This Pilot Randomized Controlled Trial (RCT) overall aim is to establish the safety, feasibility, acceptability and preliminary effects of a body-oriented psychotherapy, Somatic Experiencing (SE), on social functioning and mental health among adults with a history of Child Maltreatment (CM) and symptoms of posttraumatic stress disorder (PTSD) or complex posttraumatic stress disorder (CPTSD). Participants will be randomized either to an SE-group (n=25, psychoeducation, and information about treatment possibilities + 15-session SE treatment) or to a control group (n=25, same psychoeducation and information about treatment possibilities + regular phone calls to provide updates on their well-being and if they started a treatment). Given the lack of research on the effect of SE on Psychological Safety in this population, while SE has not yet been introduced into the Swedish health care system, special consideration will be given to participant safety, feasibility and acceptability of the SE-treatment. This includes monitoring (and assessing) for serious adverse events (SAEs) and adverse events (AEs), if conducting an RCT on SE in our target sample is feasible (e.g., achieving the target sample goal, assessing attrition rates and session attendance) and the acceptance of the used SE intervention (e.g., positive evaluations and willingness to recommend the treatment). Next to assessing safety, feasibility and acceptability, preliminary outcomes (self-report and experimental measures) will be evaluated at pre-treatment, post-treatment (20 weeks after pre), and at a 20-week follow-up, assessing primary outcomes (Psychological Safety) and secondary outcomes (Social Safeness, PTSD, CPTSD, Depression), as well as additional factors (e.g., interoception) that could contribute to decreased mental health and social functioning issues. Additionally, participants' behavioral (e.g., interpersonal distance) and physiological responses (HR, HRV, EDA) to social stimuli will be assessed pre- and post-treatment in an experimental setup to explore SE's potential to reduce Negative Affect and increase Positive Affect (Activated, Relaxed, Safe/Content) in response to social stress.

Adults with a history of CM may struggle with psychological safety on both an emotional and physiological level, such as interpreting neutral facial expressions as negative/threatening or experiencing distress when approaching or being approached by others (Lüönd et al., 2022; Pfaltz et al., 2019). However, just as the social environment can be perceived as threatening, adults with CM-history can also experience absence of safety cues (e.g., perceived social support) which not only heightens the risk of developing and maintaining PTSD and CPTSD (Scott et al., 2023), but also impair social functioning further (cf. Pfaltz et al., 2022).

Although effective interventions like trauma-focused CBT exist for treating mental disorders such as PTSD (Lewis et al., 2020), they less often focus on facilitating feelings related to psychological safety such as social safeness (i.e., the extent to which individuals perceive their world as safe, warm, and soothing). This is problematic because exaggerated stress reactions and somatic symptoms may persist after treatment (Larsen et al., 2019) and social safeness could be a protective factor against these symptoms (Gilbert, 2020). Studies have e.g. shown that the presence of a friend can reduce stress reactions in individuals exposed to social stress (Heinrichs et al., 2003), and exposure to safety-related texts/images can reduce exaggerated stress responses to threatening situations (Gillath & Karantzas, 2019). Thus, social safeness may be crucial for regulating affective states.

Therefore, it is necessary to evaluate interventions that not only reduce symptoms of mental disorders but also actively focus on facilitating social, emotional, and body sensations related to feeling safe, particularly for individuals with CM-histories that not only suffer from mental disorders, but also lack protective factors that could inhibit it, such as caring support from others or self. One potential intervention is SE, a body-oriented approach (Levine, 1997). Unlike CBT and exposure-based interventions, SE focuses more on interoception and musculoskeletal sensations rather than primary focus on cognitions to promote affective self-regulation and resilience to stress (Payne, 2015). Through SE, clients are assumed to learn to manage unpleasant emotions and reduce negative bodily reactions, while identifying positive bodily sensations that provide safety and calmness. This might help clients to be present in their surroundings and potentially restore their ability to feel socially safe both physically and psychologically.

Preliminary results from our own (to be published) studies show that SE has a short-term effect (one session) on increased perceived psychological safety in adults with a history of CM compared to a control group. Systematic reviews and meta-analyses have as well indicated that SE can reduce symptoms of PTSD, depression, and somatic symptoms (Heim et al., 2023; Kuhfuß et al., 2021). However, there is a research gap concerning the feasibility, acceptability and preliminary long-term effects of SE on facilitating psychological safety in individuals with a history of CM and PTSD/CPTSD symptoms.

