Chronic pain (CP) is defined as pain that persists beyond the normal tissue healing period, typically lasting approximately 3 months. It is a major health concern affecting approximately 30% of people worldwide [1]. CP is more prevalent and burdensome among populations experiencing vulnerability, including women, older adults, children, individuals from racial or ethnic minority groups, and those from lower socioeconomic backgrounds [2,3]. In Europe, the economic burden of CP could reach up to €300 billion annually (US $343 billion) [4].

There is broad consensus that understanding and treating CP requires a biopsychosocial approach. Beyond biological and physiological factors, psychological, social, and life experiences play a crucial role in the development, exacerbation, and persistence of pain [5-7]. Notably, CP is a well-documented consequence of another public health problem, intimate partner violence (IPV) against women, as demonstrated by controlled studies in both population-based and clinical samples [8-11].

IPV against women is a gender-based issue [12-14] that encompasses physical, psychological, or sexual violence perpetrated by some men against their female partners [15]. Today, IPV against women remains a widespread epidemic, affecting at least 30% of women worldwide [16]. It has severe health and social consequences [17] and imposes an economic cost of €174 billion (US $199 billion) per year on the European Union [18].

Compared to women who have not experienced violence, those exposed to IPV against women report a higher prevalence of fibromyalgia, abdominal pain, genitourinary tract pain, pelvic and genital pain, headaches (including migraines), and back and neck pain [19-22]. A study conducted with 108 male and female patients with CP attending a rehabilitation center found that 56% had a current or past history of IPV, with more than 80% being women. Nearly 30% had experienced IPV within the previous year [23].

Other studies have shown that those who have experienced IPV and are living with sickle cell disease are 5 times more likely to report CP than those who have never experienced IPV [24]. In addition, they are nearly twice as likely to develop fibromyalgia and chronic fatigue syndrome [25]. A recent systematic review and meta-analysis found strong and consistent associations between women who have experienced violence—whether by a partner or others—and CP conditions [26]. Furthermore, IPV against women is often linked to disabling pain [8,23,27]. Survivors with disabilities are more likely to report generalized CP than those with other disabling health conditions [28], and more than one-third continue to experience a high level of pain-related disability long after ending the abusive relationship [29].

Women who have experienced IPV also frequently use medication to alleviate pain [30]; for example, individuals with sickle cell disease who have experienced interpersonal violence are more than 6 times as likely to use opiate-based medications daily compared to those without a history of violence exposure [24].

Given the increased likelihood of those with exposure to IPV against women developing disabling CP and experiencing worse health outcomes [23,24,28,30]—even after leaving a violent relationship [29]—it is possible that experiencing (or having experienced) IPV against women influences the risk and protective factors involved in the development and maintenance of disabling CP differently. While previous studies have examined factors that predict or contribute to CP in those with exposure to violence [31,32], to our knowledge, no comparative studies have explored whether the underlying factors of CP differ based on a history of interpersonal violence.

Gathering this information is crucial for early detection and tailored treatment strategies for CP management in women who have experienced IPV as well as those who have not. Some researchers suggest that women with CP who are experiencing IPV may require more holistic care and support [26]. In addition, there is a need to better understand the daily experience of women living with CP while currently experiencing IPV compared to that of women who experience CP without a history of experiencing violence. However, no studies on this topic were found in the reviewed literature. In fact, the intersection of CP and IPV against women as interrelated phenomena has received little research attention [23].

This research project has 2 general objectives and 6 specific aims.

First, we seek to understand the meaning and implications of living with CP for women experiencing IPV compared to those with CP alone. From this point forward, the term “women with CP alone” will refer to women who have never experienced any form of psychological, physical, or sexual violence at any stage of their lives, whether perpetrated by an intimate partner or another known or unknown individual. We include other forms of violence beyond IPV against women because they may also influence CP management and health outcomes [31].

More specifically, by comparing women with CP and exposure to IPV to women with CP alone, we aim to (1) examine how CP affects their daily lives, (2) identify the impact that CP may have on their intimate relationship and vice versa, (3) understand how they self-manage CP, and (4) describe their experiences with health systems.

