Abstract
Objectives:
Stimulant use is a growing problem, but little is known about service utilization among patients with stimulant use disorder (StUD). In the context of the overdose crisis, much research has focused on patients with opioid use disorder (OUD). It is unclear how the characteristics, treatment receipt and hospitalization of patients with StUD differ from patients with OUD.
Methods:
Electronic health record data were extracted for national Veterans Health Administration (VHA) patients with a visit 3/1/2020–2/28/2021 with StUD and/or OUD (N=132,273). We compared patients with StUD without OUD to those with 1) co-occurring StUD+OUD and 2) OUD without StUD. Patient characteristics, substance use disorder treatment and hospitalizations in the year following patients’ first study period visit were descriptively compared. Treatment and hospitalization were also compared in adjusted regression models.
Results:
Compared to patients with OUD+StUD, those with StUD without OUD were less likely to receive outpatient (adjusted odds ratio [aOR] 0.49, 95% confidence interval [CI] 0.47–0.50) or any treatment (aOR 0.47, 95% CI 0.46–0.49). Compared to patients with OUD without StUD, those with StUD without OUD were less likely to receive outpatient (aOR 0.51, 95% CI 0.49–0.52) or any treatment (aOR 0.56, 95% CI 0.54–0.58) and more likely to receive residential treatment (aOR 2.18, 95% 2.05–2.30) and to be hospitalized (aOR 1.62, 95% 1.56–1.69).
Conclusions:
Patients with StUD may be less likely to receive treatment and more likely to be hospitalized than patients with OUD. Efforts focused on mitigating hospitalization and increasing treatment receipt for patients with StUD are needed.
Keywords: stimulant use disorder, opioid use disorder, treatment, hospitalization, veterans
INTRODUCTION
Over 4.5 million United States residents had stimulant use disorder (StUD) in 2022,1 and stimulant-involved overdoses—both with and without the involvement of opioids—have increased substantially. From 2013 to 2019, the stimulant-involved overdose death rate increased by 317%.2 Among Veterans Health Administration (VHA) patients, stimulant-involved overdose deaths were over 3 times as high in 2018 compared to 2012.3 Prior research suggests that stimulant use increases risk of hospitalization,4,5 that polysubstance use among people who use stimulants contributes to worse health outcomes and increased care utilization,6 and that receipt of treatment for StUD decreased significantly during the COVID-19 pandemic and has not yet returned to pre-pandemic levels.7
In the context of an ongoing overdose crisis and the resulting increased focus on opioid use among researchers, clinical leaders and policymakers,8 much research and clinical and policy interventions have focused on patients with opioid use disorder (OUD). For example, research on co-occurring disorders has tended to focus on OUD-specific services, and suggests that stimulant use/use disorder negatively impacts receipt of OUD treatment medications.9 However, it is unclear how co-occurring OUD may impact receipt of treatment for StUD. It is also unclear whether and how the characteristics, treatment receipt and hospitalization of patients with StUD—a group that has been paid relatively less attention but has also experienced increased risk of overdose—differ from patients with OUD. Additionally, little research has reported rates of treatment receipt and hospitalization among large samples of patients with StUD.4,7 Examining these questions can help inform efforts to address stimulant-related morbidity and mortality as researchers, clinical leaders and policy makers broaden their focus from opioids to address the evolving substance use landscape.
As the largest integrated healthcare system and largest provider of substance use disorder (SUD) treatment in the country, the VHA is an important setting in which to answer these questions. This study aimed to compare patient characteristics, SUD treatment receipt and hospitalization among patients with StUD without OUD, co-occurring StUD and OUD, and OUD without StUD in the national VHA.
METHODS
Data Source and Study Sample
Data were extracted from a repository of VHA electronic health record (EHR) data (the Corporate Data Warehouse).10 The study sample included patients across the national VHA with ≥1 outpatient or inpatient visit from March 1, 2020 to February 28, 2021 with an StUD and/or OUD diagnosis (primary or secondary). StUD and OUD diagnoses were defined using International Classification of Disease, 10th Revision, Clinical Modification (ICD-10-CM) codes (Appendix). Each patient’s first visit during the study period was considered the index visit.
