Mindfulness involves an intentional regulation of attention to and awareness of the present moment, as well as non-judgmental acceptance of the ongoing flow of sensations, thoughts, and/or emotional states (Baer et al. 2006; Bishop et al. 2004). Commonly conceptualized as being comprised of several facets, mindfulness includes observing (i.e., tendency to notice or attend to internal and external experiences), describing (i.e., tendency to label internal and external experiences with words), acting with awareness (i.e., full awareness and undivided attention of current experiences), non-judging of experience (i.e., viewing internal experiences with a non-evaluative stance), and non-reactivity to inner experience (i.e., tendency to allow thoughts, emotions, and bodily sensations to come and go; Baer et al. 2006). Mindfulness is conceptualized as both a state, consisting of fluctuations in behaviors, thoughts, or emotions, and a trait, a relatively stable personality characteristic that is more long-lasting and less context-dependent (Baer et al. 2006; Brown and Ryan 2003; Lau et al. 2006). Regardless of one’s level of trait or state mindfulness, it is considered to be malleable via intervention (e.g., Branstrom et al. 2010; Kimbrough et al. 2010; King et al. 2013; Niles et al. 2012, 2013).

Recently, mindfulness has received increasing attention in the context of traumatic stress research due to its potential theoretical and clinical relevance to the etiology, maintenance, and treatment of posttraumatic stress disorder (PTSD; Kim et al. 2013; Vujanovic et al. 2011, 2016). High levels of mindfulness may serve as a protective factor in the context of trauma recovery (e.g., Thompson et al. 2011), while lower levels of mindfulness may confer risk following trauma exposure (Vujanovic et al. 2016). Mindfulness may help foster approach-oriented coping when individuals are triggered by external reminders of a traumatic event, and therefore, decrease attempts to avoid one’s internal emotional, cognitive, and physical experiences, otherwise known as experiential avoidance. Furthermore, individuals who are more aware of present experience may be better able to effectively engage in various forms of treatment (Vujanovic et al. 2016). Mindfulness-based interventions have shown promise in decreasing PTSD symptoms in a variety of populations (e.g., military veterans, community samples of women, cancer patients, survivors of intimate partner violence) (Banks et al. 2015). Therefore, it is important to build upon our understanding of the relations between the various facets of mindfulness and PTSD symptomatology across clinical populations to better inform mindfulness-based intervention efforts.

Across studies, mindfulness has been negatively associated with PTSD symptom severity; however, patterns of association between mindfulness facets and specific PTSD symptom clusters have been varied. In a sample of trauma-exposed undergraduates, the non-judging of experience facet of the Five Facet Mindfulness Questionnaire (FFMQ; Baer et al. 2006) was incrementally and negatively associated with PTSD avoidance symptom severity, after controlling for experiential avoidance (Thompson and Waltz 2010). In another sample of undergraduates (Kalill et al. 2014), incremental negative associations between the describing facet of the FFMQ and PTSD hyperarousal symptom severity were documented; the FFMQ non-reactivity to inner experience facet also was associated with overall PTSD symptom severity, as well as re-experiencing and hyperarousal symptom severity. Furthermore, Hanley et al. (2017) found non-judging of experience, observing, and acting with awareness facets to be significantly associated with lower levels of PTSD symptom severity in undergraduates.

In trauma-exposed community samples, significant negative associations between the acting with awareness and accepting without judgment scales of the Kentucky Inventory for Mindfulness Skills (KIMS; Baer et al. 2004) and PTSD symptom severity have been documented (Vujanovic et al. 2009). While the accepting without judgment subscale was significantly associated with each PTSD symptom cluster, the acting with awareness subscale was only negatively associated with the re-experiencing symptom cluster. Similarly, Bernstein et al. (2011) found mindful awareness and attention, indexed via the Mindful Awareness and Acceptance Scale (MAAS; Brown and Ryan 2003), to be negatively associated with PTSD symptom severity in a trauma-exposed community sample. In a more recent community sample, higher levels of mindfulness traits per the FFMQ were associated with lower levels of PTSD symptoms (Boughner et al. 2016). Furthermore, this study also found that describing, acting with awareness, and non-judging of experience partially mediated associations between lifetime and child trauma exposure and current PTSD symptom severity.

