Context Little is known about the prevalence and characteristics of chronic
pain among patients with different types of chemical dependency.
Objectives To estimate the prevalence and to examine the characteristics of chronic
severe pain in chemically dependent populations receiving methadone maintenance
or inpatient residential treatment.
Design, Setting, and Participants Representative samples of 390 patients from 2 methadone maintenance
treatment programs (MMTPs) and 531 patients from 13 short-term residential
substance abuse treatment (inpatient) programs, all in New York State, were
surveyed in late 2000 and early 2001.
Main Outcome Measure Prevalence of chronic severe pain, defined as pain that persisted for
more than 6 months and was of moderate to severe intensity or that significantly
interfered with daily activities.
Results Chronic severe pain was experienced by 37% of MMTP patients (95% confidence
interval [CI], 32%-41%) and 24% of inpatients (95% CI, 20%-28%; P = .03). Pain of any type or duration during the past week was reported
by 80% of MMTP patients and 78% of inpatients. Among those with chronic severe
pain, 65% of MMTP patients and 48% of inpatients reported high levels of pain-related
interference in physical and psychosocial functioning. Among MMTP patients,
correlates of chronic pain in a multivariate model were age (odds ratio [OR],
2.08; 95% CI, 1.17-3.70), chronic illness (OR, 1.88; 95% CI, 1.07-3.29), lifetime
psychiatric illness (OR, 1.77; 95% CI, 1.06-2.97), psychiatric distress (OR,
1.63; 95% CI, 1.22-2.18), and time in treatment (OR, 2.23; 95% CI, 1.06-4.68).
Among inpatients, the correlates of chronic pain were race (blacks vs whites:
OR, 0.52; 95% CI, 0.31-0.90; Hispanics vs whites: OR, 0.48; 95% CI, 0.24-0.95),
drug craving (OR, 2.78; 95% CI, 1.54-5.02), chronic illness (OR, 2.17; 95%
CI, 1.37-3.43), and psychiatric distress (OR, 1.36; 95% CI, 1.03-1.81). Among
those with chronic severe pain, inpatients were significantly more likely
than MMTP patients to have used illicit drugs, as well as alcohol, to treat
their pain complaint (51% vs 34%, P = .005) but were
less likely to have been prescribed pain medications (52% vs 67%, P = .01).
Conclusions Chronic severe pain is prevalent among patients in substance abuse treatment,
especially MMTP patients. Pain is associated with functional impairment and
correlates of pain vary with the population. Self-medication for pain with
psychoactive drugs appears especially problematic among substance users who
enroll in drug-free treatment programs. Substance abuse treatment programs
need to develop comprehensive and structured pain management programs.
Although the relationships between chronic pain disorders and the diverse
types of chemical dependency are certain to be complex and clinically relevant,1 there have been few studies that directly explore
these phenomena. Pain is likely to be highly prevalent in populations with
chemical dependency, and it is possible that unrelieved pain could encourage
a variety of adverse outcomes, such as illicit drug use, use of nonprescribed
pain medication, or the negative medical and psychosocial effects associated
with continued drug-seeking behavior.2 It is
also possible that a drug abuse history could encourage the clinical misattribution
of pain complaints to the addictive disorder and lead to poor quality of care.3-5 These potential outcomes
highlight the need for studies that assess the frequency, characteristics,
impact, and treatment of pain in chemically dependent patients.
The prevalence of chronic pain in individuals with chemical dependency
is likely to be at least as high as in the general population. A review of
15 population-based surveys of chronic pain reported prevalences that varied
from 2% to 40% and cautiously estimated population prevalence at 10%.6 An international survey of 25 916 patients in
primary care centers revealed an overall pain prevalence of 22% and a prevalence
in the United States of 17% (Seattle, Wash).7 This
prevalence suggests that more than 70 million US adults have chronic pain.
