Alcohol and Opioid Use in Chronic Pain: A Cross-Sectional Examination of Differences in Functioning Based on Misuse Status

Abstract

Opioid misuse is regularly associated with disrupted functioning in those with chronic pain. Less work has examined whether alcohol misuse may also interfere with functioning. This study examined frequency of opioid and alcohol misuse in 131 individuals (61.1% female) prescribed opioids for the treatment of chronic pain. Participants completed an anonymous survey online, consisting of measures of pain, functioning, and opioid and alcohol misuse. Cut scores were used to categorize individuals according to substance misuse status. Individuals were categorized as follows: 35.9% (n = 47) were not misusing either opioids or alcohol, 22.9% (n = 30) were misusing both opioids and alcohol, 38.2% (n = 50) were misusing opioids alone, and only 3.0% (n = 4) were misusing alcohol alone. A multivariate analysis of variance was performed to examine differences in pain and functioning between groups (after excluding individuals in the alcohol misuse group due to the small sample size). Group comparisons indicated that individuals who were not misusing either substance were less disabled and distressed in comparison to those who were misusing opioids alone or both opioids and alcohol. No differences were indicated between the latter 2 groups. Overall, the observed frequency of opioid misuse was somewhat higher in comparison to previous work (approximately 1 out of every 3 participants), and misuse of both alcohol and opioids was common (approximately 1 out of every 5 participants). While these data are preliminary, they do suggest that issues of substance misuse in those with chronic pain extends beyond opioids alone.

Perspective:

Opioid and alcohol misuse was examined in 131 individuals prescribed opioids for chronic pain. In total, 35.9% were not misusing either, 22.9% were misusing both, 38.2% were misusing opioids, and 3.1% were misusing alcohol. Individuals not misusing either were generally less disabled and distressed compared to those misusing opioids or both.

Opioids are commonly prescribed for the treatment of chronic pain. Rates of opioid prescribing for pain vary across settings and locations, with estimates of approximately 20% in a nationally representative survey in 2010¹³ to 58% in a community-based health care system in 2012.⁵³ Although opioids have evidence for pain reduction, they also increase risk of morbidity and mortality.^{10,11,16,36,47} Several observational surveys have indicated that rates of opioid-related problems have increased in a manner that parallels the increases in opioid prescription rates over the past few decades.^9,60 These risks are significantly increased when opioids are mis-used.^37,59,73 A number of studies suggest that opioid misuse in those with chronic pain is associated with greater levels of distress and disability, increased risk of overdose, greater healthcare costs, and decreased probability of success from rehabilitative treatments.^{21,42,44,63,67}

These adverse impacts are unsurprising in many ways, given that misuse of illicit and licit substances often imparts significant risks for individuals and society. Alcohol misuse is perhaps the most well-researched example. Alcohol use disorder (AUD) is one of the most common psychiatric diagnoses, with 29% of individuals in the United States meeting lifetime criteria²⁴ and with rates of excessive alcohol use, such as binge drinking, exceeding 30% in some countries.⁷² AUD is associated with disruptions across a host of body systems, and both AUD and alcohol misuse are associated with significant morbidity and mortality.^{5,35,49,55,57,61,62}

Several studies have examined opioid misuse impact in chronic pain, but less work has examined issues of alcohol misuse alone or in combination with opioid misuse. This area would seem important, given that alcohol co-use is relatively common in those who use prescribed opioids, ranging from 12% to 36% across published work.^20,34,48,56 Furthermore, alcohol and opioid co-use substantially increases risk of overdose.^17,20,25,68 To our knowledge, only a single study has examined frequency and impact of alcohol misuse in a sample of individuals on long-term opioid therapy.³⁴ This study found that “risky drinkers,” defined as those who had consumed 5 or more drinks on at least 1 single occasion within the past year, reported higher levels of pain interference in comparison to “nonrisky” drinkers.