Accordingly, we will conduct a pilot RCT, adhering to the Consolidated Standards of Reporting Trials (Schulz, 2010), to evaluate the feasibility of SE, acceptability, and safety as well as to explore the potential of SE (preliminary outcomes) for improving social functioning and mental health for adult participants with a CM-history and symptoms of (C)PTSD. Participants meeting these criteria will be randomly allocated to either an SE-group (n=25) or to a control group (n=25). Self-report measures will be collected pre, post-treatment, and at a 20-week FU assessing primary outcomes (Psychological Safety) and secondary outcomes (Social Safeness, PTSD, CPTSD, Depression, Sense of Disrupted Body Boundaries, Interoceptive Awareness, Attachment style, Social Support, and Somatic symptoms). Potential influencing variables (Socio-Demographics, Attitudes towards Psychotherapy, CM history, Attachment style, Interoceptive Awareness, Social Phobia, and Therapeutic Alliance) will be analyzed to explore potential mechanisms of treatment responses in primary and secondary outcomes. Moreover, participants will attend a physical visit (experimental study part) at Stockholm University (SU) where we assess behavioral (e.g., interpersonal distance), physiological responses (HR, HRV and EDA) and affective responses (e.g., negative affect) to social stimuli (e.g., facial expressions).

In addition to primarily assessing safety, feasibility and acceptability of the intervention (See brief summary), we will test the following hypotheses regarding preliminary effects of the intervention:

Primary hypothesis (Primary outcomes):

1. Participants in the SE-group, compared to the control group, will show higher levels of Psychological Safety at post-treatment and FU.

   Secondary hypothesis (Secondary outcomes):

2. Participants in the SE-group, compared to the control group, will show higher levels of Social Safeness at post-treatment and FU.

3. Participants in the SE-group, compared to the control group, will show lower levels of PTSD, CPTSD, Depression, Sense of Disrupted Body Boundaries and Somatic Symptoms at post-treatment and FU.

4. Participants in the SE-group, compared to the control group, will show higher levels of Attachment Security, Interoceptive Awareness, and Social Support at post-treatment and FU. 5. Based on preliminary results from our short-term intervention study, higher levels of CM will predict a stronger treatment response, indicated by a stronger increase in Psychological Safety in the SE-group compared to the control group.

Hypotheses related to the experimental study part:

6. Participants in the SE-group, compared to the control group, will rate neutral facial expressions less negatively from pre- to post-treatment.

7. Participants in the SE-group, compared to the control group, will show greater decrease in preferred interpersonal distance from pre- to post-treatment.

8. Participants in the SE-group, compared to the control group, will show improved affective/physiological self-regulation (self-reports on TPAS, body sensations, higher HRV, lower HR, and decreased EDA response) following exposure to attachment primes (recalling and visualization interpersonal insecure and secure attachment-related experiences) from pre- to post-treatment.

Method

To characterize the sample (presence of mental disorders) and to assess exclusion criteria we will employ sections of the MINI (Sheehan et al., 1998) that is relevant for our study population.

Before randomization, participants will complete four experimental paradigms at SU, including: "stop-distance task," (measuring participants' preferred physical distance towards strangers, see Lüönd et al., 2022) and a "rope exercise" measuring safety within one's personal space (for exploratory purposes). Then, the participants' physiological (HR, HRV, EDA) and self-reported responses to facial expressions (Pfaltz et al., 2019) will be assessed. Lastly, the participants' affective (self-reported) and physiological (HR, HRV, EDA) self-regulation in response to attachment primes (described above) will be evaluated. After the physical visit, randomization to SE or control will take place.

Adverse events (AEs) will be defined as any unfavorable medical occurrences or undesirable experiences (e.g., suicidal thoughts, dependency, symptom worsening, hopelessness, failure, stigma, quality of treatment) encountered by participants during the study-period, regardless of their relation to the study.

All participants will complete symptom scales (ITQ and PHQ9) at pre, repeatedly during, post and at FU. A symptom increases on ITQ from pre to any of the follow-up measurement points of 50% - 79% is considered an AE, an increase of 80% or more is considered a SAE. If participants score ≥ 1 on suicidality item 9 (PHQ-9) at any of the measurement points, we will conduct a risk assessment and based on this determine if one of the following applies: (i) death by suicide; (ii) suicide attempt; (iii) suicidal crisis without attempt; (iv) self-harming behaviors and thoughts of self-harm.