Limited epidemiological data suggest that pain may be even more prevalent
in chemically dependent populations, that the experience of pain may interact
with substance use disorders in complex ways, and that pain is poorly managed
in the clinical setting. A study of 248 patients receiving methadone recorded
a pain prevalence of 61.3% and observed that those with pain had more medical
and psychiatric problems, and used more prescribed and nonprescribed medications,
than those without pain.8 Studies of chemically
dependent patients with pain associated with serious medical illnesses found
that pain therapy is often provided in a manner contrary to published guidelines.9,10
Existing studies of pain in chemically dependent individuals were not
designed to distinguish the subpopulation of patients with chronic pain disorders
severe enough to be clinically relevant. To draw meaningful conclusions about
the complex relationships between pain and the behaviors associated with drug
abuse, information about pain severity and other characteristics must be considered.
Using an operational definition of chronic pain (defined as pain that persisted
for >6 months and was of moderate to severe intensity or that significantly
interfered with daily activities), we conducted a study to determine pain
prevalence in 2 distinct populations: patients receiving methadone maintenance
for opioid addiction and patients who had recently enrolled in a short-term
residential treatment program, primarily for treatment of alcohol or cocaine
Data were collected from patients receiving methadone who were being
treated at 1 of 3 clinics housed within the same building and operated by
a large methadone maintenance treatment program (MMTP) in Brooklyn, NY, and
patients in a hospital-based MMTP in Manhattan, NY. These programs followed
federal methadone treatment admission protocols that require an opioid-dependent
diagnosis and an addiction history of at least 1 year.11 Data
were also collected in 13 public short-term inpatient rehabilitation programs
operated throughout the state of New York. The mean length of stay in these
inpatient programs is 3½ weeks. Most patients are admitted because
of current alcohol or cocaine dependence or both, and all had a lifetime diagnosis
of alcohol abuse or dependence. The institutional review board of the National
Development and Research Institutes approved the research protocol and oral
informed consent was obtained from the study patients.
Sample size was not predetermined. As many cases as possible were recruited
within the study sites. A power analysis was performed by using the logistic
regression module of the PASS 2002 program (NCSS Statistical Software, Kaysville,
Utah). Results showed that, for a desired power of 80% and α = .05,
we could reliably detect odds ratios (ORs) for binary predictors between 1.89
and 2.34 for the MMTP sample and 1.73 and 2.07 for the inpatient sample. Detectable
ORs were smaller when there was less redundancy between one predictor and
other predictors and larger when there was more redundancy.
The Brooklyn MMTP patients were randomly recruited based on the weekly
urine collection schedule for all patients. Data collection was performed
during the first 2 weeks of March 2001 and continued until data had been obtained
from at least 30% of the MMTP population at that site. All patients at the
Manhattan MMTP were recruited because of the smaller number of patients at
that site. Data collection at the Manhattan site occurred between September
20 and October 30, 2000. Of the MMTP patients approached for the survey, 153
of 229 (67%) agreed to participate.
Inpatients were enrolled between October 11 and November 29, 2000. For
each inpatient program, data were collected on 1 or more (up to 4) consecutive
days. A total of 545 of 604 (90%) eligible patients completed the survey.
The protocol was designed to allow flexibility in the procedure for
questionnaire completion. Depending on the resources of the site or on respondent
preference, the questionnaire was either read by a study aide in a group setting,
self-administered in a group setting supervised by a study aide, administered
in a face-to-face interview, or self-administered.
The questionnaire included no identifying information and patients were
instructed not to indicate their names on the form. Specific items captured
demographic information and history related to substance abuse; substance
abuse treatment; pain severity, type, duration, and life interference; general
health; and the use of medications to treat pain. Most items required a yes
or no answer or a response on a numeric rating scale. In an effort to reduce
missing data, the questionnaire was brief (typically completed in <10 minutes).
Skip patterns were not used (ie, patients were instructed to answer all questions
whether or not they had pain). The questionnaire was pilot tested in an inpatient
program and in a focus group of needle exchange clients to improve its content
Pain severity was measured with a numeric scale (no pain = 0 to pain
as bad as you can imagine = 10) adapted from the Brief Pain Inventory (BPI).12 Patients were asked to indicate the severity of their
pain at its worst during the past week.