Measures
Measure definitions that include ICD codes, clinic stop codes (VHA EHR codes indicating a visit to a specific clinical setting) or patient treatment file (PTF) codes are included in the Appendix.
Comparison Groups
As patients with co-occurring StUD and OUD likely differ from those with only one of the two conditions, we compared 1) patients who had StUD without OUD to those who had co-occurring StUD and OUD (StUD+OUD) and 2) patients who had StUD without OUD to those who had OUD without StUD.
Other Patient Characteristics
Other patient characteristics were assessed based on EHR documentation on the date of the index visit or in the prior year (including the date of the index visit). These included age, sex, race, ethnicity, rurality of patient residence based on Rural-Urban Commuting Area codes,11 homelessness/housing instability based on ICD and clinic stop codes,12 VHA eligibility status, other SUDs including alcohol use disorder, cannabis use disorder, and other drug use disorder (sedative, hallucinogen, inhalant, and/or other psychoactive substance), mental health diagnoses including depressive disorder, post-traumatic stress disorder (PTSD), anxiety disorder, and serious mental illness (bipolar, schizophrenia and/or psychosis), and number of Elixhauser comorbid conditions.13 VHA eligibility status measures eligibility for VHA care and is an indirect proxy for socioeconomic status, both of which likely impact service utilization. Having service connection means that veterans are eligible for lower-cost or cost-free care due to military service-connected disability, and lack of service connection reflects other reasons for eligibility such as low income.14,15
Outcome Variables
Outpatient SUD treatment was defined as having a clinic stop code for outpatient specialty SUD treatment in the year following the index visit (including the date of the index visit). Residential SUD treatment was defined as having a clinic stop code for residential SUD treatment in the year following the index visit (including the date of the index visit). For patients with StUD, these definitions included a primary or secondary StUD diagnosis associated with the visit; for patients with OUD without StUD these definitions included a primary or secondary OUD diagnosis associated with the visit. Any specialty SUD treatment was defined as having an outpatient and/or residential treatment visit in the year following the index visit. Medical hospitalization, surgical hospitalization, and psychiatric hospitalization were defined as having a hospitalization with a relevant PTF code (indication of treating specialty) in the year following the index visit (including the date of the index visit). Any hospitalization was defined as having a medical, surgical and/or psychiatric hospitalization in the year following the index visit.
Analyses
We first described patient characteristics and compared characteristics across the comparison groups as described above using chi-square tests (t-test for continuous age). We then described treatment receipt and hospitalization and compared outcomes across the comparison groups as described above using chi-square tests (t-test for count of SUD treatment visits). Finally, we fit generalized linear models with a logit link function and generalized estimating equation (GEE) to examine associations for 1) receipt of outpatient SUD treatment, 2) receipt of residential SUD treatment, 3) receipt of any specialty SUD treatment, and 4) any hospitalization. These models compared 1) patients who had StUD without OUD to those who had StUD+OUD and 2) patients who had StUD without OUD to those who had OUD without StUD. Models were clustered by VHA facility to account for correlation within facilities,16,17 and were adjusted for all patient characteristics described above which were considered potential confounders of these associations. Due to the large sample size, in addition to presenting confidence intervals (CIs) we also converted odds ratios (ORs) to standardized effect sizes (Cohen’s d) to examine the magnitude of effects.18 We first converted ORs<1 to positive values (1/OR),19 then calculated Cohen’s d using the formula ln(OR)/(π/√3).20 We interpreted a Cohen’s d of 0.2 as a small effect, 0.5 as a medium effect, and 0.8 as a large effect.18
All analyses were conducted in SAS® Enterprise Guide Software, Version 7.1.21 The VA Ann Arbor Healthcare System Institutional Review Board determined this study to be exempt from review.
RESULTS
Patient characteristics are described in Table 1. Among 132,273 VHA patients with StUD and/or OUD, 19,434 (14.7%) had StUD+OUD, 66,778 (50.5%) had StUD without OUD, and 46,061 (34.8%) had OUD without StUD. Patients with StUD without OUD were older and more frequently Hispanic than patients with StUD+OUD, and they were about the same age and less frequently Hispanic than patients with OUD without StUD. Compared to patients with OUD (with or without StUD), a much larger proportion of patients with StUD without OUD were Black and smaller proportions were female, White, service connected 50–100%, living in rural areas, and had anxiety. Housing instability, alcohol use disorder, cannabis use disorder, other drug use disorder, depression, post-traumatic stress disorder, serious mental illness, and ≥3 Elixhauser comorbidities were most common among patients with StUD+OUD, slightly less common among patients with StUD without OUD, and least common among patients with OUD without StUD.