Given the frequency and risks associated with co-use, there is a need to examine broader impacts of problematic, high-risk drinking in those who are using prescribed opioids for the treatment of chronic pain. The purpose of this study was twofold. First, we screened for opioid and alcohol misuse in a sample of individuals who had been prescribed opioids for chronic pain. These results were used to classify individuals into 1 of 4 misuse groups: 1) no opioid or alcohol misuse, 2) both opioid and alcohol misuse, 3) only opioid misuse, and 4) only alcohol misuse. Next, differences in pain-related physical and psychosocial functioning across these groups were examined to determine if misuse of either or both substances was associated with differential disruptions in functioning. We included both measures of negative functioning (ie, distress, depression, disability) and positive functioning (ie, pain acceptance, success in valued activity, adaptive pain behavior) to allow for a broad analysis of participant information across both maladaptive and adaptive impacts of pain. It was hypothesized that individuals with evidence of misuse of both substances would have the greatest levels of disruption, followed by individuals misusing only 1 of the substances. Individuals with no evidence of substance misuse were expected to have the lowest levels of disrupted functioning.

Methods

Participants

Participants were recruited using an on-line data collection system, the Amazon Mechanical Turk. This system allows researchers to collect secure and confidential data, as researchers only have access to a “worker ID” that is not linked to any protected health information. Participants were compensated $3.00 for completing the survey. This study was approved by the University of New Mexico’s Human Subjects Institutional Review Board.

Prior to completing the survey, all potential participants completed an unpaid screening survey, which was used to evaluate study inclusion criteria. To be eligible, participants had to report that they experienced pain: 1) on most days of the week (ie, 4 or more days per week), 2) at an average weekly intensity of 3 or greater on an 11-point numerical rating scale (NRS), 3) for a duration of at least 3 months, and 4) not restricted to headache pain alone. In total, 420 individuals met these initial inclusion criteria and began the survey. Seventeen individuals (4.4%) provided data that was not useable; of these individuals, responses were either missing entirely (n = 10) or included demographic information only (n = 7). These individuals were excluded from further analyses.

For the present analyses, data from 131 individuals who provided data and who reported taking prescribed opioids for the treatment of chronic pain were used (32.5% of the total recruited sample). Most of these individuals were female (61.1%), of white, non-Hispanic ethnicity (80.0%; Asian: 7.7%, Hispanic: 6.2%, black: 5.4%, other: 0.8%), and married or cohabitating (55.8%; single: 33.3%, divorced: 9.3%, widowed 1.6%). The average age was 36.6 years (standard deviation [SD] = 11.8). The mean years of education was 15.5 (SD = 2.3), which corresponded to the greatest proportion of individuals reporting that they had completed “some college” as their highest level of education (38.2%; bachelor’s degree: 33.6%, postgraduate degree: 13.7%, technical/trade school degree: 8.4%, high school degree: 6.1%).

As noted, all participants reported the presence of chronic pain. The most frequently reported pain location was low back (53.2%; neck: 12.9%, full body: 10.5%, lower extremity: 9.7%, upper extremity: 8.1%, hips/pelvis: 4.0%, mid-back: 1.6%). Secondary pain sites were reported by 23.0% of individuals. Pain duration averaged 6.7 years (SD = 6.1). Just over half of the participants were employed (33.6% full time and 23.6% part time), and 34.4% were unemployed. An additional 6.1% reported working as a homemaker and 2.3% were retired.

Measures

Participants completed a battery of questionnaires, which included an assessment of demographic variables (including gender, age, years of education, and employment status) and pain-related details (including pain duration and location). Usual pain intensity and pain-related distress over the past week were assessed with a NRS (0 [no pain] to 10 [maximum possible pain]). Participants also completed a battery of self-report measures of psychosocial and physical functioning, which included measures of depression, physical and psychosocial disability, pain acceptance, and adaptive pain responding.

Depression was evaluated using the British Columbia Major Depression Inventory BCMDI, [²⁹] a 16-item measure based on the diagnostic criteria for major depressive disorder from the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders.¹ Possible scores for the British Columbia Major Depression Inventory range from 0 to 80. Previous work has supported the psychometric properties of the measure.²⁹ In the present sample, internal consistency was acceptable (Cronbach α = .90).

