Mediating Effect of Psychological Inflexibility, Insomnia, and Resilience on the Association Between Pain and Depression Among Patients With Chronic Pain

Hussein Makhour; Seockhoon Chung

doi:10.30773/pi.2025.0065

Psychiatry Investig > Volume 22(7); 2025 > Article

Makhour and Chung: Mediating Effect of Psychological Inflexibility, Insomnia, and Resilience on the Association Between Pain and Depression Among Patients With Chronic Pain

Original Article

Psychiatry Investigation 2025;22(7):806-812.

Published online: July 10, 2025

DOI: https://doi.org/10.30773/pi.2025.0065

Mediating Effect of Psychological Inflexibility, Insomnia, and Resilience on the Association Between Pain and Depression Among Patients With Chronic Pain

Hussein Makhour¹

, Seockhoon Chung^2,³

¹Faculty of Medical Sciences, Lebanese University, Beirut, Lebanon

²Department of Psychiatry, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea

³Life Care Center for Cancer Patient, Asan Medical Center Cancer Institute, Asan Medical Center, Seoul, Republic of Korea

Correspondence: Seockhoon Chung, MD, PhD Department of Psychiatry, Asan Medical Center, University of Ulsan College of Medicine, 86 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Republic of Korea Tel: +82-2-3010-3411, Fax: +82-2-485-8381, E-mail: schung@amc.seoul.kr

Received February 18, 2025 Revised April 22, 2025 Accepted May 12, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective

Chronic pain, impacting roughly 20% of the population, significantly affects quality of life and productivity. This study explored the mediating effects of psychological inflexibility, insomnia, and resilience on the association between pain and depression in patients with chronic pain.

Methods

Data on demographics, pain characteristics, and psychological factors were obtained through an online survey involving 100 patients from the Asan Medical Center Pain Clinic. Measures included the Patient Health Questionnaire-9, Insomnia Severity Index (ISI), Acceptance and Action Questionnaire-II (AAQ-II), and Brief Resilience Scale (BRS). Statistical analyses involved correlation, linear regression, and mediation analyses.

Results

A linear regression analysis revealed that the severity of depression was predicted by pain severity (β=0.18, p=0.018), ISI (β=0.22, p=0.010), AAQ-II (β=0.32, p<0.001), and BRS (β=-0.28, p=0.002). The mediation analysis showed that pain severity directly influenced depression severity. This relationship was partially mediated by ISI, AAQ-II, and BRS.

Conclusion

This study underscores the necessity for holistic approaches in chronic pain management that address the mediating effect of psychological factors. Targeted interventions focusing on insomnia, psychological inflexibility, and resilience can significantly enhance mental health outcomes for patients with chronic pain.

Keywords: Chronic pain, Resilience, Insomnia, Depression, Psychological inflexibility

INTRODUCTION

Chronic pain is a “distressing experience associated with actual or potential tissue damage with sensory, emotional, cognitive, and social components.” [1] This includes a specific time criterion for persistence, which typically lasts for three to 6 months [2]. This is a prevalent public health concern as it affects 20% of the general population and significantly impacts an individual’s quality of life and productivity [3].

A bidirectional association between pain and sleep has been observed [4]. Reducing pain severity might be helpful to reduce pain-related insomnia, while treating sleep disturbance might be beneficial to reduce pain severity [5,6]. Most individuals with chronic pain are also susceptible to developing anxiety and depression [7]. The persistent stress associated with chronic pain can lead to various emotional challenges, including altered mood, anger, chronic anxiety, confused thinking, social isolation, and weight fluctuations. It often results in significant losses, such as decreased exercise, disrupted sleep, strained social networks, impaired relationships, and employment and income loss. This may contribute to depression, particularly for those vulnerable to clinical depression. According to the American Pain Foundation, approximately 32 million people in the United States reported experiencing pain lasting more than a year. A quarter to more than half of these people simultaneously demonstrated symptoms of depression, which underscores the association between psychological status and chronic pain.