In military samples, mindfulness, as measured by the MAAS (Brown and Ryan 2003), was negatively associated with PTSD symptomatology in a sample of US war veterans (Dahm et al. 2015). However, other studies found no differences in levels of mindfulness between combat veterans with and without PTSD (Call et al. 2015; Wahbeh et al. 2011). In a sample of firefighters, trait mindfulness measured by the MAAS (Brown and Ryan 2003) was associated with lower levels of PTSD symptomatology, depressive symptoms, physical symptoms, and problems with alcohol use. In active-duty police officers, an inverse association between the KIMS accepting without judgment subscale and PTSD symptom clusters of avoidance and intrusion were documented (Chopko and Schwartz 2013). This study also established an inverse association between the describing and accepting without judgment subscales of the KIMS and the hyperarousal symptom cluster of PTSD (Chopko and Schwartz 2013).

Cross-sectional findings have been strengthened by clinical trials suggesting the potential efficacy of mindfulness-based interventions, including mindfulness-based stress reduction (MBSR), mindfulness-based cognitive therapy (MBCT), and mindfulness-based stretching and deep breathing, in reducing symptoms of PTSD. Randomized clinical trials on mindfulness-based interventions for PTSD have been conducted across varied populations, including patients with cancer (e.g., Branstrom et al. 2010), military veterans (e.g., Kearney et al. 2012; Niles et al. 2012), and community adults with PTSD (e.g., Kim et al. 2013). Across studies, mindfulness-based interventions generally have been compared to wait-list control conditions or “treatment-as-usual.” No randomized clinical trials have been conducted to date comparing mindfulness-based interventions directly with cognitive-behavioral therapies specifically for PTSD, such as cognitive processing therapy (Resick et al. 2008) or prolonged exposure therapy (Foa et al. 2007). One randomized controlled trial compared present-centered therapy, a non-trauma focused treatment for PTSD (Schnurr et al. 2003), to MBSR and found greater PTSD symptom reduction in the MBSR condition (Polusny et al. 2015). Another randomized controlled trial compared group cognitive-behavioral therapy with Mindfulness-Oriented Recovery Enhancement (MORE) in trauma-exposed, homeless men with co-occurring substance use and psychiatric conditions; and MORE was associated with greater reductions in PTSD symptoms as compared to group cognitive-behavioral therapy (Garland et al. 2016). In addition, changes in mindfulness have been documented in the context of residential PTSD treatment for military veterans, suggesting that mindfulness might also function as a mechanism of change in more established PTSD intervention programs (Boden et al. 2012; Owens et al. 2012). Although this literature remains in a nascent stage of development, the results remain promising (Banks et al. 2015; Lang 2017; Vujanovic et al. 2016).

Missing from the vast majority of work on mindfulness-PTSD relations to date is a focus on psychiatric inpatients. Several randomized controlled trials have found that mindfulness-based interventions have resulted in symptom and quality of life improvements for individuals with psychosis and schizophrenia (e.g., Aust and Bradshaw 2017). Other studies have found associations between mindfulness and other psychiatric outcomes, such as depression and anxiety, in psychiatric inpatient samples (e.g., Perich et al. 2013). Related research has been conducted with samples of veterans with PTSD in inpatient (Landrum 2016) and residential treatment programs (Boden et al. 2012; Owens et al. 2012). In addition to veteran samples, relations between mindfulness facets and PTSD symptoms have been examined in women in residential treatment programs for substance use (Price et al. 2012). However, no studies have been conducted to evaluate associations between mindfulness facets and PTSD symptomatology in psychiatric inpatients with varying levels of PTSD symptomatology. This is unfortunate since trauma exposure rates as high as 98% have been documented among psychiatric inpatients (e.g., Grubaugh et al. 2011; Mueser et al. 1998; Walsh et al. 2003). Furthermore, rates of PTSD in psychiatric populations vary between 19 and 43% (Grubaugh et al. 2011; Howgego et al. 2005; Mueser et al. 2015), significantly higher than those of the general population. Additionally, mindfulness and facets of mindfulness have been variably measured in the literature across populations. In the relevant literature, the FFMQ and KIMS have been used to measure the specific facets of mindfulness whereas the MAAS has been used to measure mindful attention. Although all instruments measuring mindfulness and its facets can yield clinical utility, a better understanding of the relations between mindfulness facets and PTSD symptoms in psychiatric inpatients is a necessary first step in informing future research and clinical interventions.