The extent to which pain interfered with various domains of functioning
was assessed using the pain interference BPI subscale. The 7-item subscale
measures pain interference in different domains, such as walking, sleep, and
social relationships, by using numeric scales (pain does not interfere = 0
to pain completely interferes = 10). This subscale has been extensively validated,
and a relationship between overall pain interference (mean scores of the 7
items) and worst pain severity has been empirically confirmed.13
Psychiatric distress was measured with a 6-item validated version of
the widely used Symptom Checklist-90 (SCL-90).14,15 None
of the 6 psychiatric distress items referred to somatic symptoms. Lifetime
psychiatric illness was determined by asking respondents if they had ever
been diagnosed with a mental health or psychiatric disorder.
A checklist was used to record drugs, including alcohol, that were used
during the patient's last week of active use. Drug craving was measured on
a numeric scale (no urge to use = 0 to uncontrollable urge to use = 10).
Checklists also were used to record chronic illnesses, use of pain medications,
and visits to physicians for a pain complaint. Three categories of pain medications
were assessed: medications prescribed by a physician, over-the-counter (OTC)
medications, and illicit "street" drugs used to treat pain. Use of street
drugs was defined as "Illegal drugs, alcohol, or medications that you got
on the street or from friends or family for the purpose of treating a physical
pain." Use of pain medications and physician visits were coded "yes" if the
event had occurred within the past 3 months. As a statistical control for
withdrawal pain, patients were asked to report how often they "felt pain due
to drug or alcohol withdrawal or drug/alcohol hunger." Responses could range
from 0 (not at all or less than 1 day) to 3 (5-7 days).
To operationally define a subpopulation of patients with chronic pain
that was relatively likely to be clinically significant, an index of "chronic
severe pain" was defined as a score of 5 or higher on the BPI item "worst
pain in the past week" or of 5 or higher on the BPI pain interference scale,
and pain duration for at least 6 months. Our operational definition was based
on a cross-national study that indicated that a pain intensity rating of 5
or greater on a 0- to 10-point scale was the pain score at which a significant
accumulation of functional deficits in multiple domains is reported.13
Most of the statistical procedures represent separate but parallel analyses
conducted for MMTP patients and inpatients. Using the operational definition
of chronic severe pain, we calculated pain prevalence and the prevalences
of covariates of interest for each of the 2 study samples. To present percentages
and more interpretable ORs, the withdrawal pain variable was recoded so that
the highest value represented 3 to 7 days and the rating scales that had more
than 4 data points (eg, the 11-point scales) were collapsed into a fewer number
of categories. Bivariate analysis (χ2 test) was used to examine
the relationships between respondent characteristics and chronic pain. This
method closely followed the strategy used by Galea et al.16 We
also used χ2 analysis to compare patients with and without
chronic severe pain for physician contact and use of pain medications. Rates
of pain medication use by MMTP patients and inpatients with chronic severe
pain also were compared. To identify characteristics uniquely associated with
chronic severe pain, variables correlated with pain (P<.10;
2-tailed) in the bivariate analyses were entered into a multivariate logistic
regression model; forced method of entry was used to retain all selected variables
in the model. Adequacy of the 2 models was determined with the Hosmer-Lemeshow
goodness-of-fit test17 and by examining the
estimated SEs of the parameters and the estimated coefficients.
Although missing data were uncommon for any specific variable (ranging
from 0%-10% of cases) and did not influence the bivariate analyses, exclusion
of patients with any missing data from the multivariate logistic regression
analysis would have substantially decreased the number of cases for analysis.
To avoid this problem, we used a hot-deck data imputation procedure that replaces
the missing data with a value from a similar completed case.18,19 The
imputation procedure was done using the software R20 and
other analyses were performed using SPSS Version 11.0 (SPSS Inc, Chicago,
Ill). Statistical significance for all outcomes was set at P<.05.
Patients were excluded from the analysis if missing data precluded the
designation of chronic severe pain. Eight of the 153 patients recruited from
the Manhattan MMTP, 18 of the 263 patients from the Brooklyn MMTP, and 14
of the 545 inpatients were excluded for this reason.