Insomnia, a prevalent mental disorder, is characterized by difficulties in initiating or maintaining sleep [8]. Those with insomnia may have difficulties falling or staying asleep or achieving good quality sleep. Sleep disturbance owing to chronic pain is characterized by prolonged sleep onset latency, poor maintenance of sleep, decreased total sleep time, decreased sleep efficiency, and overall poorer sleep quality. Additionally, patients with chronic pain frequently report sleep problems, and robust evidence supports the relationship between sleep disturbance and pain [6,9]. Notably, pain can act as a cause and consequence of sleep deficiency. Individuals with chronic pain, who also suffer from a severe level of sleep disturbance and depression, reported higher levels of pain-related impairment. However, even without severe depression, insomnia is associated with increased pain and distress. Insomnia symptoms are also correlated with more severe depression symptoms, including heightened suicidal tendencies. Furthermore, these symptoms predict poor depression treatment response in adults and adolescents [10].

The influence of pain on depression among patients with chronic pain can be adjusted by psychological status. Psychological inflexibility is the inability to fully focus on the present moment, to adapt to situations, and to change behavior to pursue more meaningful goals and values [11]. It refers to “the rigid dominance of psychological reactions over chosen values and contingencies in guiding actions.” [12] Psychological inflexibility is an important factor for mood swings and inefficient living in patients with chronic pain [13]. It manifests itself as short-term relief behaviors, such as physical inactivity and avoidance of activities that increase quality of life [14]. Over time, the patient’s avoidance of negative psychological events may induce an inflexible pattern of action [13].

Resilience, the ability to recover from adversity and adapt to stress, involves personality traits, social relationships, and contextual factors [15]. It includes perceiving stress as an opportunity for growth, adaptability, humor, and acceptance of limitations, while requiring patience and tolerance of emotional discomfort. Higher resilience reduces susceptibility to depression, even in chronic stress or trauma, due to psychological, emotional, behavioral, and social protective factors. Resilience is dynamic, influenced by internal and external factors, and has a reciprocal relationship with depression: enhanced resilience mitigates depressive symptoms, while depression can diminish resilience [16-18]. Existing research suggests that individuals who are psychologically resilient may be optimistic, see everything as a learning experience, focus on their strengths and qualities, use constructive criticism, establish close relationships with others, master social skills, and they are emotionally aware [19,20]. Patients with higher resilience recover from the negative effects of pain faster by effectively sustaining positive functioning and realizing personal growth despite the presence of pain [21]. Resilient individuals typically use active coping as a method of controlling their own pain and functioning, despite pain [21,22].

Examining these connections sheds light on how psychological inflexibility serves as a common mechanism, intensifying pain-related distress, depressive symptoms, and insomnia through maladaptive coping strategies. However, there is seldom a study which explores the associations among patients with chronic pain. This study aimed to explore the association of pain severity with insomnia, depression, and psychological status, such as psychological inflexibility or resilience, among patients with chronic pain. In addition, we examined whether psychological inflexibility, insomnia, or resilience may mediate the relationship between pain and depression. We posited that 1) the severity of pain is positively associated with depression, 2) insomnia is positively correlated with depression, 3) psychological inflexibility is positively correlated with depression, 4) resilience is negatively correlated with depression, 5) insomnia mediates the relationship between pain and depression, 6) psychological inflexibility may mediate the relationship between pain and depression, and 7) resilience may mediate the relationship between pain and depression among patients with chronic pain.

METHODS

Participants and procedures

We conducted an online survey among patients who visited the Pain Clinic in Asan Medical Center from August 14 to November 20, 2023, to assess their chronic pain that lasted for over 3 months [23]. Patients voluntarily participated in the survey through an enrollment poster advertised in the clinic. Information on participants’ age, sex, marital status, past psychiatric history, and current insomnia symptoms was collected. Additionally, they were asked about the cause and periods of pain experienced. The study protocol was approved by the Institutional Review Board (IRB) of the Asan Medical Center (2023-0753). Consent from patients was obtained by asking them to agree to participate. The requirement to obtain written informed consent was waived by the IRB because data was collected through an online survey.

Measures

Patient Health Questionnaire-9

The Patient Health Questionnaire-9 (PHQ-9) is a rating scale designed to assess depression severity [24]. It comprises 9 items and a 4-point Likert scale rating depression severity ranging from 0 (not at all) to 3 (nearly every day). The total score ranged from 0 to 27, and the higher the total score, the more severe the degree of depression. The Korean version of the PHQ-9 was used, and Cronbach’s alpha for this sample was 0.913.

Insomnia Severity Index

The Insomnia Severity Index (ISI) is a rating scale designed to assess the severity of insomnia [25]. It contains 7 items that rate insomnia severity on a 5-point Likert scale (0 to 4). The total score ranged from 0 to 28, and the higher the total score, the more severe the degree of insomnia. A validated Korean version of the ISI was used [26], and Cronbach’s alpha was 0.921.