The current study aims to address these research issues by concurrently examining the main effects of mindfulness facets, as measured by the FFMQ, in association with PTSD symptom severity in a trauma-exposed, psychiatric inpatient sample. Taken together, acting with awareness, non-judging of inner experience, and non-reactivity to inner experience have demonstrated more robust associations with PTSD symptomatology across populations, as compared to the observing and describing facets of mindfulness (e.g., Thompson and Waltz 2010; Vujanovic et al. 2009; Chopko and Schwartz 2013). These findings may indicate that the ability to act with present-centered awareness, to remain non-evaluative of internal experiences, and to allow internal experiences to come and go may be more relevant to managing PTSD symptoms via decreasing avoidance than merely being able to pay attention to and label present experiences (Vujanovic et al. 2016). Notably, no published studies to date have examined relations between the various facets of mindfulness, defined by the FFMQ, and PTSD symptomatology as defined by the DSM-5; and no studies have examined these associations in psychiatric inpatients. Specifically, this study examines how the observing, describing, acting with awareness, non-judging of inner experience, and non-reactivity to inner experience subscales of the FFMQ are associated with PTSD symptom severity and severity of each PTSD symptom cluster (intrusions, avoidance, negative mood and cognition, and arousal; APA 2013) in psychiatric inpatients. Specifically, based upon extant literature and relevant theoretical models (Follette et al. 2006; Vujanovic et al. 2011, 2016), it was hypothesized that higher levels of acting with awareness, non-judging of inner experience, and non-reactivity to inner experience subscales would be most robustly associated with lower levels of PTSD symptom severity and the severity of each PTSD symptom cluster and vice versa. The observing and describing facets were not expected to be significantly associated with PTSD outcomes. These effects were expected after controlling for theoretically relevant covariates, including number of traumatic life events endorsed and number of psychiatric diagnoses on record. The covariates were selected based on their associations with PTSD symptomatology in psychiatric inpatient samples (e.g., Martin et al. 2017; Vujanovic et al. 2017a, b) and their inclusion in models examining mindfulness-PTSD relations (e.g., Vujanovic et al. 2009).

Method

Participants

The sample was comprised of 152 psychiatric inpatients (42.1% women; Mage = 33.86, SD = 11.29) at a public, university-affiliated, acute-care psychiatric inpatient hospital in a large metropolitan area in the southern USA. See Table 1 for sample characteristics. Eligible individuals were those 18–65 years of age who reported a history of trauma exposure consistent with Diagnostic and Statistical Manual of Mental Disorders—Fifth Edition (DSM-5; APA 2013) PTSD criterion A. Potential participants were deemed ineligible if they were unable to provide verbal and written informed consent or if they obtained a score below 20 on the Mini Mental Status Examination (see below).

Table 1 Participant characteristics
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Procedure

All individuals assigned to one unit in an acute-care psychiatric inpatient hospital were screened for a history of exposure to trauma using the LEC-5 within 24 h of admission. Within 5 days of admission, study staff approached individuals endorsing at least one trauma for potential participation. Individuals who were willing to participate provided informed verbal and written consent. Participants were then administered the MMSE and completed a self-report packet, which included the questionnaires used for the current study. Participation was completely voluntary; no financial compensation was provided. The study was approved by the institutional review boards at the University of Texas Health Science Center at Houston and the University of Houston.

Measures

Mini Mental Status Examination (MMSE; Folstein et al. 1975; Tombaugh and McIntyre 1992)

The MMSE is an 11-item instrument used as an objective screening tool for general mental status. It provides brief assessment of abilities in the areas of attention, memory orientation (e.g., recall of words, recognition of sentences), and initiation and maintenance of verbal and motor responses. Scores range from 0 to 30, with scores below 20 indicating moderate cognitive impairment.