Physical and psychosocial disability was assessed using the chronic pain-specific version of the Sickness Impact Profile (SIP-CP).⁴¹ The physical disability domain score of the SIP-CP includes items that evaluate functioning across body care, movement, mobility, and ambulation. The psychosocial disability domain score includes 26 items evaluating functioning across communication, alertness, emotional functioning, and social interaction. Both physical and psychosocial disability scores range from 0 to 1, with higher scores indicating greater disability. The SIP-CP development study used an item response theory approach to identify items of the longer SIP⁴ that were specifically appropriate for use in a chronic pain sample.⁴¹ This same development study provided evidence for the convergent validity of the SIP-CP’s 2 domain scores, as there were reliable correlations with relevant measures of chronic pain-related functioning. In the present sample, the Kuder-Richardson coefficient (for dichotomous items) was used to evaluate internal consistency of the SIP-CP, which was acceptable for both the physical and psychosocial disability subscales (.70 and .85, respectively).

Pain acceptance was evaluated using the Chronic Pain Acceptance Questionnaire (CPAQ).³⁹ The CPAQ has 20 items that evaluate engagement in important activities even with the continued experience of pain and the degree to which respondents are willing to experience pain in the service of activity. The CPAQ has been widely used in chronic pain settings and typically is viewed as a measure of adaptive responding to chronic pain, in that higher scores are negatively correlated with distress and disability and positively correlated with measures of healthy functioning.^18,38,52,66 Possible scores range from 0 to 120. The CPAQ’s factor structure has been supported.^54,64,70 Internal consistency in the present sample was acceptable (Cronbach α = .90).

Adaptive pain behavior was evaluated using scores from 2 measures: the values success subscale of the Valued Living Scale (VLS)³⁰ and the total score of the Brief Pain Response Inventory (BPRI).⁴⁰ The VLS evaluates success in valued domains across 8 areas: health, emotional well-being, friendships, productivity, community, caregiving/parenting, spirituality, and marital/romantic partnerships. Possible scores range from 0 to 80, with higher scores indicating more success in these valued domains. The BPRI includes 15 items that evaluate aspects of healthy responding to chronic pain. For example, items evaluate frequency of nonavoidant pain responding and the frequency with which activity is moderated to allow for consistent pursuit of meaningful activity. The possible total score ranges from 0 to 105, with higher scores indicating greater frequency of healthy responding. As is the case with CPAQ scores, greater scores for both the VLS and BPRI are generally negatively correlated with measures of distress and disability and positively correlated with measures of adaptive functioning.^30,40 The internal consistency scores for the VLS and BPRI were acceptable in the present sample (Cronbach α = .81 and .88, respectively).

Opioid misuse was assessed using the Current Opioid Misuse Measure (COMM).⁸ The COMM consists of 17 items, which assess patterns and frequency of opioid use, cognitive difficulties, suicidal ideation, and anger/irritability. Scores on the COMM range from 0 to 68. Both the original evaluation study and subsequent work have indicated that a cut score of 9 or above, out of a possible range of 0 to 68, has reasonable sensitivity and specificity^7,8 for opioid misuse. Internal consistency in the present sample was acceptable (Cronbach α = .86).

Alcohol misuse was assessed using the 10-item Alcohol Use Disorders Identification Test (AUDIT).⁶ The AUDIT is a well-established screening measure of problematic drinking and has strong evidence of validity and reliability across a variety of clinical and nonclinical samples.^50,51 Scores can range from 0 to 40, with higher scores indicating greater probability of risky alcohol use. The recommended cut score for risk of alcohol misuse is 7 for women and 8 for men. Internal consistency in the present sample was acceptable (Cronbach α =.90).

Analytic Approach

Initially, scores on both the COMM and the AUDIT for each individual were interpreted relative to recommended cut scores. As mentioned above, participants were then placed into 1 of 4 groups based on misuse status: 1) no opioid or alcohol misuse, 2) both opioid and alcohol misuse, 3) only opioid misuse, and 4) only alcohol misuse.