Second, we aim to determine whether women with CP alone, women with CP who are currently experiencing IPV, and women with CP who have a past history of IPV present distinct profiles based on risk and protective factors for disabling CP and health outcomes. If differences exist, we will also (5) identify the factors that best explain these profiles and (6) detect more specific subprofiles within each group.

Ultimately, the findings will be used to develop assessment and intervention guidelines for health and social service professionals.

Approval has been obtained from the ethics committee of Miguel Hernández University (DCC.ANR.240227) and the Public Health Ethics Committee for Research of the Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (CEI-SP 20240531/05/P).

Ethical requirements will be consistent across both studies. All participants will receive a letter with a description of the study and of the individual interview content and questionnaires that they will have to fill in depending on the study in which they participate. There will not be any incentive for participation.

For the qualitative phase (phase 1), participants will sign an informed consent form, which clearly states that participation is voluntary and that they can withdraw at any time. Before the interviews, they will have to complete a web-based questionnaire to check whether they meet the inclusion criteria. Participants will submit their informed consent to a designated professional at the relevant health center, unit, or association, who will assign a code to each participant and will also be responsible for ensuring the correct completion of the web-based questionnaires with the corresponding code. Participants who do not meet the inclusion criteria will have their questionnaires deleted, and the informed consent forms for nonparticipants will be discarded by the professionals. Participants who meet the inclusion criteria will be interviewed. Interviews will be audio recorded for analysis purposes and erased afterward. The informed consent forms will be securely handed over by the professionals to the principal investigator in a sealed envelope. The professionals will also schedule the interview date and communicate the participant’s code number to the research team, ensuring that the interview and questionnaire data match. The research team will not have access to any personal identifying information, such as names.

For the quantitative phase (phase 2), participants will fill in anonymous web-based questionnaires, as outlined in the informed consent form. For security reasons, participants must complete the questionnaire at the center they attend. Allowing them to complete it at home could put them at risk because their aggressors could see their responses. Participants will submit their informed consent to a designated professional at the relevant health center, unit, or association. This professional will have a list of codes. They will have to assign one to each participant (unknown to them) and will have to enter it so that each participant can start or pick up the questionnaire where they left off the last time. The professional will collect all informed consent forms and submit them to the principal investigator in a sealed envelope. Throughout the study, the research team will not have access to any personal identifying information.

In both studies, the web-based closed questionnaires will be designed using LimeSurvey, a private platform that meets security standards and data protection regulations. The responses will be stored in a database under the supervision of one of the collaborating universities. Before commencing the studies, the questionnaires will be piloted with a sample of 10 women to address any issues related to content, usability, or technical functionality of the web-based platform.

To distinguish participants with acute pain from those with CP, they will first be asked how long they have been experiencing pain. Participants will also select the type of CP they experience, such as fibromyalgia, from a provided list.

Participants will have to indicate their age, sex at birth, gender identification, racial and ethnic identity, sexual orientation, and relationship status (whether currently in a relationship and for how long).

Participants will complete an inventory [127] consisting of 32 items that assess various forms of violence exerted by a partner: 11 items on physical violence, 4 on sexual violence, and 17 on emotional and psychological violence. Participants will respond with the frequency of each type of violence (0=never, 1=once, and 2=more than once) and specify whether the violence was inflicted by a past or current partner, including the duration of the violent relationship. A woman will be classified as experiencing current IPV or having experienced past IPV if she reports experiencing any item more than once from the same partner.

The original version of this checklist [128] contains 17 items referring to different stressful events. Participants will have to mark whether they have experienced, witnessed, or learned about each event; whether it was part of their job; or whether it does not apply to them. The adapted version will rephrase the items on physical and sexual assault (items 6 to 9) into a single item: exposure to “psychological, physical, and/or sexual violence or abuse at any stage of your life by a known or unknown person other than an intimate partner.”

The purpose of using this instrument is helping to control for any external traumatic events (eg, natural disasters) that may influence pain experiences different from experiencing IPV.

These variables are described in detail in the phase 1 CP and Type and Sociodemographic Characteristics subsections.

Participants will have to indicate how they accessed the study (associations and support centers for IPV against women, CP associations, CP units, or primary health care centers).