Medical Records Review

Demographic information, including age, sex, race/ethnicity, and psychiatric diagnoses were derived from electronic medical records. Psychiatric diagnoses were determined via non-standardized clinical interviews conducted by unit psychiatrists. Discharge psychiatric diagnoses were used to inform the diagnostic composition of the present sample. Since patients commonly present for admission in acute distress, intake diagnostic information is often incomplete; thus, discharge diagnostic information is more comprehensive and provides a standardized time-point for extraction of diagnostic data. The number of psychiatric diagnoses was entered as a covariate in the hierarchical regression analyses. A summary of the diagnostic composition of the sample is reported in Table 1.

Life Events Checklist for DSM-5 (LEC-5; Weathers et al. 2013)

The LEC-5 is a self-report measure used to screen for potentially traumatic events experienced anytime during the lifespan. Respondents are presented with 17 potentially traumatic events (e.g., natural disaster, combat, sexual assault), including an additional item assessing any “other” traumatic events not listed. In the current study, respondents were asked to indicate whether each listed event “has happened to you at some point in your life.” This represents a modification of the original LEC-5, which asks participants whether each event (a) “happened to you,” (b) “you witnessed it happen to someone else,” (c) “you learned about it happening to a close family member of close friend,” (d) “you were exposed to it as part of your job,” and/or (e) “you’re not sure if it fits.” Another modification included the removal of two items from the LEC-5 (exposure to toxic substance and severe human suffering) and the addition of two items (childhood physical abuse and childhood sexual abuse). These modifications were instituted to reduce the potential for false-positive reports (e.g., endorsement of ‘exposure to toxic substance’ by patients with psychotic-spectrum psychopathology) and to add a childhood time-frame for endorsement of sexual or physical abuse/assault. In the current study, the LEC-5 was used to characterize trauma exposure among the sample and to determine the number of potentially traumatic events each participant experienced, which was entered as a covariate in the hierarchical regression analyses.

PTSD Checklist-Civilian Version-5 (PCL-5; Blevins et al. 2015)

The PCL-5 is a 20-item self-report measure of PTSD symptom severity. Each of the 20 items reflects a DSM-5 symptom of PTSD (APA 2013). Respondents are asked to rate each item on a five-point scale (0 = Not at all to 4 = Extremely) in terms of how often they have been bothered by the symptom in the past month (e.g., “In the past month, how much have you been bothered by repeated, disturbing, and unwanted memories of the stressful experience?”). Total symptom severity scores range from 0 to 80, where higher scores indicate higher symptom severity. A preliminary PTSD cut-off score of 33 is recommended in the current literature (Bovin et al. 2016). The PCL-5 has demonstrated good internal consistency, test-retest reliability, and convergent and discriminant validity (Armour et al. 2015; Bovin et al. 2016). The internal consistency of the PCL-5-total score in the current study was very good (Cronbach’s α = 0.91); internal consistencies for each of the subscales were also good (intrusions: Cronbach’s α = 0.62; avoidance: Cronbach’s α = 0.73; negative alterations in cognitions and mood: Cronbach’s α = .89; arousal: Cronbach’s α = 0.83). The PCL-5 was used to determine PTSD symptom severity as well as severity of each of the four DSM-5 (APA 2013) PTSD symptom clusters; these five variables were outcomes in the present study.