Following categorization according to substance misuse status, a multivariate analysis of variance (MANOVA) was performed to investigate differences on measures of functioning across the 4 groups. Dependent measures included usual pain intensity, weekly pain-related distress, depression, physical disability, psychosocial disability, pain acceptance, success in valued activities, frequency of healthy pain responding, and scores on the opioid and alcohol misuse measures. It was planned that a significant overall omnibus test would be followed by a test of between-subject effects for each dependent measure, which if significant, would then be followed by pairwise comparisons using a Bonferroni-corrected alpha to control for the probability of type 1 error. Estimates of effect size for between group differences, partial eta², were calculated. Partial eta² measures the proportion of the total variance in dependent measures accounted for by between-group differences. A maximum likelihood procedure was used to make use of all available data.

Results

The proportion of individuals in each risk category was as follows: 35.9% (n = 47) were not misusing either opioids or alcohol, 22.9% (n = 30) were misusing both opioids and alcohol, 38.2% (n = 50) were misusing opioids alone, and only 3.1% (n = 4) were misusing alcohol alone. Because of the small number of individuals in the alcohol misuse-only category, this group was eliminated from further analyses. Descriptive statistics for each of the measures used to create the categories are provided in the Table. Overall, the means of the measures in this sample all fall within 1 SD of published normative data.^{6,8,30,40,41,66}

Table.

Means (SDs) for Study Measures

Dependent Measure	Risk Group Classification				Full Sample (n = 131)
	No Misuse Risk (n = 47)	Opioid and Alcohol misuse risk (n = 30)	Opioid Misuse Risk (n = 50)	Alcohol Misuse Risk (n = 4)
Usual pain intensity (past wk)	4.7 (1.4) a	4.6 (1.6) a	5.4 (1.4) a	4.0 (0.8)	4.9 (1.5)
Pain-related distress (past wk)	3.9 (2.4) a	5.8 (2.1) b	5.6 (2.5) b	3.8 (2.6)	4.9 (2.5)
Depression	14.2 (10.5) a	32.1 (12.6) b	31.5 (13.4) b	21.5 (1.7)	25.1 (14.6)
Physical disability	.10 (.11) a	.11 (.13) a	.15 (.13) a	.19 (.17)	.12 (.12)
Psychosocial disability	.11 (.09) a	.26 (.21) b	.29 (.18) b	.33 (.12)	.22 (.18)
Pain acceptance	69.0 (13.2) a	58.2 (16.0) b	53.0 (17.6) b	67.8 (14.3)	60.1 (17.1)
Values success	41.7 (13.8) a	30.4 (12.5) b	28.0 (12.5) b	26.8 (7.2)	33.4 (14.2)
Adaptive pain behavior	74.7 (17.3) a	54.3 (16.7) b	56.5 (20.7) b	78.5 (17.9)	63.2 (20.7)
Opioid misuse risk	5.0 (2.0) a	19.7 (9.1) b	16.9 (7.0) b	6.3 (1.7)	12.9 (8.9)
Alcohol misuse risk	2.5 (2.4) a	15.2 (7.0) b	2.4 (2.1) a	14.0 (8.5)	5.7 (6.9)

NOTE. The risk of alcohol misuse group was not included in MANOVA comparisons due to its small sample size.

Different superscripts indicate significantly different pairwise comparisons at the between-group level using a Bonferroni-controlled alpha.

Opioid misuse risk was measured using the COMM, alcohol misuse risk was measured using the Alcohol Use Disorders Screening Test, usual pain intensity and pain-related distress were measured using a 0 (no pain) to 10 (maximum pain) NRS, depression was measured using the BCMDI, physical and psychosocial disability were measured using the SIP-CP, pain acceptance was measured using the CPAQ, values success was measured using the VLS, and adaptive pain behavior was measured using the BPRI.

As mentioned above, differences among these groups across measures of pain-related functioning were then evaluated using a MANOVA. The omnibus test was significant (Wilks’s lambda = .13, P < .001, partial eta² = .65). Follow-up ANOVAs were significant for all measures of functioning (all F [2, 126] > 8.0, all P < .001, range partial eta² = .13 - .70) with only 2 exceptions, which were for pain intensity and physical disability (F [2, 126] < 1.8, P > .17, partial eta² = .03 in each case).