The mean (SD) age of the MMTP patients (n = 390) was 43 (9.4) years;
38% were women, 25% were white, 36% were black, and 33% were Hispanic. The
3 most frequently reported primary or secondary problem substances used were
heroin (88%), alcohol (77%), and cocaine (34%). The mean (SD) methadone dose
was 78.2 (45.0) mg/d. More than half (58.5%) had been enrolled in methadone
treatment for more than 2 years.
Among inpatients (n = 531), the mean (SD) age was 36 (9.1) years; 20%
were women, 44% were white, 31% were black, and 16% were Hispanic. The 3 most
frequently reported primary or secondary problem substances used were alcohol
(74%), cocaine (54%), and heroin (15%). Approximately two thirds (66.5%) had
been enrolled in their inpatient program for fewer than 2 weeks.
Pain Prevalence, Characteristics, and Impact
The prevalence of chronic severe pain among MMTP patients was 37% (95%
confidence interval [CI], 32%-41%). There was no difference in pain prevalence
between the Brooklyn and the Manhattan programs (38% vs 35%, respectively, P = .64). The prevalence of chronic pain among those in
the inpatient program was 24% (95% CI, 20%-28%). The difference between the
groups was significant (P = .03).
Most of the patients in each of the study samples reported some type
of pain during the past week (MMTP, 80%; inpatients, 78%). Sixty-one percent
of these MMTP patients had pain for more than 6 months, 48% had pain for 1
year or longer, and 30% had pain for more than 5 years. Among the inpatients,
48% had pain for more than 6 months, 42% had pain for 1 year or longer, and
24% had pain for more than 5 years.
Among those with pain of any type, pain severity varied. The "worst
pain" scale from the BPI was divided into categories that meaningfully depict
mild, moderate, and severe pain on the basis of pain interference with function13: mild pain, 1-4; moderate pain, 5-6; and severe pain,
7-10. Among MMTP patients with any pain for any duration, the percentage with
moderate to severe pain was 60% (188/313); severe pain was reported by 38%
(119/313). Among inpatients with any pain for any duration, the percentage
with moderate to severe pain was 47% (193/412) and the percentage with severe
pain was 27% (110/412).
Although pain severity was a criterion for categorizing the groups with
clinically significant chronic severe pain (37% of the MMTP patients and 24%
of the inpatients), severity also varied among these patients. Severe pain
was reported by 66% (94/143) of these MMTP patients and 57% (73/128) of these
inpatients. All of these chronic pain patients had pain for at least 6 months.
Among patients with any pain (80% MMTP; 78% inpatients), pain severity
and pain duration were correlated (r = 0.36, P<.001 for MMTP patients and r =
0.28, P<.001 for inpatients) (Figure 1). This association between pain duration and severity was
particularly strong among MMTP patients, especially when the lowest and highest
pain duration categories were compared. For MMTP patients with less than 1
month of pain (n = 75), the percentages with mild, moderate, and severe pain
severity were 64%, 19%, and 17%, respectively. Among MMTP patients reporting
more than 5 years of pain (n = 94), pain severity was reported as mild (20%),
moderate (21%), and severe (59%).
The degree to which pain interfered with various domains of functioning
was evaluated with the BPI pain interference scale. The mean of the scores
on the 7 items in this scale provides an overall measure of interference.
Among those with any pain for any duration, a mean score of 5 or higher was
reported by 125 of 313 (40%) MMTP patients and 95 of 412 (23%) inpatients.
Among those with chronic severe pain, 93 of 143 (65%) MMTP patients and 61
of 128 (48%) inpatients had a mean score of 5 or higher. Pain-related interference
with sleep was the greatest problem (eg, 73% for MMTP patients with chronic
pain), followed by interference in affect (mood, enjoyment), physical activity
(walking, general activity), and social relationships (Figure 2). Pain-related interference with work must be interpreted
cautiously because most patients were not employed at the time of the survey.
