ACA Dependent Coverage Extension and Young Adults’ Substance-Associated ED Visits

ABSTRACT

Objectives: The Affordable Care Act (ACA), enacted in 2010, aimed to improve health insurance coverage and access to care, notably through a provision extending dependent coverage up to age 26 years. This study investigates the ACA’s impact on substance use disorder (SUD)–associated emergency department (ED) visits among young adults aged 23 to 29 years.

Study Design: A quasi-experimental study analyzed opioid- and alcohol-associated ED visits and inpatient admissions among young adults (aged 23-25 [treatment] vs 27-29 [comparison] years) using 2007-2019 Nationwide Emergency Department Sample data.

Methods: A difference-in-differences approach assessed the ACA’s impact, adjusting for covariates including sex, comorbidities, payer source, income, residence, and hospital region. Generalized linear models estimated adjusted ORs with 95% CIs, ensuring robust analysis of the ACA’s effects on substance-related health care utilization.

Results: Opioid-associated ED visits had no change between the treatment and comparison groups, whereas alcohol-associated ED visits declined more for the treatment group after the ACA (OR, 0.841; 95% CI, 0.828-0.855). No changes in inpatient admissions among opioid- or alcohol-associated visits, respectively, were seen between the 2 groups.

Conclusions: Our findings indicate that the ACA’s implementation led to mixed effects on substance-associated health care utilization among young adults, with reduced alcohol-associated visits in the treatment group but unchanged discrepancies in opioid-associated ED visits and inpatient admissions between the 2 groups. Further research is warranted to explore state-level variations and population-level substance use trends along with continuous monitoring to inform interventions addressing substance-associated public health challenges.

Am J Manag Care. 2025;31(9):In Press

Takeaway Points

• This study examines how the Affordable Care Act (ACA) impacted substance-associated emergency department (ED) visits among young adults, highlighting its effects on health care utilization and policy implications.
• Extending dependent insurance coverage under the ACA led to a decline in alcohol-associated ED visits, underscoring the importance of continuous insurance access.
• No significant change in opioid-associated ED visits suggests a need for targeted interventions beyond insurance expansion.
• Employers and policy makers should support comprehensive health benefits, including mental health and substance use treatment, to improve workforce well-being.
• Ongoing evaluation of health care policies is crucial to addressing gaps in substance use disorder treatment.

The Affordable Care Act (ACA), which was enacted in 2010, was a transformative health policy initiative aimed at expanding health insurance coverage and improving access to care in the US, particularly for young adults. One of its key provisions allowed young adults to remain on their parents’ health insurance plans until age 26 years, addressing a critical gap in coverage for this demographic.¹ Prior to the ACA, the uninsured rate was approximately 29% among individuals aged 18 to 24 years and approximately 27% among those aged 25 to 34 years.² Lack of health care access can force young adults to rely on emergency departments (EDs) for their medical needs, including behavioral health issues such as substance use disorders (SUDs), due to limited access to primary and preventive health care services.³ The intention behind extending dependent coverage was to improve access to a range of health services, including outpatient treatment for SUDs, which have become increasingly prevalent among young adults.⁴

Over the past 2 decades, the rise in substance use and dependence has emerged as a pressing public health concern in the US, with SUDs affecting more than 20 million Americans annually.^5,6 Younger adults aged 18 to 35 years are at heightened risk for risky substance use behaviors, including opioid use, excessive alcohol consumption, and recreational drug use.⁷ This age group is also significantly impacted by the ongoing opioid epidemic, resulting in a dramatic increase in opioid-related ED visits, which quadrupled between 1993 and 2010.⁸ The consequences of SUDs extend beyond individual health, including their contribution to increased morbidity and mortality rates exemplified by the 106,000 overdose deaths recorded in 2021 and the substantial economic burden on society.^6,9

Young adults with SUDs frequently utilize ED services, often as a safety net because of the barriers to accessing ambulatory care. Research indicates that individuals with SUDs utilize ED services at rates 50% to 100% higher than those without such disorders.¹⁰ The proportion of ED visits associated with mental health and substance use has risen markedly, from 4% to 6% in the early 1990s to an estimated 12% by 2007.¹¹ Between 2009 and 2017, the number of annual ED visits related to opioids and alcohol surged from 73,262 to 1,070,747, with a notable increase among young adults aged 21 to 29 years.^12,13 Some of these visits may have been preventable, including through better access to outpatient care, but numerous barriers persist, including a shortage of providers who accept public insurance, stigma, and insufficient mental health and SUD resources.^14,15 The ACA’s dependent coverage extension aimed to alleviate financial barriers, yet gaps in care for SUDs remain a challenge, as highlighted by literature examining the ACA’s effects on behavioral health and substance use outcomes.¹⁴