Age, belonging to a minority group (yes or no), years of education, annual household and personal incomes (categorized as €0 to €19,000; €20,000 to €40,000; and >€40,000; 1€=US $1.14), relationship status (single, partnered, or married), relationship duration (years), relationship satisfaction (10-point scale), CP diagnosis (yes or no), and time since CP diagnosis (years).

Gender norms and identity will be measured using the Conformity to Feminine Norms Inventory-45 [135,136]. The Spanish-adapted version of the inventory [137] consists of 23 items rated on a 4-point response scale ranging from 0=strongly disagree to 3=strongly agree. The inventory includes 7 subscales: care for children, invest in appearance, domestic, romantic relationship, nice in relationships, thinness, and modesty. It is designed to assess the degree to which women conform to traditional femininity norms as reflected in their behaviors, feelings, and thoughts. Higher scores on this inventory indicate a greater adherence to these traditional femininity norms. The Conformity to Feminine Norms Inventory- has demonstrated good psychometric properties, making it a reliable measure for evaluating conformity to feminine norms.

These scales have been described in study 1. With regard to the IPV against women questionnaire, participants will have to indicate whether they are currently experiencing such situations or have experienced them in the past and for how long. In addition, those women who have experienced IPV in the past will be asked how long they have lived free from violence.

The 3 activity patterns—pacing, avoidance, and persistence—can serve different goals and have varying impacts on health outcomes. To measure these patterns, we will use the Activity Patterns Scale [138]. This scale consists of 8 subscales, each with 3 items, for a total of 24 items. The subscales include pain avoidance, activity avoidance, task-contingent persistence, excessive persistence, pain-contingent persistence, pacing to increase activity levels, pacing to conserve energy for valued activities, and pacing to reduce pain. Participants will rate how well each statement applies to them on a 5-point scale ranging from 0=not at all to 4=always. Higher scores in a subscale indicate a stronger tendency to display the corresponding activity pattern. The instrument demonstrates adequate reliability as well as structural, convergent, and criteria validity. It has been specifically developed for use with the Spanish population [138].

Although some studies advocate the use of objective measures of physical activity and physical exercise [139], the International Physical Activity Questionnaire (IPAQ) [140] allows the collection of detailed information on physical activity performance comparable to that collected with objective measures such as pedometers [141]. The short, self-administered version of the IPAQ focuses on the past 7 days and consists of 7 items that estimate the time spent on moderate to vigorous physical activity, such as walking, bicycling, or heavy lifting, in at least 10-minute bouts over the week. This version provides a continuous score reflecting the minutes of physical activity performed, with higher scores indicating greater physical activity. The IPAQ presents good psychometric properties and is available in Spanish [140].

This scale [142] contains 13 items that are rated on a 5-point scale ranging from 0=not at all to 4=all the time. It assesses the 3 components of catastrophizing: rumination, magnification, and helplessness. The total score ranges from 0 to 52 points. Higher scores reflect higher levels of catastrophic thoughts. The Spanish version [143] presents strong psychometric properties.

This specific scale [144] for patients with CP helps measure perceived self-efficacy and capability to manage pain consequences. It is composed of 22 items structured across 3 factors: self-efficacy to control pain, self-efficacy for physical functioning, and self-efficacy for symptom control. It is a well-known instrument that has been validated with the Spanish population with good psychometric properties [145]. In the Spanish version items are rated from 0=I think I am totally incapable to 10=I think I am totally capable, with a higher score suggesting higher self-efficacy in a specific factor or in the overall measure of self-efficacy.

This instrument [146] consists of 11 items designed to measure both emotional and instrumental social support in relation to promoting functional autonomy or addressing functional dependence. Participants are asked to rate how frequently their family members have provided support when they were in pain. In our case we specifically ask on the support they receive from their intimate partners. Only women currently in a relationship will be required to complete this section. Responses are provided on a Likert scale ranging from 1=not at all frequent to 5=extremely frequent. Higher scores indicate that participants perceive more frequent support for functional autonomy or dependence. This instrument has demonstrated validity and reliability in its original form and has been validated with the Spanish population [146].

This tool [147] consists of 12 items that measure both positive and negative health states across 8 health concepts (physical functioning, role limitations because of physical health problems, bodily pain, general health, vitality, social functioning, role limitations because of emotional problems, and mental health). It offers 2 physical and mental health summary measures. The responses are based on Likert scales ranging from 3 to 5 points. This questionnaire has been validated for use with the Spanish population [148].