(i) - (iv) are counted as SAE if they:

1. result in death and/or:
2. are life-threatening
3. require hospitalization or prolongation of existing hospitalization
4. result in significant disability or incapacity Thoughts and behaviors that do not result in a), b), c), or d) will be considered AE.

Determination of whether an (S)AEs is related to the SE-treatment will be based on whether the event is unexpected or unexplained given participants' clinical development, previous medical conditions, medications or interventions. An AE form will be provided to therapists for completion at the end of each session, instructed to report AEs within 24 hours and SAEs directly to the research team, who will review (and consult with a psychiatrist in the project) and assess the nature of each event(s) to decide on appropriate actions such as potential participant withdrawal of the study.

At post-treatment, AEs will be assessed using the NEQ. Feasibility and acceptability will be evaluated via participant-written evaluations, analyzed both quantitatively (e.g., percent of satisfactory with SE and recommend SE to others) and qualitatively (e.g., thematic analysis). All SE sessions will be audio-recorded for exploratory analysis and to assess treatment integrity and fidelity. A random selection of sessions will be independently scored, by an independent assessor, for fidelity to ensure adherence to the treatment manual.

There are no efficacy studies on longitudinal interventions for Psychological Safety, to enable adequate a priori power calculations and resource constraints allowing for a sample size (approximately n=25 in each group), our study will follow Lakens (2022) recommendations: assessing precision via confidence interval widths and explore detectable effect sizes across various power levels via sensitivity power analysis. Based on the outcome, the BUCSS R package (See Anderson et al., 2017) for implementing Bias- and Uncertainty-Corrected Sample Size, a method of correcting for publication bias and uncertainty when planning sample sizes in a future study from an original study.

Analyses will follow an intention-to-treat approach, including all randomized participants, even those who do not complete the study. For primary and secondary outcomes, we plan to use linear mixed models to handle missing data, assuming data are missing at random. Time (pre, post, treatment, and FU) and Group (SE vs. control) will be fixed effects, with participants as random effects. Treatment efficacy will be indicated by a significant time-by-treatment interaction. Potential moderators influencing treatment effects will be analyzed as covariates in the mixed model analysis. Clinically significant changes in (C)PTSD and Depression scores will be analyzed by calculating a Reliable Change Index (RCI), classified as "improved," "worsened," or "unchanged" based on changes in symptom scores exceeding relevant RCI values (See Cloitre et al. 2021). Behavioral and physiological responses at the experimental study part will be analyzed using a similar analytic approach (linear mixed models) or ANOVA. HRV measurement will include both common frequency estimates (e.g., HF) and time domain estimates (e.g., rMSSD).

Outliers will be identified using univariate and multivariate detection methods, such as Cook's distance (with values >1 indicating an outlier) and standardized residuals (±3.29 indicating an outlier, Tabachnick & Fidell, 2013). If outliers are identified, we aim to present results both with outliers, and with the adjustment for outliers, and/or consider using robust maximum likelihood (MLR) estimation, which is more robust against outliers.

Inclusion Criteria:

• Adults (18 years or older).
• Proficiency in Swedish Language.
• Access to a computer/internet.
• Meeting CTQ-cutoff for CM history (CTQ rating higher than 'none / minimal' in at least one of the subscales according to Bernstein and Fink (1998) (i.e. ≥10 for emotional neglect, ≥ 8 for physical neglect, ≥9 for emotional abuse, ≥8 for physical abuse and ≥6 for sexual abuse).
• Meeting at least moderate/severe PTSD or complex PTSD symptoms on the ITQ.
• If taking medication, it must have been ongoing for at least 3 months and the dose must have been stable for 1 month.
• Signed informed consent provided.

Exclusion Criteria:

• Participants screen positive for alcohol (AUDIT) or substance abuse (DUDIT).
• Psychotic symptoms, ongoing manic episode, acute suicidality.
• If ongoing medication has an impact on the physiological data (ECG) recorded during the social paradigms, physiological data will be excluded from the analyses (but not exclusion for the treatment).
• Have current (pre-assessment) ongoing psychological treatment focusing on social safeness, PTSD or complex PTSD.