Acceptance and Action Questionnaire-II

The Acceptance and Action Questionnaire-II (AAQ-II) is a rating scale of the revised version of the AAQ designed to assess psychological inflexibility [12]. It contains 10 items that rate psychological inflexibility on a 7-point Likert scale ranging from 1 (never true) to 7 (always true). Among the 10 items, items 1, 6, and 10 are scored reversely. The higher the total score, the higher the level of experiential avoidance or psychological inflexibility. We used the Korean version of the AAQ-II [27], and Cronbach’s alpha was 0.901.

Brief Resilience Scale

The Brief Resilience Scale (BRS) is a rating scale designed to assess the level of resilience [28]. It comprises 6 items that rate resilience on a 5-point Likert scale ranging from 1 to 5. Opposite scoring of two groups of items (items 1, 3, and 5 vs. items 2, 4, and 6) must be done. The total score ranged from 6 to 30, and the higher the total score, the higher the level of resilience. A validated Korean version was used [29], and Cronbach’s alpha was 0.927.

Statistical analysis

We described numeric variables as means and standard deviations. The significance level was defined as two tailed, p<0.05. We explored the influence of pain severity on depressive symptoms and the medicating effects of psychological factors. First, we performed a correlation analysis of pain severity and rating scales using Pearson’s correlation coefficients. Second, we performed linear regression analysis using enter methods to explore variables that predicted depressive symptoms. Third, we performed mediation analysis to examine whether pain severity directly influenced depression and whether psychological factors mediated the relationship using the bootstrap method with 2,000 resamples. Statistical analysis was performed using SPSS version 21.0, AMOS version 27 (IBM Corp., Inc., Armonk, NY, USA), and JASP version 0.14.1.0 (JASP Team, Amsterdam, Netherlands).

RESULTS

Table 1 serves as a comprehensive snapshot of the diverse demographic characteristics and clinical profiles of chronic pain. The study population exhibited a balanced gender distribution. The mean age of participants (44.9 years) indicates a diverse age range. The substantial standard deviation (12.8) shows variability in participants’ ages. The long duration of pain (mean: 50.4 months) underscores the chronic nature of the conditions under investigation. Patients’ marital statuses varied. Additionally, many patients had a psychiatric history. The International Classification of Diseases 11th Revision (ICD-11) classification provides a detailed breakdown of the types of chronic pain, with different severities of pain.

In Pearson’s correlation analysis, the PHQ-9 score was significantly correlated with the ISI (r=0.66, p<0.01), AAQ-II (r=0.71, p<0.01), BRS (r=-0.68, p<0.01), and pain severity (r=0.50, p<0.01) (Table 2). Pain severity was significantly correlated with the ISI (r=0.51, p<0.01), AAQ-II (r=0.38, p<0.01), and BRS (r=-0.34, p<0.01).

Linear regression analysis using enter methods was conducted to explore the variables that predicted the severity of depression among patients with chronic pain. The analysis showed that the severity of depression was predicted by pain severity (β=0.18, p=0.018), ISI (β=0.22, p=0.010), AAQ-II (β=0.32, p<0.001), and BRS (β=-0.28, p=0.002) (Table 3).

Mediation analysis showed that pain severity directly influenced the severity of depression. This relationship was partially mediated by insomnia severity, psychological inflexibility, and resilience (Table 4 and Figure 1).

DISCUSSION

This study explored the intricate relationships between chronic pain, psychological factors, insomnia, and depression. The correlation analysis revealed significant associations between pain severity and various psychological variables, emphasizing the interplay between physical and mental health. Linear regression analysis further identified predictors of depression among patients with chronic pain, highlighting pain and insomnia severity, psychological inflexibility, and resilience. Mediation analysis showed the direct and mediating effects of pain severity on depression through insomnia, psychological inflexibility, and resilience.

We found that pain is associated with depression. Our results are consistent with those of previous studies examining this relationship. Clinical studies showed that chronic pain, as a stress state, often induces depression [30], and up to 85% of patients with chronic pain suffer from severe depression [31]. Another study showed that 60.8% of patients with chronic pain experienced severe depression. They also had a greater number of absences from work and a higher inability to work owing to their ill health [31]. Based on biological evidence, depression affects central and peripheral neural pathways. As with the central pathway, the descending serotonin and noradrenergic pathways originate from the same neurons [32,33].