Table 1.
Descriptive comparison of patient characteristics among VHA patients with StUD and/or OUD (N=132,273)
| StUD+OUD (n=19,434) n (%) |
StUD without OUD (n=66,778) n (%) |
p-valuea | OUD without StUD (n=46,061) n (%) |
p-valueb | |
|---|---|---|---|---|---|
| Age [mean(sd)] | 51.01 (13.52) | 55.81 (12.42) | <0.001 | 55.65 (14.65) | 0.054 |
| Age group | <0.001 | <0.001 | |||
| 18–29 | 518 (2.7) | 1,606 (2.4) | 820 (1.8) | ||
| 30–44 | 6,930 (35.7) | 12,503 (18.7) | 12,453 (27.0) | ||
| 45–64 | 8,384 (43.1) | 35,660 (53.4) | 17,039 (37.0) | ||
| 65+ | 3,602 (18.5) | 17,009 (25.5) | 15,749 (34.2) | ||
| Sex | 0.009 | <0.001 | |||
| Female | 1,510 (7.8) | 4,815 (7.2) | 3,862 (8.4) | ||
| Male | 17,924 (92.2) | 61,963 (92.8) | 42,199 (91.6) | ||
| Race | <0.001 | <0.001 | |||
| American Indian/Alaska Native | 177 (0.9) | 564 (0.8) | 433 (0.9) | ||
| Asian/Pacific Islander | 198 (1.0) | 1,004 (1.5) | 454 (1.0) | ||
| Black | 5,177 (26.6) | 31,909 (47.8) | 6,594 (14.3) | ||
| White | 12,710 (65.4) | 28,939 (43.3) | 35,427 (76.9) | ||
| Unknown | 1,172 (6.0) | 4,362 (6.5) | 3,153 (6.8) | ||
| Ethnicity | <0.001 | <0.001 | |||
| Hispanic | 1,270 (6.5) | 4,874 (7.3) | 5,676 (12.3) | ||
| Non-Hispanic | 18,164 (93.5) | 61,904 (92.7) | 39,318 (85.4) | ||
| VA eligibility status | <0.001 | <0.001 | |||
| Non-service connected | 5,636 (29.0) | 22,993 (34.4) | 14,376 (31.2) | ||
| Service connection <50% | 3,469 (17.9) | 13,102 (19.6) | 7,623 (16.6) | ||
| Service connection 50–100% | 10,293 (53.0) | 30,536 (45.7) | 23,994 (52.1) | ||
| Other/unknown | 36 (0.2) | 147 (0.2) | 68 (0.2) | ||
| Rurality | 0.064 | <0.001 | |||
| Urban | 17,275 (88.9) | 59,621 (89.3) | 39,318 (85.4) | ||
| Rural | 1,596 (8.2) | 5,154 (7.7) | 5,676 (12.3) | ||
| Unknown | 563 (2.9) | 2,003 (3.0) | 1,067 (2.3) | ||
| Homelessness/housing instability | 8,107 (41.7) | 23,996 (35.9) | <0.001 | 5,968 (13.0) | <0.001 |
| Alcohol use disorder | 12,658 (65.1) | 39,631 (59.4) | <0.001 | 12,076 (26.2) | <0.001 |
| Cannabis use disorder | 5,430 (27.9) | 12,887 (19.3) | <0.001 | 3,029 (6.6) | <0.001 |
| Other drug use disorderc | 8,503 (43.8) | 13,523 (20.3) | <0.001 | 5,640 (12.2) | <0.001 |
| Depressive disorder | 12,352 (63.6) | 35,178 (52.7) | <0.001 | 20,750 (45.1) | <0.001 |
| Post-traumatic stress disorder | 10,371 (53.4) | 25,877 (38.8) | <0.001 | 17,560 (38.1) | 0.033 |
| Anxiety disorder | 8,901 (45.8) | 20,995 (31.4) | <0.001 | 15,280 (33.2) | <0.001 |
| Serious mental illnessd | 6,130 (31.5) | 19,167 (28.7) | <0.001 | 6,507 (14.1) | <0.001 |
| ≥3 Elixhauser comorbiditiese | 15,134 (77.9) | 51,035 (76.4) | <0.001 | 23,887 (51.9) | <0.001 |
OUD = opioid use disorder; StUD = stimulant use disorder; VHA = Veterans Health Administration
p-value from chi-square test comparing “StUD+OUD” group to “StUD without OUD” group
p-value from chi-square test comparing “StUD without OUD” group to “OUD without StUD” group
Includes sedative, hallucinogen, inhalant, and/or other psychoactive substance
Includes bipolar disorder, psychosis and/or schizophrenia
Excluding StUD and OUD