Despite the extension improving insurance coverage, the relationship between the ACA dependent coverage provision and ED utilization for SUDs is complex and multifaceted. Although the extension may enhance financial access to care, other structural and systemic barriers persist, particularly for populations with high unmet needs.¹⁶ Such challenges complicate the task of hypothesizing the ACA’s impact on ED visits a priori, as the effects of improved insurance coverage must be considered alongside the broader health care landscape.¹⁷

Sociodemographic disparities further complicate the landscape of ED visits for SUDs. Young adults in rural areas, those without insurance, and individuals from lower-income backgrounds are more likely to seek care in EDs for substance-related issues.¹⁸ Compared with their privately insured counterparts, Medicaid and uninsured patients tend to visit EDs more frequently for chronic conditions, mental health disorders, and SUDs.¹⁹ In 2017, more than 10.7 million ED visits were recorded for mental health or substance use issues, predominantly among middle-aged adults with low socioeconomic status.^12,20,21 Although the ACA’s dependent coverage extension has been associated with improved access to care, the impact on substance use–related ED visits among young adults remains underexplored.

Study findings have shown that the ACA’s Medicaid expansion significantly reduced all-cause mortality, including deaths related to SUDs.²² However, research examining the effects of the dependent coverage provision on the highest-risk age group for SUDs (21-29 years) is limited. This gap in the literature raises questions about the complexities of access to care for young adults with SUDs, particularly in light of persistent barriers such as provider shortages and insurance limitations.^14,15 Understanding how the ACA provision influences utilization of emergency services for young adult substance use is critical. Using the Nationwide Emergency Department Sample (NEDS), this study aimed to characterize the impact of the ACA dependent coverage extension on ED use among young adults (aged 23-29 years) for (1) alcohol use and (2) opioid use. Results of this analysis have important implications for health policy and practice.

METHODS

Study Design and Data

NEDS, a deidentified data set, represents 20% of all US ED visits.²³ NEDS data are collected annually; this analysis used the 2007, 2009, 2011, 2013, 2015, 2018, and 2019 data. This quasi-experimental study included an intervention group (aged 23-25 years) and a comparison group (aged 27-29 years). Those aged 26 years were excluded per prior research² due to classification challenges. Opioid- and alcohol-associated ED visits were compared pre-ACA (2007-2009) and post ACA (2011-2019) because of their high prevalence and sensitivity to ACA-driven changes in access to care. Other substances were excluded due to lower prevalence and limited policy impact evidence. Of 19,856,756 total ED visits included in analyses, 164,929 were opioid associated and 285,578 were alcohol associated. The University of Nevada, Las Vegas Institutional Review Board deemed the study exempt due to the data set’s deidentified, public nature.

Measures

Four binary dependent variables investigated in this study were ED visits associated with use of opioids and alcohol, respectively, and admission to inpatient care after the opioid- or alcohol-associated ED visit.²⁴ We utilized both principal and secondary diagnoses of opioid- and alcohol-associated ED visits in patients aged 23 to 25 years and 27 to 29 years using the International Classification of Diseases, Ninth and Tenth Revisions, Clinical Modification.^25,26 Admission to inpatient care can indicate ED visits with relatively severe clinical conditions as opposed to ED visits that were unnecessary or for ambulatory care–sensitive conditions.^27,28

The ACA and treatment were the 2 independent variables of interest. The ACA was a dichotomous variable, with 0 indicating pre–ACA implementation (2007-2009) and 1 indicating post ACA implementation (2011-2019). Treatment was a dichotomous variable, with 1 indicating the treatment group (aged 23-25 years; those affected by the ACA dependent coverage extension) and 0 indicating the comparison group (aged 27-29 years; those not affected by the ACA dependent coverage extension), consistent with previous research.² The control variables or covariates in multivariable analyses included sex (female, male [reference]), the number of diagnoses (comorbidities), payer source (Medicaid, uninsured, private insurance [reference]),²⁹ median income by zip code in quartiles (0-25th percentile, 26th-50th percentile, 51st-75th percentile, 76th-100th percentile [reference]),³⁰ patient residence location (rural [ie, not metropolitan or micropolitan counties], nonrural [reference]),³¹ and US region of hospital location (Northeast, Midwest, South, West [reference]).³²

