The Effects of the Safe and Sound Protocol on PTSD Symptoms and Anxiety
Phase: NA
Conditions: Post Traumatic Stress Disorder, Anxiety
Sponsor: Indiana University

 
 
 
 
The effects of the Safe and Sound Protocol on PTSD symptoms and anxiety in trauma survivors: 
An observational pilot study 
 
Updated: March 27, 2025 

 
 
 Background & Rationale 
Population-based studies from a range of countries show that a majority of adults will experience 
a traumatic event at some point in their life (Benjet et al., 2016; Burri & Maercker, 2014) and many of 
these experiences – such as sexual assault, combat experience, or actual or threatened injury – are known 
triggers for post-traumatic stress disorder (Kessler et al., 2017). PTSD is defined by a cluster of 
phenomena that include alterations in brain-body patterns of arousal and reactivity which can manifest in 
irritability and aggression, hypervigilance, which may be caused or maintained by threat-responsive 
tuning of the autonomic nervous system (Kolacz, Kovacic, & Porges, 2019). The Safe and Sound 
Protocol (SSP) is a passive acoustic intervention that is designed as a “neural exercise” to promote 
efficient regulation of autonomic state. Prior research has shown that the SSP can improve autonomic 
function, auditory hypersensitivities, and emotion regulation in individuals with Autism Spectrum 
Disorders (Porges et al., 2013; 2014). Though used by some therapists as part of trauma therapy, there are 
currently no published studies to document its efficacy for PTSD symptoms or comorbidities. This 
current observational pilot study is being conducted to establish methods for an upcoming randomized 
controlled trial to test the utility of the SSP for trauma treatment.  
Study Procedures 
All participants, regardless of study arm, will be recruited from the pool of Spencer Psychology clients 
who are actively receiving psychotherapy. Participants will continue to receive weekly or bi-weekly 
psychotherapy during the course of the study. In both arms, participants complete surveys that assess 
PTSD symptoms (PCL-5), anxiety symptoms (GAD-7), and, autonomic symptoms (BPQ) over the course 
of 4 timepoints. 
 
 
Psychotherapy + SSP Arm 
After having received an email from the potential subject indicating interest in participation, 
subjects will be screened online via email to ensure they meet eligibility criteria for the study. If 
client meets eligibility criteria for study, they will be contacted by a research assistant to schedule 
their first visit prior to beginning the SSP. Participants will be given an option of either 
scheduling a session at an Indiana University laboratory building or at Spencer Psychology, 
where they receive therapy.  
When the participant arrives, they will complete a standard COVID-19 screener inside the 
entrance hallway. Masks will be worn by researcher and participant during the protocol as long as 
these are part of official state and university guidelines. Masks may be removed if research 
assistants and participant have proof of complete vaccination. If participant has symptoms or has 
been in contact with someone likely to have COVID-19, the visit will be rescheduled.  If 
participant passes the screening, they will be led to the laboratory.  
Visit 1. The researcher will describe the study, offer to read through the consent form with the 
participant or have the participant read the consent on their own, and answer any questions. If 
client consents, data collection will begin. 
The participant will complete a set of surveys self-reporting demographics, comorbidities, and 
psychological well being via Qualtrics on a laptop provided by the researcher (~15 minutes). The 
RA will then guide the participant through physiological data collection using the iom2 ear clip. 
Participants will be given instructions on how to put on the earlobe sensor, which attaches via an 

 
 
ear clip. To stabilize the iom2 cable, an additional clip may be used to attach the iom2 to clothing, 
waist, or it would be secured on a lab-provided shoulder holster. Once sensor is in place, a 
researcher will connect the iom2 device to a laptop and begin recording. 
The participant will then be cued by a video to move into 3 postures for 3 minutes each: lying 
down on a cot, sitting up, and standing. After the final posture, the participant will be instructed 
to remove the measurement device. The device, the cot, and the chair will be sterilized after use 
with soap and water or other cleaner. 
At completion of the first visit, participants will be provided the first $25 Amazon gift card and 
reminded of the incentive schedule. If the participant knows when their SSP administration will 
begin, they will be scheduled for their next visit which will take place 1 week after their final 
listening session. If start date is unknown, the participant will be contacted in 3 weeks about 
scheduling visit 2. 
SSP Sessions and Data Collection  
The Safe and Sound Protocol (SSP) will be delivered with 5 hours of increasing frequency 
modulation over time, as used in prior studies (Porges et al., 2013; 2014), using a phone-based 
app. Participants will have a choice of 2 music playlists, one that featured popular adult 
contemporary music and one that primarily featured music from children’s movies. Frequency 
filtering will be applied to playlists using the Safe and Sound Protocol (SSP) using an algorithm 
to alternate narrowing and expanding the range of acoustic frequencies over time, with the 
alternations intensifying in frequency range over the course of the music tracks. The filtering is 
optimized for the frequency response of adult human hearing and intended to mimic the 
expression of the human voice around a central set of frequencies of 800-1200 Hz. The results of 
the filtering method are similar to adjusting the treble and bass settings on a stereo system while 
music is playing; the melody and instruments can still be heard, but the highest and lowest pitches 
are modulated over time. Music listening will be conducted with high-fidelity, closed-back, over-
the-ear headphones while seated. The headphones had a flat frequency response to accurately 
reproduce music frequencies. The sessions will aim for 30 minutes of listening in each 1-hour 
session to permit opportunity to discuss client response, and support shifts that happen during 
listening. The 30 minutes of listening may be discontinuous, with client and therapist each having 
the possibility to stop the music at any point to discuss and may resume when client is ready. If 
agreed on by the participant and therapist, some listening time will be completed either at home 
or in a listening room provided by Spencer Psychology. The room is for those who do not have a 
distraction-free space and/or over-the-ear headphones at home 
Therapists will report on total listening minutes during the session and notes on client response 
into their standard session reporting form. Spencer Psychology will provide these portions of the 
session notes to the research team. Researchers will not have access to any additional therapist 
notes on the client. 
Visit 2. The week after the client completes their 5th hour of SSP, a second assessment will be 
scheduled. As part of this assessment, the client will complete the survey post assessment on the 
laptop (~10 minutes) and pulse data collection using the iom2 during supine, sitting, and standing 
postures. Upon completion, the participant will schedule their 4-week post appointment. They 
will then receive their second $25 Amazon gift card and be reminded of the incentive schedule. 
Visit 3. Five weeks after their final SSP session, participants will return for their last assessment. 
They will then complete the survey post assessment on the laptop (~10 minutes) and pulse data 