Five Facet Mindfulness Questionnaire (FFMQ; Baer et al. 2006)

The FFMQ is a 39-item measure of mindfulness. Items are rated on a five-point Likert-type scale ranging from 1 (never or very rarely true) to 5 (very often or always true). The FFMQ measures five facets of mindfulness including observing, describing, acting with awareness, non-judging of experience, and non-reactivity to inner experience (Baer et al. 2006). The observing subscale gauges respondents’ attention to internal and external experiences (e.g., “When I’m walking, I deliberately notice the sensations of my body moving”); the describing subscale gauges respondents’ ability to label internal experiences (e.g., “I am good at finding words to describe my feelings”); the acting with awareness subscale gauges respondents’ attention to activities in the moment (e.g., “When I do things, my mind wanders off and I’m easily distracted”); the non-judging of experience subscale gauges respondents’ ability to remain non-evaluative about their internal experiences (e.g., “I criticize myself for having irrational or inappropriate emotions”); the non-reactivity to inner experience subscale gauges respondents’ ability to allow internal experiences to come and go (e.g., “I perceive my feelings and emotions without having to react to them”) (Baer et al. 2006). The FFMQ has good construct validity and reliability (Baer et al. 2008), and the internal consistency of the FFMQ in the current study was good (Cronbach’s α = 0.83). Internal consistencies of all subscales were also good (i.e., observing: α = .83, describing: α = 0.53, acting with awareness: α = 0.86, non-judging of experience: α = 0.77, non-reactivity to inner experience: α = 0.77).

Data Analyses

Analyses were conducted in IBM SPSS Statistics 22. A series of five hierarchical regression analyses were performed. Criterion variables included: (1) PCL-5-total score, (2) PCL-5-intrusion symptoms subscale score, (3) PCL-5-avoidance symptoms subscale score, (4) PCL-5-negative alterations in cognitions and mood symptoms subscale score, and (5) PCL-5-arousal symptoms subscale score. At step one of each of the models, the number of psychiatric diagnoses and LEC-5-total number of traumatic events were entered as covariates. At step two of each of the models, the five FFMQ subscales (i.e., FFMQ-observing, FFMQ-describing, FFMQ-acting with awareness, and FFMQ-non-judging of experience, FFMQ-non-reactivity to Inner experience) were entered concurrently to examine the unique incremental contributions of these mindfulness variables in relation to each of the PTSD-relevant symptom outcomes.

Results

See Table 2 for a summary of descriptive statistics and correlations among study variables. Assumptions of normality were met. Participants reported an average of 6.06 potentially traumatic events on the LEC-5 (SD = 3.62) and endorsed an average PCL-5-total score above the suggested cut-off of 33 (Bovin et al. 2016) for a probable PTSD diagnosis (M = 59.48, SD = 21.79). Based on the recommended cut-off, 76.3% of the sample met criteria for a probable PTSD diagnosis. Participants were diagnosed with an average of two current psychiatric diagnoses (SD = 1.14).

Table 2 Correlations and descriptive statistics among study variables
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In terms of bivariate correlations, the total number of traumatic event types experienced (LEC-Total) was significantly positively correlated with the PCL-5-total score, as well as with the four PTSD symptom cluster severity scores per the PCL-5. However, number of psychiatric diagnoses was not significantly correlated with any of the study variables. The FFMQ-observing subscale was significantly positively correlated with the LEC-total score as well as the PTSD intrusion subscale. The FFMQ-describing subscale was significantly positively correlated with the PCL-5-intrusion subscale and negatively correlated with PTSD symptom severity subscales of negative alterations in cognitions and mood and arousal. The FFMQ-acting with awareness subscale was significantly negatively correlated with total number of adult traumatic events experienced and significantly negatively correlated with the PCL-total score and three of the four PTSD symptom severity clusters (intrusions, negative alterations in cognitions and mood, arousal). Similarly, the FFMQ-non-judging of experience subscale was significantly negatively correlated with total number of adult traumatic events experienced, as well as three of the four PTSD symptom severity clusters (intrusion, negative alterations in cognitions and mood, arousaL). Lastly, the FFMQ-non-reactivity to inner experience subscale was only significantly negatively correlated with PCL-total score and the PCL- negative alterations in cognitions and mood and PCL-intrusion subscales.

Please see Table 3 for a summary of hierarchical regression analyses. With regard to PTSD symptom severity (PCL-Total score), step one contributed 20.2% of variance to the model (p < 0.001), and number of traumatic life events was a significant correlate. Step two contributed 26.8% of unique variance to the model (p < 0.001). Acting with awareness, non-judging of inner experience, and non-reactivity of inner experience were all significant incremental correlates of PTSD symptom severity (p’s < 0.05), above and beyond covariates at step one.