Statistical Analysis

A difference-in-differences (DID) analysis was conducted to examine impacts of the ACA dependent coverage extension on substance use–associated ED visits, controlling for covariates. We included the covariates listed earlier in the DID analysis and adjusted for potential differences in observed characteristics between the treatment (aged 23-25 years) and comparison (aged 27-29 years) groups that could introduce bias in estimating ED utilization trends. These covariates were selected to control for systematic differences between groups that could influence health care access, health status, and substance use behaviors. Although a well-balanced DID design does not theoretically require covariate adjustment if the parallel trends assumption holds, the inclusion of covariates serves as a robustness measure to mitigate residual confounding and enhance the validity of the findings. The DID assumption of the parallel trends was tested before the analysis. First, we used data on the outcomes from both treatment and comparison groups before the ACA was implemented. Second, we tested whether the trends in outcomes leading up to the ACA statistically differed between the treatment and comparison groups³³ by restricting our attention to the prior ACA data and then examining the interaction between the number of years before ACA and the treatment variable on the dependent variables; this yielded insignificant regression coefficients of the interaction term, with P values of .4635 for opioid use, .7906 for alcohol use, .0593 for inpatient admissions among opioid users, and .6491 for inpatient admissions for alcohol users.

The DID estimator (δ) is:

δ = (Y_{treatment post} – Y_{treatment pre}) – (Y_{comparison post} – Y_{comparison pre}),

where δ represents effect of the ACA on the average outcome of Y, Y shows average outcomes, treatment represents a group (aged 23-25 years) exposed to ACA, comparison represents a group (aged 27-29 years) not exposed to ACA, pre represents before ACA implementation, and post represents after ACA implementation. The DID estimate is equal to 0 if there is no association between policy implementation and subsequent outcomes. In the econometric framework, for individual i in treatment group j at time t with 2 groups (treatment and comparison group) and 2 time periods (pre- and post ACA), baseline DID models of this study take the form:

Y_ijt = β₀ + β₁Post_it + β₂Treat_ij + β₃(Treat_ij × Post_it) + X_ijt + ε_ijt,

where Y_ijt represents an outcome variable for a dependent variable for patient i of treatment group j in time t; Post_it is a dummy variable for whether a patient occurred in the post-ACA period; Treat_ij is a dummy variable indicating the value of 1 if a patient is in the treatment group and 0 otherwise; β₃represents impact of the ACA on changes in outcomes; X_ijt is a vector of fixed effects of control variables for sex, comorbidity, and median income by zip code; and ε_ijt is the error term.

The impact of the ACA was observed as β₃ of the interaction between treatment and post. A generalized linear model was selected for estimating β₃. Given the fact that all discharges in a hospital were contained in the data set if the hospital was selected into the NEDS, the generalized mixed model using hospital as a random effect was eventually utilized to take into account cluster effects among discharges within each hospital. Several sensitivity analyses were conducted, including the comparison between models with and without the time (year) fixed effect and the comparison of the weighted logistic regression model against the generalized mixed model. Sensitivity analysis results were consistent in terms of the post-ACA effects on the 2 groups (shown in the eAppendix [available at ajmc.com]). Results generated from the generalized mixed model based on equation 2 are presented using adjusted ORs with 95% CIs in the Results section.

RESULTS

Table 1 presents sociodemographic characteristics of patients aged 23 to 25 years (treatment) and 27 to 29 years (comparison) who had ED visits associated with use of opioid and alcohol before and after ACA implementation. Approximately 60% of ED visitors were female, and the comparison group had a slightly higher number of diagnoses than the treatment group in both the pre- and post-ACA periods. Medicaid coverage increased and uninsurance declined in the post-ACA period for both the treatment and comparison groups, and approximately 12% of the patients resided in rural areas.

Among ED visits, 0.52% for the treatment group and 0.58% for the comparison group were associated with opioid use prior to the ACA vs rates of 0.84% and 1.02%, respectively, after ACA implementation. Furthermore, 1.87% of ED visits in the treatment group and 1.99% of ED visits in the comparison group were associated with use of alcohol prior to the ACA, whereas the rates were 1.07% and 1.39%, respectively, post ACA. In addition, among patients associated with opioid use, 38.15% in the treatment group and 40.63% in the comparison group were admitted to inpatient care before the ACA, and 27.55% and 31.27%, respectively, were admitted to inpatient care after the ACA. Among patients associated with alcohol use, 24.55% and 29.59% were admitted to inpatient care in the treatment and comparison groups, respectively, before the ACA, whereas 20.73% and 25.44%, respectively, were admitted to inpatient care after the ACA.