The Brief Pain Inventory–Short Form [149] assesses pain severity and pain interference. The latter includes 7 items that assess pain’s impact on various areas of life (general activity, mood, ability to walk, work, social relationships, sleep, and the ability to enjoy activities), which participants rate on a 10-point scale (maximum score=70). For the purpose of evaluating physical functioning, items related to general activity, ability to walk, and ability to work will be selected, with a maximum score of 30. This instrument has been validated for use with the Spanish population [150].

This scale [151] includes 2 subscales, one for anxiety and one for depression, each with 7 items and a 4-point response scale ranging from 0=no presence or minimum presence to 3=maximum presence. The scale assesses emotional distress in patients with chronic conditions, focusing on the cognitive and behavioral symptoms of anxiety and depression. The recommended cutoff scores for possible cases are 8 for both subscales, with scores of >10 indicating probable cases. This scale has been widely validated across multiple countries, including Spain, and demonstrates strong psychometric properties [152].

Participants will be asked whether they have ever considered committing suicide (yes or no); how frequently they have had such thoughts (never, rarely, sometimes, often, or always); and the number of suicide attempts, if any.

Participants will be asked to indicate the types of analgesics prescribed for their CP condition and their adherence to the prescribed medication regimen. They will be asked if they are taking the medication as prescribed, not taking it at all, or taking it in lesser or greater amounts. The questionnaire will also inquire about the use of nonprescribed medications and the consumption of other legal (eg, alcohol) and illegal drugs (eg, marijuana) for pain management. In addition, participants will be asked about other prescribed medications they may be taking and the purposes for which these medications are used.

Participants will be asked about the frequency of visits to their general practitioner. Specifically, they will be asked how many times per month they visit their general practitioner, with the following response options: none, only when needing medication prescriptions or check-ups, at least once a month, or ≥2 times per month.

This project has 2 main aims. The first is to acquire knowledge on the meaning and implications of living with CP for women experiencing IPV compared to those with CP alone. In this regard, we hypothesize that (1) women who experience any form of IPV (psychological, physical, or sexual) will report a greater daily impact of CP on their functionality than those with CP alone; (2) compared to the latter, the former will report a stronger bidirectional relationship between CP and intimate relationship dynamics as well as worse health outcomes (ie, episodes of violence will increase CP symptomatology and vice versa), with such a negative cycle being more prevalent; and (3) CP management and experiences with the health system will be better among women with CP alone. Hypotheses 1 and 3 are based on the fact that some authors have highlighted that the impact of IPV against women on the health of those affected adds to CP [31]. This could impair their ability to self-manage CP, leading to increased medication use and more frequent visits to health centers [165]. We believe that this result will be independent of the type of violence experienced because studies have shown that psychological violence alone can negatively impact CP severity and disability [166,167].

Regarding our second hypothesis, we expect that aggressors will present more hostility and criticism toward their partners’ health conditions as a way to undermine them, increase dependence, and control them, considering violence as an instrumental component [165]. We also expect that periods of violence will be linked to an increase in CP symptomatology. However, in women with CP alone, their partners will likely promote autonomy by encouraging and reinforcing healthy behaviors or promote dependence by maintaining disabling pain behaviors through solicitousness. In this group of women, even if hostile responses can also be present sometimes, their impact on CP will be less significant because they need to take place in a context of low marital satisfaction [95,96], and we assume that levels of marital satisfaction will be higher among women with CP alone. In addition, we expect that periods with an increase in CP symptomology will be more related to external stressors than to the relationship itself.

Second, we aim to identify whether women with CP alone, those with CP and currently experiencing IPV, and those with CP and a past history of IPV present different profiles based on risk and protective factors for (disabling) CP and health outcomes. We hypothesize that women with CP and current or past experiences of IPV will show higher levels of disabling pain, more excessive persistence or avoidance activity patterns, lower levels of exercise, worse pain-related self-efficacy, greater pain worrying, informal social support that fosters dependence, lower levels of physical functioning, greater anxiety and depression, poorer medication management, increased illegal drug use, more suicidal thoughts and attempts, and a higher frequency of health system use. This hypothesis is based on previous findings indicating higher levels of disabling pain in women experiencing IPV compared to those with CP alone, as well as higher levels of suicidal thoughts, addiction issues, and greater use of health services compared to the general female population [23,165]. These characteristics will likely worsen in the presence of PTSD [82]. In addition, because pain-related self-efficacy and pain worrying have been linked to CP [65-69,78], we expect these factors to most effectively account for the profiles of women with a current or past history of IPV, along with informal social support, for the aforementioned reasons.