The results of the pairwise comparisons are displayed in the Table. The pattern of group differences across 8 of 9 analyses were identical such that individuals who were not misusing either substance were functioning better than either of the other 2 groups. Specifically, the group with no misuse reported lower levels of pain-related distress, depression, physical and psychosocial disability, and opioid or alcohol misuse. This group also reported greater pain acceptance, success in valued areas, and frequency of adaptive pain behavior. No between-group differences were indicated between the group misusing both alcohol and opioids and the group misusing opioids alone. The sole exception to this finding was for alcohol misuse, for which individuals who were misusing both substances had higher AUDIT scores then either of the other 2 groups (ie, no misuse, opioid misuse alone). These latter 2 groups did not differ on AUDIT scores.

Discussion

The current study examined frequency of opioid and alcohol misuse in adults with chronic pain who were prescribed opioids for pain treatment and the association between alcohol and opioid misuse and functioning. Overall, results indicated that misuse of both opioids and alcohol or misuse of opioids alone were frequent and reliably associated with more pain-related distress, depression, and psychosocial disability and less acceptance, engagement in valued activity, and adaptive pain behavior, in comparison to no misuse of either substance. Misuse of alcohol alone was rare in this sample, suggesting that alcohol and opioid misuse are more likely to co-occur than for alcohol misuse to occur in the absence of opioid misuse.

The overall proportion of alcohol misuse among individuals also misusing opioids in this sample of opioid-prescribed individuals with chronic pain is noteworthy. As previously cited, there is only 1 other study, to our knowledge, that has specifically examined risky alcohol use in individuals who are taking opioids for the treatment of chronic pain. This study, by Larance et al,³⁴ found that 24% of an Australian sample engaged in risky drinking, defined as the consumption of more than 4 standard drinks on at least 1 occasion in the past 12 months. The overall proportion of individuals misusing alcohol from our sample was similar, as 26% of individuals were identified as risky drinkers overall, with the majority also identified as risky opioid users as well. If it is indeed accurate that approximately 1 in 4 individuals prescribed opioids for the treatment of chronic pain are drinking in a problematic manner, then there is a clear need to address alcohol use in pain treatment settings. Areas for focused effort include improved assessment of alcohol consumption, additional investigation into the potential adverse consequences associated with risky alcohol consumption in this population, and the development of appropriate interventions to decrease risky use and minimize the likelihood of adverse events. Concomitant use of opioids and alcohol significantly increases risk of overdose, as both are central nervous system depressants.^17,25 Recent toxicology reports of opioid-related overdose deaths have indicated that alcohol and other sedatives are regularly present in the blood of the decedents.^{9,22,23,25,31,32} In combination, these issues would seem to suggest important areas for future clinical and research work among opioid-prescribed patients with chronic pain.

With regard to treatment options within the addictions field, there is reasonably good evidence regarding the efficacy of brief interventions in reducing alcohol consumption.^33,69 For example, the “SBIRT” framework (Screening, Brief Intervention, and Referral to Treatment) is an approach to decrease risk for development of a substance use disorder and identify patients in need of substance abuse treatment.² Adaptation of SBIRT for patients with chronic pain is one potential clinical option to better assess and address the needs of these patients. Increased patient education regarding the complex interactions and risks associated with co-occurring opioid and alcohol use is recommended for patients receiving opioids for chronic pain management, perhaps alongside opioid agonist treatment for those meeting criteria for an opioid use disorder,⁴⁶ both preventatively and upon identification of opioid misuse, alcohol misuse, or both. Further, formal examination into patients’ perceived reasons for substance use (eg, pain reduction, coping, relaxation, to alleviate emotional distress) could provide meaningful guidance regarding needed treatment targets in this population and components missing in traditional approaches to pain treatment. Substance use may also be a potentially salient variable missing in current measures of chronic pain risk stratification (see Hill et al²⁶); substance misuse was associated with poorer functioning across multiple domains in the present data.

