Participants randomized to the MBCT intervention completed an open-ended, follow-up questionnaire designed to assess feelings and changes experienced from participation in the intervention. Participants were asked "Have you noticed any changes in how you experience emotions or handle stressful situations?". Responses were given in text form rather than on a pre-set scale, and were then categorized as positive change, no change, or negative change.

Skin conductance (SC) response was measured among participants receiving the in-person intervention using a mobile SC device, eSense (Mindfield Biosystems). Continuous recording of SC is measured with electrodes on hands and data is transmitted through the eSense app. Using the PhenX Toolkit protocol, a two minute baseline measure of SC will be obtained and then SC levels were measured during administration of the Standardized Trauma Interview immediately following to determine physiological reactivity to trauma stimuli. SC response is calculated by subtracting SC level at the end of baseline recording (average of last 30 seconds) from the maximum SC level value during the trauma interview.

The Patient Health Questionnaire-9 (PHQ-9) will assess for presence of depressive symptoms and serve as a major depressive disorder (MDD) screening tool. The PHQ-9 is a 9-item tool that asks respondents to indicate how frequently they have felt symptoms of depression on a scale of 0 to 3 where 0 = not at all and 3 = nearly every day. Total scores range from 0 to 27, where higher scores indicate worse depression.

The PCL-5 is a 20-item questionnaire asking respondents to report how much they have been bothered by problems in the past month on a scale of 0 (not at all) to 4 (extremely). Total scores range from 0 to 80 where higher scores indicate increased difficulty with responses to stressful experiences.

The BDI-II is a 21-item instrument asking respondents to indicate how much they are bothered by negative feelings. Responses are on a scale of 0 to 3 where 0 = the problematic feeling is not present and 3 = the feeling is very strong. Total scores range from 0 to 63, where high scores indicate worse problems with negative feelings.

The Clinician Administered PTSD Scale is a semi-structured interview used for diagnosing PTSD. The number of participants diagnosed with PTSD pre- and post-intervention will be compared between study arms.

The Mini International Neuropsychiatric Interview (MINI) is a semi-structured interview used for diagnosing MDD. The number of participants diagnosed with MDD pre- and post-intervention will be compared between study arms.

The Five Facet Mindfulness Questionnaire is a 39-item instrument assessing mindfulness, and includes five facets (observing, describing, acting with awareness, non-judging of inner experience, and non-reactivity to inner experience). Participants respond to each item on a scale of 1 to 5 where 1 = the statement is never or very rarely true for them and 5 = the statement is very often or always true. Total raw scores range from 39 to 195; certain items are reverse scored so that higher scores indicate increased mindfulness.

The Self Compassion Scale is a 12-item instrument assessing how respondents typically act towards themselves during difficult times. Items are answered on a scale of 1 to 5 where 1 = almost never and 5 = almost always. Total scores range from 12 to 60; certain items are reversed scored so that higher scores indicate increased self compassion.

Participants randomized to receive Mindfulness-Based Cognitive Therapy (MBCT) for 8 weeks. Participants enrolled after recruitment re-opened in September 2020 received the intervention virtually.

Participants randomized to the wait-list control study arm were administered the study assessments while not receiving active treatment. Participants were given the opportunity to participate in the MBCT intervention following completion of the study assessments. Participants enrolled after recruitment re-opened in September 2020 received the intervention virtually.

Total of all reporting groups

One participant in the In-Person Mindfulness-Based Cognitive Therapy study arm asked for their study data to be destroyed when they withdrew from the study.

Feasibility and acceptability of the Mindfulness-Based Cognitive Therapy intervention was assessed using the Client Satisfaction Questionnaire (CSQ). The CSQ is an 8-item questionnaire asking respondents to rate the quality of care they received on a scale from 1 to 4 where 1 = poor and 4 = excellent. Total raw scores range from 8 to 32 where higher values indicate greater satisfaction.

This analysis includes participants in the MBCT study arm who completed the Post-Intervention Assessment (25 participants) and who completed this questionnaire. Three participants had missing CSQ data due to an error where the questionnaire was not administered at this time-point.

Barriers to treatment was assessed using the Perceived Barriers to Psychological Treatment (PBPT) scale. The PBPT is a 25-item scale asking respondents about factors that interfere with attending weekly therapy. Items are rated on a 5-point scale where 1 = impossible to attend and 5 = not a problem. Total raw scores range from 25 to 125 where higher scores indicate low barriers regarding attending psychotherapy.

This analysis includes participants who completed the post-intervention assessment. Two participants in the Wait-list Control Group do not have data for the PBPT due to an error in not administering the instrument.

The Difficulties in Emotion Regulation Scale (DERS) is a 36-item instrument assessing emotion dysregulation and includes six subscales (non-acceptance of emotions, difficulty with goal-directed behavior in the presence of negative emotions, difficulty controlling impulses in the presence of negative emotions, lack of awareness of emotions, limited use of effective emotion regulation strategies, and lack of understanding of emotions). Responses are scaled from 1 (almost never) to 5 (almost always). Total raw scores range from 36 to 180; certain items are reverse scored so that higher scores indicate increased difficulty with emotion regulation.

One participant in MBCT requested all data removed so baseline score was unavailable; 1 participant in MBCT and 2 participants in Wait-list Control (WLC) had multiple missing self-report measures at baseline due to interviewer error. Missing data at Weeks 3, 5, and 7 were related to a participant not present at group or unable to be reached for the assessment component. The DERS was not administered to the WLC group at Weeks 3 and 7.

