and distance in the parent-child relationship, and age-appropriate communication with children about the parent's diagnosis. Sessions are trauma-sensitive but not trauma-focused; traumatic memories are not processed within the group.

• NEST - Nurturing Emotional Safety in Trauma-Affected Parenting

Feasibility will be assessed descriptively by the number of participants enrolled and the time required to reach the planned sample size.

Retention will be assessed as the proportion of participants completing the post-intervention assessment (T1). A retention rate ≥70% at T1 is defined a priori as the benchmark for implementation-readiness.

Adherence will be assessed as the proportion of participants attending at least 7 of 9 group sessions. A rate of ≥70% of participants attending at least 7 of 9 sessions is defined a priori as the benchmark for implementation-readiness.

Feasibility will be assessed descriptively through documentation of protocol deviations occurring during the intervention.

Acceptability will be assessed using the generic Theoretical Framework of Acceptability questionnaire (TFA; Sekhon et al., 2022), translated into German and adapted to the group therapy context. The TFA covers seven constructs (affective attitude, burden, ethicality, intervention coherence, opportunity costs, perceived effectiveness, self-efficacy) plus a general acceptability item. Acceptability is considered sufficient if ratings indicate an overall positive evaluation.

A subset of participants will additionally complete a semi-structured qualitative interview (approximately 40-50 minutes) exploring their experience of the intervention. Acceptability is considered sufficient if no substantial recurring concerns regarding safety, burden, or contextual fit emerge in qualitative findings.

Assessed using the International Trauma Questionnaire with Clinical Checks (ITQ-CC; Shevlin et al., 2025; German version: Kratzer et al., 2025), which measures ICD-11 PTSD and Complex PTSD symptom severity, including disturbances in self-organisation. Changes in total and/or subscale scores across time points will be analysed descriptively and exploratively.

Assessed using the Parental Stress Scale (PSS; Berry & Jones, 1995; German validation: Kölch et al., 2022), an 18-item measure of parenting-related stress across positive and negative dimensions of the parenting role. Changes in total and/or subscale scores across time points will be analysed descriptively and exploratively.

Assessed using the Brief Parental Self-Efficacy Scale (BPSES; Woolgar et al., 2025), a 5-item measure of parents' perceived competence and confidence in their parenting role. Changes in total score across time points will be analysed descriptively and exploratively.

Assessed using the Parenting Scale Short Form (PS-8; Kliem et al., 2018), an 8-item measure of dysfunctional discipline practices, comprising two subscales - laxness and overreactivity - developed and validated in a German representative population sample. Changes in total and/or subscale scores across time points will be analysed descriptively and exploratively.

Assessed using the Parental Reflective Functioning Questionnaire (PRFQ; Luyten et al., 2017; German validation: Wildner et al., 2024), a 16-item measure of parents' capacity to mentalise in relation to their child, across three subscales: certainty about mental states, interest and curiosity, and pre-mentalising modes. Changes in total and/or subscale scores across time points will be analysed descriptively and exploratively.

Assessed using the Family Assessment Device - Affective Responsiveness subscale (FAD-AR; Miller et al., 1985; German validation: Beierlein et al., 2017), a 7-item subscale assessing the quality of emotional responsiveness within the family. Changes in score across time points will be analysed descriptively and exploratively.