It was hypothesized that misuse of both alcohol and opioids would represent a significantly greater risk to functioning in comparison to opioid misuse alone, but this hypothesis was not supported. No significant differences in functioning were indicated between these 2 misuse groups. This finding is surprising given the fact that polysubstance use disorder is generally more disruptive and difficult to treat then a single substance use disorder.^12,15 It is possible that the independent effects of chronic pain and opioid misuse on physical and emotional functioning are significantly large enough to render any additional difficulties caused by alcohol misuse nonsignificant. Some of the raw differences observed between misuse groups could, however, be meaningful, and it may be that these differences would be significant in a larger sample. For example, opioid misuse and alcohol misuse is higher in the combined group in comparison to the single substance groups (d = .34 for opioid misuse and d = .15 for alcohol misuse). Thus these results are likely best considered preliminary and are in need of further examination in larger samples, including those specifically presenting to treatment clinics.

Relatedly, it has been argued that a robust predictor of eventual opioid-related morbidity or mortality is a history of a substance use disorder.^28,43,44 From these data, it is unclear how many individuals in the current sample had such a history or had a current substance use disorder (versus subclinical levels of risky use behavior). It is also unclear in the current data if patients were using substances other than alcohol or opioids. Future studies should assess for history of a substance use disorder along with current levels of substance use, including substances beyond alcohol and opioids.

The use of self-report measures of pain symptoms and opioid prescription is a limitation; however, the number of individuals with self-reported chronic pain who received opioid prescriptions in the current sample (32.5%) is consistent within the wide range indicated by other studies that report rates of opioid prescribing for chronic pain (ie, 20% – 58%).^13,45,53 Similarly, the use of self-report screening measures to identify those at risk of opioid or alcohol misuse is an additional limitation of the present work; however, the confidential nature of the data collection and strong psychometric properties of the 2 measures used offer some counterbalance to this issue and may have aided in more accurate reporting. If we assume that the overall reporting of risk status is accurate, there are a few points that warrant further discussion.

First, the overall frequency of opioid misuse (61.1%, the sum of both the opioids-only risk group and the opioids and alcohol risk group) was higher than what has typically been reported in previous work.^19,27,36,65 Although it is not possible to precisely identify the reasons that frequency was so high in this sample, this finding does suggest that continued attention to issues of substance misuse in this population is important, particularly given the association between misuse and poorer functioning.

Second, care must be taken when interpreting the results from screening measures, as the positive predictive value of screening measures for opioid use disorders is complicated by the variance in (generally low) base rates for this condition in patients with chronic pain.^3,58 When screening for conditions with low base rates such as this one, screeners are typically most accurate for ruling out or predicting those who will not misuse opioids. Thus findings in the current study indicating risk for opioid and alcohol misuse must be interpreted with caution. Given the cross-sectional nature of this study, it is impossible to know how many cases are false positives for substance misuse. Ideally, for those flagging up as at risk for misuse, additional data would be collected to corroborate the screener data (eg, clinical interview or urine drug screen).

Finally, the problems related to the significant increases in opioid prescription rates in many countries have been well-documented and there is a significant amount of current academic, governmental, and media attention on this issue.¹⁴ Opioids are certainly a problem, but it is important to also consider problems in alcohol use as well. Both are legally obtainable and potentially easy to use in a risky manner. The available evidence suggests their potential for negative impact is enhanced when they are co-used in those with chronic pain (see Witkiewitz and Vowles⁷¹ for a review). Furthermore, while current guidelines for individuals providing treatment to patients on long-term opioid therapy for chronic pain emphasize the importance of frequent screening for risky opioid use, there is much less attention given to the need to screen for alcohol misuse.

In closing, results from this study demonstrate the need for increased research and clinical investigation into assessing and treating opioid and alcohol misuse behaviors in patients with chronic pain. Evidence in the current study indicate that patients at risk for misusing opioids and alcohol are functioning at lower levels and experiencing lower quality of life, compared to those not misusing substances. Chronic pain is a complex condition that can have a multifaceted impact on functioning without the presence of substance misuse. When it is accompanied by the latter, it is assumed that this complexity is increased significantly. At present, there are few treatment options available that combine appropriate chronic pain and substance misuse interventions. Data such as those presented here suggest that there is a significant need for the development of such options, both in relation to opioid misuse, but crucially also for alcohol misuse and alcohol and opioid co-use.