Participants randomized to the MBCT intervention completed an open-ended, follow-up questionnaire designed to assess feelings and changes experienced from participation in the intervention. Participants were asked "Have you noticed any changes in how you experience emotions or handle stressful situations?". Responses were given in text form rather than on a pre-set scale, and were then categorized as positive change, no change, or negative change.

This analysis includes participants receiving the MBCT intervention, either in-person or virtually, who attended the post-intervention assessment and responded to this question.

Skin conductance (SC) response was measured among participants receiving the in-person intervention using a mobile SC device, eSense (Mindfield Biosystems). Continuous recording of SC is measured with electrodes on hands and data is transmitted through the eSense app. Using the PhenX Toolkit protocol, a two minute baseline measure of SC will be obtained and then SC levels were measured during administration of the Standardized Trauma Interview immediately following to determine physiological reactivity to trauma stimuli. SC response is calculated by subtracting SC level at the end of baseline recording (average of last 30 seconds) from the maximum SC level value during the trauma interview.

8 MBCT and 8 WLC participants do not have usable baseline data due to a missing measurement, noise/error in output, iPad malfunction, or request for data removal. 2 MBCT participants and 7 WLC participants do not have Week 8 data because it was unusable due to noise/error in output. 3 MBCT participants and 1 WLC participants missed SC data collection at Week 8 due to onset of the COVID-19 pandemic and 2 WLC participants were missing SC data collection at Week 8 due to iPad malfunction.

The Primary Care PTSD Screen (PC-PTSD) is a 5-item screen designed for use in primary care used to assess for presence of PTSD symptoms and serve as PTSD screener. Respondents answer "yes" or "no" to each question and an individual is considered to have PTSD if they respond with "yes" to at least 3 of the 5 questions.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable. Additional missing data at Week 8 and Follow-up were due to interviewer error in not asking all the self-report questions or if a participant ran out of time and ended the assessment early and was unable to be reached at a later time to finish the assessment battery.

The Patient Health Questionnaire-9 (PHQ-9) will assess for presence of depressive symptoms and serve as a major depressive disorder (MDD) screening tool. The PHQ-9 is a 9-item tool that asks respondents to indicate how frequently they have felt symptoms of depression on a scale of 0 to 3 where 0 = not at all and 3 = nearly every day. Total scores range from 0 to 27, where higher scores indicate worse depression.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable. Additional missing data at Week 8 and Follow-up were due to interviewer error in not asking all the self-report questions or if a participant ran out of time and ended the assessment early and was unable to be reached at a later time to finish the assessment battery.

The PCL-5 is a 20-item questionnaire asking respondents to report how much they have been bothered by problems in the past month on a scale of 0 (not at all) to 4 (extremely). Total scores range from 0 to 80 where higher scores indicate increased difficulty with responses to stressful experiences.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable. Baseline data for 1 MBCT participant and 1 WLC participant was missing due to interviewer error. Additional missing data at Week 8 and Follow-up were due to interviewer error in not asking all the self-report questions or if a participant ran out of time and ended the assessment early and was unable to be reached at a later time to finish the assessment battery.

The BDI-II is a 21-item instrument asking respondents to indicate how much they are bothered by negative feelings. Responses are on a scale of 0 to 3 where 0 = the problematic feeling is not present and 3 = the feeling is very strong. Total scores range from 0 to 63, where high scores indicate worse problems with negative feelings.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable. Baseline data for 3 MBCT participants were also missing due to interviewer error. Additional missing data at Week 8 were due to interviewer error in not asking all the self-report questions or if a participant ran out of time and ended the assessment early and was unable to be reached at a later time to finish the assessment battery.

The Clinician Administered PTSD Scale is a semi-structured interview used for diagnosing PTSD. The number of participants diagnosed with PTSD pre- and post-intervention will be compared between study arms.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable.

The Mini International Neuropsychiatric Interview (MINI) is a semi-structured interview used for diagnosing MDD. The number of participants diagnosed with MDD pre- and post-intervention will be compared between study arms.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable.

The Five Facet Mindfulness Questionnaire is a 39-item instrument assessing mindfulness, and includes five facets (observing, describing, acting with awareness, non-judging of inner experience, and non-reactivity to inner experience). Participants respond to each item on a scale of 1 to 5 where 1 = the statement is never or very rarely true for them and 5 = the statement is very often or always true. Total raw scores range from 39 to 195; certain items are reverse scored so that higher scores indicate increased mindfulness.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable. Additional missing data at Baseline, and Week 8 were due to interviewer error in not asking all the self-report questions or if a participant ran out of time and ended the assessment early and was unable to be reached at a later time to finish the assessment battery.

The Self Compassion Scale is a 12-item instrument assessing how respondents typically act towards themselves during difficult times. Items are answered on a scale of 1 to 5 where 1 = almost never and 5 = almost always. Total scores range from 12 to 60; certain items are reversed scored so that higher scores indicate increased self compassion.

1 participant in the MBCT condition requested all data removed so baseline score was unavailable. Additional missing data at Baseline, Week 8 and Follow-up were due to interviewer error in not asking all the self-report questions or if a participant ran out of time and ended the assessment early and was unable to be reached at a later time to finish the assessment battery.

Participants randomized to the wait-list control study arm were administered the study assessments while not receiving active treatment. Participants were given the opportunity to participate in the MBCT intervention following completion of the study assessments.