Table 3 Hierarchical regression analyses: incremental associations between mindfulness facets and posttraumatic stress symptom severity
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In terms of PTSD-intrusion symptom severity, step one contributed 10% of variance to the model (p = 0.002), and number of traumatic life events was a significant correlate. Step two contributed 33.2% of unique variance to the model (p < 0.001), and describing, acting with awareness, non-judging of experience, and non-reactivity to inner experience were significant incremental correlates (p’s < 0.05), above and beyond covariates at step one.

With regard to PTSD-avoidance symptom severity, step one accounted for 13.2% of variance to the model (p < 0.001), and number of traumatic life evens was a significant correlate (p < 0.001). Step two did not significantly contribute unique variance to the model, and none of the five mindfulness facets were significant correlates of PTSD-avoidance symptoms.

In terms of PTSD-negative alterations in cognitions and mood symptom severity, step one contributed 20.2% of variance to the model (p < 0.001), and number of traumatic life events was a significant correlate. Step two accounted for 25.9% of unique variance to the model (p < 0.001). Acting with awareness, non-judging of experience, and non-reactivity to inner experience were significant incremental correlates (p’s < 0.05), above and beyond covariates at step one.

With regard to PTSD-arousal symptom severity, step one explained 18% of variance (p < 0.001), and number of traumatic life events was a significant correlate. Step two accounted for 23.8% of unique variance in the model, and acting with awareness was a significant incremental correlate (p < 0.001), above and beyond covariates at step one.

Discussion

The present study sought to address the associations between facets of mindfulness, as measured by the Five Facet Mindfulness Questionnaire (FFMQ; Baer et al. 2006), and PTSD symptomatology in an acute-care psychiatric inpatient sample. Consistent with hypotheses, acting with awareness, non-judging of experience, and non-reactivity to inner experience demonstrated significant, incremental negative associations with total PTSD symptom severity, above and beyond variance contributed by number of traumatic life events and number of psychiatric diagnoses at discharge. These findings are consistent with literature on associations between these FFMQ facets and overall PTSD symptom severity in other trauma-exposed samples (e.g., Kalill et al. 2014; Vujanovic et al. 2009; Hanley et al. 2017). Thus, psychiatric inpatients with heightened present-centered awareness as well as non-judgmental acceptance of and non-reactivity to present experience were less likely to report high levels of PTSD symptoms, and vice versa. These results lend further support to the potential clinical significance of mindfulness facets with regard to PTSD symptoms among acute-care psychiatric populations. Inconsistent with hypotheses, the observing and describing facets were not significantly associated with PTSD symptom severity. This is inconsistent with past work among veterans, which demonstrated negative associations between the observing and describing facets of the FFMQ and global PTSD symptom severity (Stephenson et al. 2017). Alternatively, the present findings partially support those found in trauma-exposed community samples and treatment-seeking PTSD samples, wherein the observing facet of the FFMQ was not significantly associated with PTSD symptomatology (Boughner et al. 2016; Schoorl et al. 2015). Additionally, the describing facet of the FFMQ has not shown significant associations with overall PTSD symptomatology (Possemato et al. 2016; Stephenson et al. 2017); however, it has been examined as a mediator of the relationship between past trauma and current PTSD symptoms (Boughner et al. 2016). Inconsistencies in findings across populations underscore the need for intervention-based studies and longitudinal designs to conclusively determine the most relevant mindfulness skills with regard to PTSD symptomatology.