 
 
collection using the iom2 during a supine-sit-stand challenge using the same procedures as 
previous visits. They will then receive their third $25 Amazon gift card, and another $25 Amazon 
gift card if they’ve completed all three assessments. 
Data collection from Spencer Psychology medical records. 
The study team will receive medical records from Spencer Psychology. Spencer Psychology has a 
secure, internal database that Spencer Psychology staff will program to output required 
information. Unique study IDs will be assigned to participants and medical records will be 
exported and stored with these IDs, not with the names of the participants. We will collect the 
following information from medical records: Gender, Birth date, Intake and treatment 
information (date, diagnosis, therapy goals, medication use), session information during SSP 
administration information (length of use during session), mood and cognitive features during the 
visit, Changes in treatment objectives, goals, and diagnosis, Clinician comments on visit. 
 
Treatment as Usual (Psychotherapy Only) 
 
If they are interested in participation, they will contact the study team by email provided in the 
recruitment materials.The study team will send out a link to a screener survey that contains the 
PCL-5 post-traumatic stress questionnaire. The screener will be used to match this sample to the 
distribution of the PTSD symptom severity in the SSP study.  If eligible for the study based on 
the screener, the participant will receive an email invitation to participate in the full study, 
including a link to the survey which contains the Informed Consent Statement and the first full 
survey. 
 
Subjects will then complete the first survey, which will ask about demographic information; 
email address for follow up surveys; caffeine, alcohol, nicotine use; medication use; therapy 
history; PTSD, anxiety, and autonomic symptoms. The survey will close with a statement 
describing the timing of their next assessments when they will receive the email invitation to 
complete their next survey, who to contact if they do not receive that email, and that they will 
receive their digital gift card code via the email address they provided in the survey.  
 
After subjects have consented and completed the first survey, the study team will receive the 
following information from Spencer Psychology: gender, intake date, diagnosis, client therapy 
goals. The study team will also receive the following information from session notes for the 
duration of the study: mood and cognitive features during visits, changes in treatment objectives, 
goals, and diagnosis, clinician comments on visits. 
 
Questionnaires that assess PTSD symptoms, anxiety symptoms, and, autonomic symptoms will 
be used for measuring main outcomes. The timeline of surveys was based on average length of 
SSP listening completion from the SSP+Psychotherapy arm: 
1. 
Survey 1 (10-15 minutes) 
2. 
Survey 2 (5-10 minutes, 45 days after survey 1) 
3. 
Survey 3 (5-10 minutes, 45 days after survey 2) 
4. 
Survey 4 (5-10 minutes, 30 days after survey 3) 
  
 

 
 
Incentives 
Participants in the music listening group were compensated up to a total of $125: a $25 gift card for each 
lab visit and corresponding survey, and an additional $25 gift card for completing all the assessments. 
Participants in the treatment as usual group were compensated up to $50: a $10 gift card for each of the 4 
surveys they completed, with an additional $10 for completing all of the surveys. 
 
Statistical Plan 
The goal of the study is to collect exploratory pilot data to inform a large randomized study in the future. 
Due to the novel nature of the research question there is no prior data to inform power analysis. Results 
from this small study will be used for power estimates for the upcoming planned randomized study. All 
efforts will be made to avoid missing data. Research assistants will track potential reasons for missing 
data in order to strengthen procedures in the follow up study and reduce missing values. Quality 
assurance steps for data collection will include: Monthly meetings with RAs to visualize and review 
incoming data, automated range checks, and comparing redundant items that are included in both medical 
records and self-reports for convergence (e.g., age). Change over time will be modeled using mixed 
effects modeling with maximum likelihood, which uses all available data on predictors even when some 
values are missing. Support for non-zero parameters will be indicated by 95% confidence intervals 
excluding zero. In the SSP+psychotherapy group, earlobe pulse data will be used to quantify inter-beat 
intervals using automated peak detection with manual checks for accuracy. These will be analyzed for 
mean heart period and respiratory sinus arrhythmia using previously published methods (Porges, 1985; 
1986; Lewis et al., 2012). 
 
References 
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