Unadjusted comparisons of treatment receipt and hospitalization are presented in Table 2. All types of SUD treatment and all types of hospitalizations were less common and the mean number of SUD treatment visits was lower among patients with StUD without OUD compared to those with StUD+OUD. Receipt of outpatient SUD treatment and any specialty SUD treatment were less common among patients with StUD without OUD compared to those with OUD without StUD, but receipt of residential SUD treatment was more common and the mean number of SUD treatment visits was higher. All types of hospitalizations were more common among patients with StUD without OUD compared to those with OUD without StUD. Notably, 19.8% of patients with StUD without OUD were hospitalized during the 1-year follow-up period compared to 9.5% among patients with OUD without StUD.
Table 2.
Descriptive comparison of treatment receipt and hospitalization among VHA patients with StUD and/or OUD (N=132,273)
| Outcome (within 1 year following index visit) | StUD+OUD (n=19,434) n (%) |
StUD without OUD (n=66,778) n (%) |
p-valuea | OUD without StUD (n=46,061) n (%) |
p-valueb |
|---|---|---|---|---|---|
| Outpatient SUD treatmentc | 11,124 (57.2) | 24,164 (36.2) | <.0001 | 20,286 (44.0) | <.0001 |
| Residential SUD treatmentc | 3,871 (19.9) | 8,691 (13.0) | <.0001 | 2,038 (4.4) | <.0001 |
| Any specialty SUD treatmentc,d | 19,434 (62.9) | 26,987 (40.4) | <.0001 | 20,815 (45.2) | <.0001 |
| Number of SUD treatment visitsc,d [mean (SD)] |
12.81 (29.8) | 8.60 (25.5) | <.0001 | 8.47 (21.7) | 0.008 |
| Medical hospitalization | 1,812 (9.3) | 5,798 (8.7) | 0.006 | 2,470 (5.4) | <.0001 |
| Surgical hospitalization | 368 (1.9) | 997 (1.5) | <.0001 | 539 (1.2) | <.0001 |
| Psychiatric hospitalization | 3,440 (17.7) | 8,365 (12.5) | <.0001 | 1,872 (4.1) | <.0001 |
| Any hospitalization | 4,741 (24.4) | 13,234 (19.8) | <.0001 | 4,370 (9.5) | <.0001 |
OUD = opioid use disorder; SD = standard deviation; StUD = stimulant use disorder; VHA = Veterans Health Administration
p-value from chi-square test comparing “StUD+OUD” group to “StUD without OUD” group
p-value from chi-square test comparing “StUD without OUD” group to “OUD without StUD” group
For “StUD+OUD” and “StUD without OUD” groups, SUD treatment defined as a visit with a StUD diagnosis (primary or secondary); for “OUD without StUD” group, SUD treatment was defined as a visit with an OUD diagnosis (primary or secondary)
Including both outpatient and residential treatment
Results from regression models adjusted for patient sociodemographic and clinical characteristics are presented in Table 3. Compared to patients with StUD+OUD, patients with StUD without OUD were significantly less likely to have outpatient SUD treatment (adjusted OR [aOR] 0.49, 95% CI 0.47–0.50), residential SUD treatment (aOR 0.83, 95% CI 0.79–0.87), any specialty SUD treatment (aOR 0.47, 95% CI 0.46–0.49), and any hospitalization (aOR 0.94, 95% CI 0.90–0.98); effect sizes for outpatient SUD treatment and any specialty SUD treatment were between small and medium (Cohen’s d 0.39 and 0.42, respectively) and effect sizes for residential SUD treatment and any hospitalization were negligible (Cohen’s d 0.10 and 0.03, respectively). Compared to patients with OUD without StUD, patients with StUD without OUD were significantly less likely to have outpatient SUD treatment (aOR 0.51, 95% CI 0.49–0.52) and any specialty SUD treatment (aOR 0.56, 95% CI 0.54–0.58) and were significantly more likely to have residential SUD treatment (aOR 2.18, 95% CI 2.05–2.30) and any hospitalization (aOR 1.62, 95% CI 1.56–1.69); effect sizes for all of these associations were between small and medium (Cohen’s d ranged from 0.27 to 0.43).