Describing demonstrated positive associations with the PTSD intrusion cluster, while acting with awareness, non-judging of experience, and non-reactivity to inner experience demonstrated significant negative associations, above and beyond effects of covariates. Specifically, higher levels of labeling internal and external experiences with words were associated with heightened intrusion symptom severity and vice versa. As such, individuals with increased describing skills may manifest more focused attention on their internal experiences, including trauma-related intrusions, thus amplifying the extent to which such symptoms are reported. Conversely, higher levels of acting with awareness, non-judging of experience, and non-reactivity to inner experience were associated with lower levels of intrusion symptom severity and vice versa. These findings are consistent with the prior literature (e.g., Kalill et al. 2014; Vujanovic et al. 2009). Inconsistent with hypotheses, the observing facet of the FFMQ was not significantly associated with intrusion symptoms. This finding resembles those in trauma-exposed adults, wherein none of the FFMQ subscales, including observing, were significantly associated with the intrusion symptom cluster (Gonzalez et al. 2016). The tendency to notice internal and external experiences may not be especially relevant to PTSD symptomatology, in the absence of skills relevant to awareness, non-judgmental acceptance, or non-reactivity to that experience.

Acting with awareness, non-judging of experience, and non-reactivity to inner experience demonstrated significant incremental associations with negative alterations in cognitions and mood symptom severity, above and beyond covariates. Heightened levels of these facets of the FFMQ were associated with lower levels of negative alterations in cognition and mood, and vice versa. In veteran samples, increased mindfulness has been associated with decreased levels of emotional numbing (Stephenson et al. 2017), which aligns with the negative cognition and mood symptom cluster of the PCL-5. Inconsistent with hypotheses, the observing and describing facets of the FFMQ were not significantly associated with the negative cognition and mood symptom cluster; however, the describing facet was significantly associated with the negative cognition and mood cluster at the bivariate level (r = − 0.30, p < 0.01). This is partially consistent with recent work, which also failed to document significant associations between observing and the DSM-5 PTSD symptom cluster of negative alterations in cognitions and mood, in a sample of trauma-exposed adults (Boughner et al. 2016). Therefore, observing and describing thoughts and emotions may not be as strongly associated with this symptom cluster as actively tolerating and accepting internal experiences.

With regard to arousal symptom severity, acting with awareness manifested significant negative associations, above and beyond covariates. Higher levels of acting with awareness were significantly associated with lower levels of arousal symptoms, and vice versa. This is consistent with studies examining mindfulness and the hyperarousal symptoms of PTSD (e.g., Boughner et al. 2016; Gonzalez et al. 2016; Stephenson et al. 2017). Inconsistent with hypotheses and extant literature (e.g., Chopko and Schwartz 2013; Kalill et al. 2014), none of the other FFMQ facets were significantly associated with arousal symptomatology. Notably, describing (r = − 0.26, p < .01), non-judging of experience (r = − 0.39, p < 0.01), and non-reactivity to inner experience (r = − 0.22, p < 0.05) were all significantly associated with PTSD arousal symptom cluster severity at the bivariate level. These significant associations likely became non-significant once entered into the model with variables that accounted for more variance (e.g., acting with awareness). Perhaps becoming more aware of one’s inner experiences leads to present-focused behavior and decreased arousal symptoms (e.g., easily startled) (Delizonna et al. 2009). Similar to other PTSD outcomes, the observing facet was not significantly associated with the arousal symptom cluster at the bivariate or multivariate level. This is consistent with some other literature in trauma-exposed populations wherein observing was the only facet of mindfulness not significantly associated with PTSD symptomatology (e.g., Schoorl et al. 2015) but inconsistent with other studies (Stephenson et al. 2017).

Notably, no significant associations were found between any of the FFMQ facets and avoidance symptom cluster severity. This is inconsistent with the extant literature, as other studies have demonstrated significant associations among mindfulness facets and avoidance symptoms. Specifically, the non-judging of experience subscale of the FFMQ has been significantly associated with avoidance in samples of trauma-exposed undergraduate students (Thompson and Waltz 2010) and police officers (Chopko and Schwartz 2013), while the acting with awareness subscale of the FFMQ was significantly associated with PTSD avoidance symptoms in trauma-exposed adults with HIV/AIDS (Gonzalez et al. 2016). In a sample of veterans, non-reactivity to inner experience of the FFMQ was the only subscale significantly associated with the avoidance cluster of PTSD (Stephenson et al. 2017). These inconsistent findings may point to differences in associations between mindfulness facets and avoidance symptoms across populations.