Correlates of Chronic Severe Pain
In bivariate analyses, the variables that were associated (P<.10) with chronic severe pain in the MMTP sample were withdrawal
pain, age, chronic illness, psychiatric diagnosis, psychiatric distress, pain
as a reason for first using drugs, drug craving, and time in treatment (Table 1). There was no significant difference
in mean (SD) methadone dose between MMTP patients with and without chronic
pain (82.0 [45.2] mg/d vs 76.0 [44.9] mg/d, respectively; t359 = 1.21, P = .23).
The variables associated with chronic severe pain in the inpatient sample
were similar, but not identical, to those associated with pain in the MMTP
sample. There were significant correlations between chronic severe pain and
withdrawal pain, sex, race, chronic illness, psychiatric diagnosis, psychiatric
distress, pain as a reason for first using drugs, multiple drug use, and drug
Among MMTP patients, the relationship between chronic severe pain and
having any chronic illness was similar whether or not arthritis was included
as an illness criterion (r = 0.22, r = 0.24; both P<.001). Among inpatients,
however, the correlation between chronic severe pain and chronic illness changed
from r = 0.20 (P<.001)
when arthritis was included as an illness criterion to r = 0.09 (P = .08) when arthritis was removed.
That is, arthritis contributed to the correlation between chronic pain and
chronic illness to a greater extent among the patients admitted for residential
treatment than for the MMTP patients. For both the MMTP and inpatient samples,
the correlation between arthritis and chronic pain was significant (both r = 0.30, P<.001).
Multivariate Analysis: Predictors of Chronic Severe Pain
The variables that were associated (P<.10)
with pain in the bivariate analysis were entered into the multiple regression
model (Table 2). In the MMTP sample,
the significant (P<.05) predictors of chronic
pain were age, presence of chronic illness, psychiatric diagnosis, psychiatric
distress, and time in treatment. The significant predictors of chronic pain
in the inpatient sample were race, presence of chronic illness, drug craving,
and psychiatric distress (Table 2).
The adequacy of the 2 multivariate models was supported with nonsignificant
results from the Hosmer-Lemeshow goodness-of-fit test (P = .24 for MMTP sample; P = .87 for inpatient
sample) and the absence of problems related to collinearity or overfitting.
Among MMTP patients, those with chronic severe pain were significantly
more likely than those without pain to have visited a physician during the
prior 3 months for any reason (75% vs 55%, P<.001)
or specifically for a pain complaint (60% vs 36%, P<.001).
Among the inpatients, however, the proportion that visited physicians during
the prior 3 months did not vary with pain. Seventy-three percent of the inpatients
with chronic severe pain and 73% of those without pain visited a physician
for any reason, whereas 52% with pain and 45% without pain visited a physician
for a specific pain complaint (P = .13).
In the MMTP sample, patients with chronic severe pain were significantly
more likely to have been prescribed analgesic drugs than those without chronic
severe pain and to have taken OTC medications for pain (Figure 3). There was no difference between those with and without
chronic severe pain in the use of illicit drugs to treat a pain complaint.
In contrast, inpatients with chronic severe pain were significantly more likely
than those without chronic severe pain to have used illicit drugs to self-medicate.
Although inpatients with chronic severe pain also were more likely to use
OTC medications than those without it, there was no difference between those
with or without chronic severe pain in the proportion prescribed an analgesic.
Among those with chronic severe pain, MMTP patients were significantly
more likely than inpatients to have been prescribed pain medications by a
physician during the past 3 months (67% vs 52%, P =
.01). Among MMTP patients with chronic severe pain, the most frequently prescribed
analgesics were opioids (47%), most often codeine, methadone, oxycodone, and
hydrocodone (Table 3). The most
frequently prescribed drugs for inpatients with chronic severe pain were nonsteroidal
anti-inflammatory drugs (22%). Only 17% of the inpatients had been prescribed
opioids for pain. Codeine (with and without acetaminophen), hydrocodone, and
oxycodone were the most frequently prescribed opioids (Table 3).
Use of OTC drugs by those with chronic severe pain did not vary between
the groups (75% MMTP vs 72% inpatient, P = .49).