Moreover, we found that chronic pain is associated with psychological inflexibility. A recent study found that higher psychological flexibility is associated with lower pain catastrophizing [34]. Chronic pain significantly restricts patients’ physical activity, affecting their ability to work, engage with their children, maintain healthy relationships with their spouses, and perform routine tasks [35]. All these factors may align with the six dimensions of psychological inflexibility mentioned in the Introduction. Furthermore, inflexibility is related to depression. Higher pain ratings among patients with depression are attributed to limited psychosocial functioning and insufficient coping strategies [36]. As a result of not being able to adjust to the environment, stress can increase, possibly contributing to the onset and persistence of mental illnesses, such as depression and anxiety [37,38]. This aligns with the idea that psychological flexibility promotes adaptive coping [39]. A cycle of pain causing, and resulting from, psychological inflexibility over time can be observed [14].

Our study also demonstrated chronic pain is associated with insomnia and depression. Many other studies yielded similar results, where a significant coexistence of chronic pain and insomnia or a cause-and-effect relationship was present [40]. Moreover, insomnia has been identified as a precursor to depression. Increasing epidemiological evidence highlights sleep deficits and disturbances as risk factors for mental well-being [41]. A meta-analysis of 34 prospective cohort studies showed that insomnia was significantly associated with an increased risk of depression [42]. Experimental studies, using induced multiple nocturnal awakenings protocols, demonstrated anhedonia, catastrophic thinking, and increased arousal. Biochemically, depression is associated with a functional decrease in serotonergic neurotransmission and specific alterations of sleep, such as insomnia [43]. However, further studies are necessary to enhance our understanding of these associations.

Results show that a lower level of resilience is associated with chronic pain and depression. The effects of chronic pain on patients’ daily lives affect resilience. Similarly, a prior study reported significantly lower levels of resilience in people living with human immunodeficiency virus (HIV) and chronic pain, compared to people living with HIV without chronic pain [44]. Additionally, lower levels of resilience are associated with higher levels of depression. A significant association between resilience, physical activity, and psychological distress was observed. In psychology, resilience mechanisms modify the relationship between pain and outcome by enhancing coping responses to pain [21]. Active coping refers to directed actions by an individual in pain to control their own pain and function despite experiencing pain [22]. Active coping is associated with lower levels of depression. Resilience mechanisms are considered moderators of these interrelationships involving pain and outcomes related to health and well-being [28]. Patients with chronic pain gain resilience through optimism, purpose in life, and pain acceptance [45]. Furthermore, higher levels of optimism are related to lower levels of pain intensity and depressive symptoms in people in the early and intermediate stages of rheumatoid arthritis [46]. Thus, lower resilience negatively affects all these benefits, ultimately leading to depression.

This study has some limitations. First, the sample size was relatively small (n=100) because including patients with chronic pain was difficult. It cannot represent the general population and may increase the likelihood of a type II error. Second, although causes for chronic pain were evenly allocated based on ICD-11 (Table 1), all varying causes were not covered. Further research must be conducted to explore the psychological factors for each cause of chronic pain, because pain mechanisms may vary depending on the cause. Third, the study sample was from one tertiary-level general hospital in South Korea; thus, the results cannot be generalized. Fourth, we cannot present the causal relationship in this study. We surveyed the associations between chronic pain and psychiatric symptoms in a cross-sectional research design, and it needs to be explored longitudinally to examine the causal relationship. Finally, numerous potential factors exist that may mediate the relationship between pain and depression, such as anxiety, fear, and physical symptoms, which were not addressed in this study. Further research is needed to explore the mediating effects of omitted factors.

In conclusion, this study showed relationships between chronic pain, psychological factors, insomnia, and depression. In addition, we found the direct impact of pain severity on depression, insomnia, psychological inflexibility, and resilience acting as mediators. These findings guide clinical practices and inspire future research to explore targeted interventions and integrated models for a more effective approach to chronic pain management.

Notes

Availability of Data and Material

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

Seockhoon Chung, a contributing editor of the Psychiatry Investigation, was not involved in the editorial evaluation or decision to publish this article. All remaining authors have declared no conflicts of interest.

Author Contributions

Conceptualization: Hussein Makhour, Seockhoon Chung. Data curation: Seockhoon Chung. Formal analysis: Hussein Makhour, Seockhoon Chung. Methodology: Hussein Makhour, Seockhoon Chung. Writing—original draft: Hussein Makhour, Seockhoon Chung. Writing—review & editing: Hussein Makhour, Seockhoon Chung.