Consistent with past literature, number of trauma exposure types, as measured by the LEC-5, was significantly and positively associated with PTSD symptom severity and severity of each of the PTSD symptom clusters (e.g., Brown et al. 2016; Lee et al. 2015; Maheux and Price 2015; Weiss et al. 2013; Zuromski et al. 2014). Indeed, individuals in the current study endorsed multiple traumatic life events (M = 5.98, SD = 3.55), as consistent with extant literature on inpatient samples (Mauritz et al. 2013; Barton et al. 2006; Melartin et al. 2002). Second, inconsistent with prior literature on complex psychopathology and increased severity of psychiatric symptoms (e.g., Arsenault-Lapierre et al. 2004; Krysinska and Lester 2010), number of psychiatric diagnoses was not significantly associated with any of the PTSD outcomes. This finding may be due to limitations inherent in the methodology since psychiatric diagnoses were derived via unstructured clinical interviews between psychiatrists and patients during daily interactions. These interviews often reflected queries relevant to current “presenting problems” and are likely an underestimate of the comprehensive psychiatric composition of the sample. Third, this sample reported a low mean monthly income (M = $350.07, SD = $1459.80) and was racially/ethnically diverse (i.e., 44.1% White/Caucasian, 37.5% Black/African American, 15.8% Hispanic), underscoring the urban, inner-city nature of the overall sample. Research incorporating more detailed socioeconomic and sociocultural information (e.g., perceived discrimination, cultural resilience) is needed to better understand the relevant impact on associations between mindfulness and PTSD symptoms. High levels of day-to-day stress experienced by socioeconomically disadvantaged individuals, due to lack of access to resources, greater exposure to neighborhood stress and violence, and/or societal discrimination, may negatively impact state levels of mindfulness (e.g., Vujanovic et al. 2017a).

Limitations and Future Research Directions

Several limitations of the present study should be noted. First, although a significant strength of the sample was its diversity with regard to psychiatric composition, race/ethnicity, and educational attainment, the sample was significantly socioeconomically disadvantaged, potentially compromising the external validity. Nonetheless, the low-income, inner-city nature of the sample represents a traditionally understudied population; thus, this study offers meaningful contribution to the literature in that regard. Second, the study relied almost exclusively on self-report measures, potentially contributing to method variance. Future research might include more clinical interview-based measures, specifically with regard to PTSD symptom severity and psychiatric diagnoses more generally, and utilize longitudinal or experimental designs. Notably, the current study used only one measure of mindfulness (i.e., FFMQ), which was selected due to its ability to measure various facets of mindfulness and its well-established use in the mindfulness-PTSD literature (e.g., Vujanovic et al. 2016). Future research should use other self-report measures of mindfulness to replicate and extend current findings. Also, it will be important for future research to examine the feasibility and effectiveness of mindfulness-based interventions delivered in acute-care psychiatric inpatient settings, on PTSD, related symptoms, and functional impairment. Third, the study employed a cross-sectional design, ruling out any potential conclusions about directionality among the study variables. Future studies might incorporate longitudinal designs to examine the predictive utility of state or trait mindfulness at admission with regard to treatment outcome or response during hospitalization. Fourth, medical records were utilized to inform the psychiatric diagnostic composition of the sample, and non-standardized assessments of psychiatric diagnoses were employed therefore limiting a comprehensive diagnostic picture of the sample. For example, it seems that PTSD was underdiagnosed in this setting, as only 2.0% of patients received a PTSD diagnosis by discharge, whereas 76.3% met criteria for PTSD per the PCL-5 diagnostic cut-off of 33 (Bovin et al. 2016).

This study investigated associations between the facets of mindfulness and PTSD symptom severity in acute-care psychiatric inpatients. Several FFMQ facets were associated with the PTSD intrusion, negative mood and cognition, and arousal symptom clusters, whereas there were no significant findings related to the avoidance symptom cluster. This work highlights the importance of examining the potential clinical utility of mindfulness-based interventions for trauma-exposed psychiatric inpatients with varying levels of PTSD symptom severity. Further research is warranted to gain a more complex understanding of these associations, using experimental and longitudinal designs.