Among both samples, ibuprofen was the most frequent, acetaminophen the second
most frequent, and aspirin the least frequent OTC drug used in the past 3
As noted, among those with chronic severe pain, the use of an illicit
drug to treat pain during the prior 3 months was significantly more likely
to be reported by inpatients than by MMTP patients (51% vs 34%, P = .005). The illicit drugs most frequently used to treat pain by
inpatients with chronic severe pain were alcohol (35%), cocaine (29%), opioids
(26%), and marijuana (26%). Among MMTP patients with chronic severe pain,
the most frequently used illicit drugs were opioids (30%).
Pain was very prevalent in representative samples of 2 distinct populations
with chemical dependency, and chronic severe pain was experienced by a substantial
minority of both groups. Methadone patients differed from patients recently
admitted to a residential treatment center in numerous ways and had a significantly
higher prevalence of chronic pain (37% vs 24%). Although comparisons with
other studies of pain epidemiology are difficult to make because of methodological
differences, the prevalence of chronic pain in these samples is in the upper
range reported in surveys of the general population.6,7 The
prevalence of chronic pain in these chemically dependent patients also compares
with that in surveys of cancer patients undergoing active therapy, approximately
a third of whom have pain severe enough to warrant opioid therapy.21,22
There is great variability in the experience of pain. Although some
patients expressed relatively little impairment in function or life enjoyment
as a result of their pain, others appeared to be significantly compromised.
Relatively high scores on the various items of the BPI pain interference scale
were reported by 55% to 73% of MMTP patients and 44% to 62% of inpatients
with severe chronic pain, respectively. Data of this type may be helpful in
clarifying unmet needs and the changes that would be necessary in the health
care system to address these needs.
Consistent with findings from surveys of the general population7 and a prior survey of MMTP patients,8 chronic
pain was associated with both physical and psychiatric illness. Among inpatients,
however, psychiatric illness was not a predictor of chronic pain in the multivariate
analysis, suggesting that the association between psychiatric illness and
chronic pain among inpatients could be explained by other correlates of chronic
pain, such as chronic illness, drug craving, and psychiatric distress.
Many chronic illnesses are painful and an association between physical
illness and pain was expected. The differences between patient samples, however,
illustrate the complexity of these medical factors. Among the inpatients,
the association between illness and pain was largely explained by arthritis.
In contrast, the exclusion of arthritis as a criterion for chronic illness
did not attenuate the association between chronic illness and chronic pain
among MMTP patients. It is possible that this finding is explained by a higher
prevalence of HIV/AIDS among MMTP patients, which may be associated with painful
chronic illness of more diverse types.23 Additional
studies are needed to clarify the important disease-related factors that may
lead to chronic pain in populations with chemical dependency.
Given the large variation in populations with chemical dependency, the
relationships between pain and substance abuse also are likely to be highly
complex. In our study, there was greater evidence for an association between
substance use and chronic pain among inpatients than among MMTP patients.
Among inpatients, there were significant bivariate relationships between chronic
pain and pain as a reason for first using drugs, multiple drug use, and drug
craving. In the multivariate analysis, only drug craving remained significantly
associated with chronic pain. Not surprisingly, inpatients with pain were
significantly more likely than those without pain to attribute the use of
alcohol and other illicit drugs, such as cocaine and marijuana, to a need
for pain control. These results suggest that chronic pain contributes to illicit
drug use behavior among persons who were recently using alcohol and/or cocaine.
Inpatients with chronic pain visited physicians and received legitimate pain
medications no more frequently than those without pain, raising the possibility
that undertreatment or inability to access appropriate medical care may be
a factor in the decision to use illicit drugs for pain.
Although MMTP patients were significantly more likely than inpatients
to report chronic pain, and almost a quarter reported that pain was one of
the reasons for first using drugs, there was relatively little evidence that
pain was associated with current levels of substance abuse. In the multivariate
analysis, the associations between chronic pain and the substance abuse behaviors
observed in the bivariate analysis (pain as a reason for first using drugs
and drug craving) were not sustained. Moreover, the bivariate associations
that were found in the inpatient group between chronic pain and multiple drug
use, and between pain and the use of illicit drugs to treat pain complaints,
were not identified among MMTP patients.