Table 3.
Adjusted comparison of treatment receipt and hospitalization among VHA patients with StUD and/or OUD (N=132,273)
| Outcome (within 1 year following index visit) | aORa for StUD without OUD (ref: StUD+OUD) | 95% CI | Cohen’s db | aORa for StUD without OUD (ref: OUD without StUD) | 95% CI | Cohen’s db |
|---|---|---|---|---|---|---|
| Outpatient SUD treatmentc | 0.49 | (0.47, 0.50) | 0.39 | 0.51 | (0.49, 0.52) | 0.37 |
| Residential SUD treatmentc | 0.83 | (0.79, 0.87) | 0.10 | 2.18 | (2.05, 2.30) | 0.43 |
| Any specialty SUD treatmentc,d | 0.47 | (0.46, 0.49) | 0.42 | 0.56 | (0.54, 0.58) | 0.32 |
| Any hospitalization | 0.94 | (0.90, 0.98) | 0.03 | 1.62 | (1.56,1.69) | 0.27 |
aOR = adjusted odds ratio; CI = confidence interval; OUD = opioid use disorder; StUD = stimulant use disorder; VHA = Veterans Health Administration
Adjusted for age, sex, race, ethnicity, VA eligibility status, rurality, homelessness/housing instability, alcohol use disorder, cannabis use disorder, other drug use disorder, depressive disorder, post-traumatic stress disorder, anxiety disorder, serious mental illness, ≥3 Elixhauser comorbidities
Cohen’s d of 0.2 considered small effect size; 0.5 considered medium effect size; 0.8 considered large effect size
For “StUD+OUD” and “StUD without OUD” groups, SUD treatment defined as a visit with an StUD diagnosis (primary or secondary); for “OUD without StUD” group, SUD treatment was defined as a visit with an OUD diagnosis (primary or secondary)
Including both outpatient and residential treatment
DISCUSSION
This study of VHA patients with StUD and/or OUD found several demographic and clinical differences across patient groups—in particular, almost half of patients with StUD without OUD were Black in contrast to much smaller proportions in the other groups. Housing instability and most comorbidities were most common among patients with StUD+OUD, slightly less common among patients with StUD without OUD, and least common among patients with OUD without StUD. Overall, we found that patients with StUD without OUD were similar to patients with StUD+OUD with respect to high hospitalization rates, but were less likely to receive SUD treatment, specifically outpatient treatment. Compared to patients with OUD without StUD, those with StUD without OUD were less likely to receive any treatment or outpatient treatment but more likely to receive residential treatment and more likely to be hospitalized.
While patients with StUD may be more likely to receive residential SUD treatment than patients with OUD, they appear to be less likely to receive any specialty SUD treatment or outpatient SUD treatment (which is more widely available than residential treatment). This is concerning as effective treatments for StUD (e.g., contingency management) are currently typically only provided in specialty SUD care settings.22 Though we adjusted for housing instability and mental and physical comorbidities in regression analyses, increased medical complexity and social stressors among patients with StUD may create more barriers to engaging in outpatient SUD care.23 It is also possible that patients with OUD are more likely to engage in specialty SUD treatment because, unlike for StUD, there are multiple approved pharmacologic treatments for OUD.24 Additionally, the existence of multiple VHA initiatives focused on increasing treatment of OUD25–27 and an increased nationwide focus on addressing opioid use may be increasing treatment engagement among patients with OUD relative to patients with other drug use disorders who do not have OUD. Patients with StUD+OUD had the highest treatment receipt of the groups, and this may be partly driven by increased clinical severity among patients with multiple SUDs.