Moreover, because AI techniques go beyond traditional inferential statistics, it can identify patterns and relationships between variables that might remain undetected by the human eye. AI may uncover specific profiles within different groups of women, revealing how factors such as educational background, traditional feminine roles, ethnicity, and the duration of violence intersect with CP-related variables; for example, it could be that the pattern of excessive persistence is more common in women who are in the initial stages of the relationship and that they may seek to conform to traditional gender roles in an effort to meet their aggressors’ expectations. AI’s ability to process large datasets could lead to new insights and advances in understanding pain, its management, and its relationship with other concurrent psychosocial factors.

This study is not without limitations. One of the main challenges is the high number of participants required for the quantitative study. To mitigate this issue, we will contact primary health care centers, associations and support centers for IPV against women, CP associations, and CP units across the province of Alicante. A second limitation is the use of nonprobability sampling, which may introduce bias. However, this research aims to provide a preliminary understanding of the co-occurrence of these 2 significant health issues; to the best of our knowledge, it will be the first to do so with a large sample using AI. A third limitation concerns the number of questionnaires that need to be completed in the second study. To address this, participants’ responses will be saved, and they will be given ample time to complete all questionnaires. In addition, the order of presentation will be randomized to reduce the likelihood that the same questionnaires are consistently left unanswered. We hope this will result in a similar number of responses across all questionnaires. To further encourage questionnaire completion, we will ask the center directors and professionals to remind participants about the importance of answering all questions.

A fourth limitation is the focus on only individual and relational factors. While community and societal factors also influence CP and its disabling effects [168], the primary aim of this study is to enhance the detection and treatment of CP in health care settings by personalizing care. Therefore, the focus is placed on individual and relational factors. Finally, not all scales have been validated with Spanish samples. Validating several scales has high costs and is time consuming, but we will conduct translation and back-translation procedures and test the instruments directly with the population. Moreover, the study will only be conducted in the province of Alicante. However, if profiles are identified, we plan to extend the second study to other Spanish regions as well as other countries while controlling for other macrovariables (eg, free access to the health system) to analyze the commonalities and differences in the profiles. If minimal or no differences are found, the profiles could be largely explained by the experience of IPV against women, and recommendations could be generalized to similar countries.

In 2023, the European Pain Federation identified 7 key areas of focus in pain research [169], two of which are central to our study: (1) understanding and addressing comorbidities that complicate management and recovery; and (2) personalizing pain management because current treatments remain uniform, regardless of factors such as gender, age, lifestyle, or overall health. Our research directly addresses both areas. First, we tackle 2 closely related yet under-studied health issues: CP and IPV against women. As Craner et al [23] have noted, most research on traumatic events and CP has concentrated on childhood trauma and posttraumatic stress symptoms, with limited attention given to IPV against women. Second, our study aims to identify profiles based on risk factors and health outcomes, which could enhance detection and help design more personalized treatments.

In addition, our study could indirectly have a positive impact on costs and contribute to achieving the United Nations’ Sustainable Development Goals. Both CP and IPV against women have significant consequences for individuals and societies, with economic costs of at least €300 billion and €172 billion, respectively (US $343 billion and US $197 billion) [4,18]. These high costs primarily stem from frequent primary health care consultations, diagnostic procedures, medication, therapies (eg, psychology, occupational therapy, infiltrations, or surgery), hospitalizations, and loss of work productivity. As a result, both health issues severely affect productivity and the health care system [121,170], threatening human capital and hindering progress toward the United Nations’ Sustainable Development Goals. We believe that by improving the detection of IPV against women associated with CP and tailoring treatments to the identified risk factors and health outcomes, our study can help reduce costs and advance progress toward achieving the United Nations’ Sustainable Development Goals. Effective self-management could alleviate the burden that CP places on the health care system and reduce its economic costs [171,172].