The reasons that abuse behaviors were associated with pain in the inpatients
but not the MMTP patients are unknown. Studies are needed to evaluate more
fully the range of potential variables that may mediate this relationship.
The association between race and chronic pain among inpatients was unexpected
given the variable findings of prior pain studies. For example, a study that
compared black vs white women with rheumatoid arthritis found no difference
in pain severity between the 2 groups,24 whereas
a postoperative pain study observed that patients of European descent reported
significantly less severe pain than blacks or Hispanics.25 The
absence of an association between chronic pain and race among the MMTP sample
suggests that other factors may have accounted for the significant association
between these 2 variables in the inpatient sample. Inpatients were more diverse
in their drug use patterns (eg, alcohol, cocaine, or both), had recently enrolled
in substance abuse treatment, and were recruited across a broader geographical
area. Methadone patients had been admitted to treatment because of a single
drug use disorder (opioid dependence), were recruited in an urban setting,
and were likely to have been in treatment for an extended period.
The undertreatment of pain is a significant concern in populations with
chemical dependency. In painful disorders for which there is a broad consensus
about the role of opioid therapy, specifically cancer and AIDS-related pain,
studies have documented that this treatment commonly diverges from accepted
is far more challenging to assess when a broad consensus concerning optimal
treatment approaches does not exist. It would be difficult, therefore, to
determine the extent to which the pain and functional impairments experienced
by patients in this study relate to inadequate pain management. However, given
the number of barriers identified as potential reasons for inadequate pain
management, it is appropriate to raise concerns about undertreatment and to
investigate it further.5,8,26,27 The
barriers are complex and may involve institutional practices, inadequate training
and skills of clinicians, lack of access to health care, reluctance of physicians
to prescribe opioids to individuals with a history of chemical dependency
(especially opioid addiction), and reluctance on the part of the chemically
dependent person to seek medical care because of stigma or fear of relapse.
Although the association between time in methadone treatment and chronic
severe pain in our multivariate model is unexplained, it underscores the chronicity
of pain complaints among MMTP patients and the necessity of long-term management
of pain in an important segment of this population. In laboratory studies
using experimentally induced pain, MMTP patients have been shown to have lower
pain thresholds compared with matched controls (persons with no history of
substance abuse or dependence), cocaine abusers, and former heroin users not
receiving opioid agonist therapy.28,29 The
findings of lower pain threshold and higher chronic pain prevalence emphasize
the need for competent pain assessment and management in this population.29
Our study had several important limitations. Given the lack of instruments
that have been validated, that are brief and multidimensional, and that have
proven utility in populations with chemical dependency, our questionnaire
had only face, content, and factorial validity. Factor analysis performed
with the BPI pain severity and interference items yielded the 2 expected factors
(data are available from the author). The development of validated questions
in this area would be useful research. At minimum, our results require replication
in future work. This study did not include a standardized measure of withdrawal
pain. However, participants in our focus group reported that they were able
to distinguish withdrawal pain from other types of pain. Chronic pain is typically
localized and persists, although with varying degrees of severity, for long
periods of time.30 Withdrawal pain is short-lived,
not localized, and, in the case of opioid withdrawal, is reported as causing
flu-like symptoms.31,32 Inclusion
of withdrawal pain as a covariate in the multivariate analysis also helped
to distinguish withdrawal pain from chronic pain.
The brevity of the questionnaire, which was needed to encourage a good
response, precluded collection of much important information. Additional studies
need to clarify pain syndromes, provide additional data about pain characteristics,
evaluate the impact of pain on physical and psychosocial functioning, and
explore the relationship between pain and drug abuse, including first use
and relapse. Studies also are needed to evaluate pain treatment in chemically
dependent populations and determine the extent to which access to care and
other factors implicate undertreatment as a cause of unrelieved pain.
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