Patients with StUD without OUD were more likely to be hospitalized than patients with OUD without StUD, and incidence of next-year hospitalization was notably high among patients with StUD (20.8% for patients with StUD with or without OUD), with slightly higher incidence among those with StUD+OUD compared to those with only StUD. Most hospitalizations among patients with StUD (with or without OUD) were psychiatric hospitalizations, potentially reflecting psychiatric symptoms (e.g., psychosis, suicidal ideation, anxiety) associated with stimulant use and withdrawal that can be challenging to manage.28 Efforts to mitigate hospitalization among patients with StUD should include overdose prevention interventions (e.g., naloxone distribution, overdose prevention education),29 particularly given the sharp increase in overdoses involving both stimulants and opioids.30 These efforts should also include care that more effectively addresses the complex clinical needs of patients with StUD (e.g., improving care for people with multiple substance use disorders and/or co-occurring mental health conditions, improving management of psychiatric symptoms, suicide prevention interventions).31–33
Efforts that are specifically focused on engaging patients in StUD treatment are also needed. This work may draw on lessons learned from OUD treatment engagement efforts, while keeping in mind important differences between the patient populations and the evidence-based treatments that are available for each condition. StUD-focused efforts should take into consideration the high level of comorbidities and hospitalizations—particularly psychiatric hospitalizations—in this population. This may create barriers to treatment engagement that need to be overcome (e.g., through better coordination of mental health and SUD care33) but may also create opportunities for outreach and treatment linkage (e.g., improving linkage to SUD treatment for patients with StUD who have been hospitalized34). Other means of improving access to StUD treatment include increasing the availability of contingency management both within and outside of specialty SUD care settings (including via telehealth),22,35 and prioritizing research on pharmacologic treatment for StUD.36 Like all efforts to expand access to health services, these efforts should seek to address systemic racism which may create barriers to care for racially minoritized patients,37 who make up a much larger proportion of the VHA patient population with StUD than the population with OUD.
This study has limitations. Associations found in this observational study may have been impacted by residual confounding and cannot be interpreted as causal. ICD codes may have been applied inaccurately or may not measure StUD/OUD for patients who did not have their condition documented or diagnosed.38,39 Additionally, these data do not capture SUD treatment and hospitalization that may have occurred outside of the VHA system. Though we adjusted for mental and physical comorbidities, we were unable to measure and adjust for other indicators of clinical severity such as SUD severity level, specific drug types, and routes of drug administration. Finally, though it is important to examine these research questions in the VHA—the country’s largest integrated healthcare system and largest provider of SUD care—findings may have limited generalizability to non-VHA settings or veterans who do not receive care in the VHA.
CONCLUSIONS
This study found that among VHA patients with StUD and/or OUD, those with StUD without OUD had a substantially higher proportion of Black patients, and housing instability and most comorbidities were most common among patients with co-occurring StUD and OUD, slightly less common among patients with StUD without OUD, and least common among patients with OUD without StUD. Patients with StUD (with or without OUD) had high rates of hospitalization, especially psychiatric hospitalization, and patients with StUD without OUD were less likely to receive SUD treatment. Efforts are needed that focus on improving care, reducing the need for acute care, and increasing treatment receipt for patients with StUD.
Supplementary Material
Sources of Support/Funding:
This research was supported by funding from VA Health Services Research & Development (HSR&D CDA18-008) and from the National Institute on Drug Abuse (NIDA R01DA05759). This material is based upon work done as part of the VA Advanced Fellowship Program in HSR&D supported by the Office of Academic Affiliations, US Department of Veterans Affairs. Funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. The opinions expressed in this work are the authors’ and do not necessarily reflect those of the institutions, funders, the National Institutes of Health, the Department of Veterans Affairs, or the United States Government.
Conflicts of Interest:
Dr. Lin consults on telehealth for substance use disorder treatment for Providers Clinical Support System with funding from the Substance Abuse and Mental Health Services Administration, and for National Center for Quality Assurance with funding from Alkermes. No other disclosures are reported.
Footnotes
Preliminary findings from this study were presented at the 2023 College on Problems of Drug Dependence Annual Meeting and the 2023 Addiction Health Services Research Conference.
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