Funding Statement

None

Acknowledgments

None

Figure 1.

Mediation model showing the pathway from the effect of pain severity (independent variables) on depression (outcome) through insomnia, psychological inflexibility, and resilience (mediator) among participants with chronic pain. ^**p<0.01.

Table 1.

Baseline demographic and clinical characteristics of the participants (N=100)

Variable	Value
Sex, male	33 (33.0)
Age (years)	44.9±12.8
Duration of pain (months)	50.4±66.9
Marital status (single)
Single	40 (40.0)
Married, without kids	1 (1.0)
Married, with kids	54 (54.0)
Divorced	5 (5.0)
Psychiatric history
Have you experienced or have you been treated for depression, anxiety, or insomnia? (Yes)	57 (57.0)
Currently, do you think that you have psychiatric distress? (Yes)	49 (49.0)
Do you suffer from insomnia now? (Yes)	76 (76.0)
Chronic pain (ICD-11)
Chronic primary pain	13 (13.0)
Chronic cancer-related pain	15 (15.0)
Chronic surgical or posttraumatic pain	16 (16.0)
Chronic secondary musculoskeletal pain	14 (14.0)
Chronic secondary visceral pain	4 (4.0)
Chronic neuropathic pain	17 (17.0)
Chronic secondary headache or orofacial pain	10 (10.0)
Unknown	11 (11.0)
Symptoms rating
Pain severity (Numeric Rating Scale)	5.3±2.6
PHQ-9	12.3±7.2
ISI	15.1±6.8
AAQ-II	31.9±9.9
BRS	17.1±5.8

Data are presented as mean±standard deviation or number (%).

ICD-11, International Classification of Diseases 11th Revision; PHQ-9, Patient Health Questionnaire-9; ISI, Insomnia Severity Index; AAQ-II, Acceptance and Action Questionnaire-II; BRS, Brief Resilience Scale

Table 2.

Correlation coefficients of each variable for participants with chronic pain

Variables	Age	PHQ-9	ISI	AAQ-II	BRS
PHQ-9	-0.08
ISI	-0.13	0.66^**
AAQ-II	-0.13	0.71^**	0.59^**
BRS	0.15	-0.68^**	-0.53^**	-0.70^**
Pain severity	-0.14	0.50^**	0.51^**	0.38^**	-0.34^**

^** p<0.01.

PHQ-9, Patient Health Questionnaire-9; ISI, Insomnia Severity Index; AAQ-II, Acceptance and Action Questionnaire-II; BRS, Brief Resilience Scale

Table 3.

Linear regression analysis to explore variables that predict depression of participants with chronic pain

Dependent variables	Included parameters	β	p-value	Adjusted R²	F/p-value
PHQ-9	Age	0.05	0.398	0.63
	Pain severity	0.18	0.018		F=33.80
	ISI	0.22	0.010		p<0.001
	AAQ-II	0.32	<0.001
	BRS	-0.28	0.002

PHQ-9, Patient Health Questionnaire-9; ISI, Insomnia Severity Index; AAQ-II, Acceptance and Action Questionnaire-II; BRS, Brief Resilience Scale

Table 4.

The results of direct, indirect, and total effects on mediation analysis

Direct effect	Standardized estimator	Z-value	p-value	95% CI
Effect
Pain severity → Depression	0.17	2.41	0.016	0.03 to 0.31
Indirect effect
Pain severity → Insomnia → Depression	0.11	2.44	0.015	0.02 to 0.20
Pain severity → Inflexibility → Depression	0.12	2.66	0.008	0.03 to 0.21
Pain severity → Resilience → Depression	0.10	2.38	0.017	0.02 to 0.17
Path coefficients
Pain severity → Insomnia	0.51	5.88	<0.001	0.34 to 0.68
Insomnia → Depression	0.22	2.68	0.007	0.06 to 0.38
Pain severity → Inflexibility	0.38	4.02	<0.001	0.19 to 0.56
Inflexibility → Depression	0.32	3.55	<0.001	0.14 to 0.50
Pain severity → Resilience	-0.34	-3.56	<0.001	-0.53 to -0.15
Resilience → Depression	-0.28	-3.21	0.001	-0.45 to -0.11
Total effect
Pain severity → Depression	0.50	5.69	<0.001	0.33 to 0.67

CI, confidence interval

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