Table 2 presents the results of the multivariable analysis. In the pre-ACA period, compared with the control group, the treatment group was less likely to visit the ED for opioid-associated reasons (OR, 0.920; 95% CI, 0.899-0.942). Post ACA, this difference was no longer statistically significant (OR, 1.013; 95% CI, 0.987-1.039), indicating that the ACA did not differentially impact opioid-associated ED visits across age groups. However, opioid-associated ED visits increased overall post ACA (OR, 1.263; 95% CI, 1.241-1.286).

The treatment group had lower odds of alcohol-related ED visits than the control group before the ACA (OR, 0.972; 95% CI, 0.960-0.985), and this disparity further increased post ACA (OR, 0.841; 95% CI, 0.828-0.855), suggesting a more pronounced reduction in alcohol-associated ED visits among the treatment group.

Among young adults whose ED visits were associated with opioids, the odds of inpatient admission were similar between the treatment and control groups before the ACA (OR, 1.012; 95% CI, 0.958-1.068), and this pattern remained unchanged post ACA. However, the ACA was associated with lower overall odds of inpatient admission for opioid-associated ED visits (OR, 0.326; 95% CI, 0.312-0.341), suggesting a shift in hospitalization trends.

Among young adults whose ED visits were associated with alcohol, the treatment group had lower odds of inpatient admissions compared with the control group before the ACA (OR, 0.871; 95% CI, 0.843-0.899). Post ACA, this difference remained unchanged (OR, 1.010; 95% CI, 0.956-1.055), indicating that the gap between the age groups remained similar. However, the ACA was associated with lower overall odds of inpatient admission for alcohol-associated ED visits (OR, 0.298; 95% CI, 0.289-0.307), suggesting a shift in hospitalization trends. Overall, the ACA was associated with reduced odds of inpatient admission for alcohol-associated ED visits among all young adults (aged 23-29 years).

DISCUSSION

Our findings suggest mixed effects of the ACA dependent coverage extension on substance use–associated ED visits, aligning with and diverging from prior research in nuanced ways.³⁴ The ACA’s dependent coverage provision aimed to improve young adults’ access to health care, and our results suggest that opioid-associated ED visits increased among all young adults (aged 23-29 years) following implementation, a trend that contrasts with earlier studies anticipating that expanded insurance coverage would reduce ED visits through improved access to preventive care and outpatient services.³⁵ This increase was not specific to the treatment group, as there was no significant interaction between age group and ACA period for opioid-related visits, suggesting that broader population trends—such as increased opioid availability and use—may be driving these findings.³⁶ Ongoing issues with the opioid epidemic, specifically fentanyl availability, may explain these findings because opioid-related deaths in the US significantly rose from 6.8 per 100,000 in 2010 to 25 per 100,000 in 2022.³⁷ Many of these cases involve overdose events requiring emergency hospitalization, contributing to higher inpatient admissions.³⁸

The results further suggest that the ACA dependent coverage extension had a differential effect on alcohol-associated ED visits. Before the ACA, young adults aged 23 to 25 years had significantly lower odds of an alcohol-associated ED visit than those aged 27 to 29 years. Following the ACA, this difference became more pronounced, with the treatment group showing further reductions in alcohol-associated ED visit odds relative to the comparison group. This suggests that alcohol use is influenced by social and environmental factors beyond insurance access.³⁹ The widening disparity post ACA may indicate a beneficial effect of dependent coverage on access to behavioral health services for alcohol use among young adults. However, the overall high volume of alcohol-associated ED visits across both age groups underscores the persistent burden of problematic alcohol use among young adults, suggesting that insurance expansion alone may be insufficient to address broader population-level drinking hazards.

Prior to the ACA, the treatment group had slightly lower odds of opioid-associated ED visits than the comparison group, but this gap waned post ACA, suggesting a convergence rather than a divergence in ED utilization patterns.³⁶ The treatment group, benefiting from dependent coverage and public health efforts, may have had improved access to care.⁴⁰ Meanwhile, the control group, less likely to gain insurance, faced persistent treatment barriers, leading to ongoing opioid-associated complications requiring ED utilization.⁴¹ These findings align with research indicating that insurance expansion improves access but does not uniformly reduce substance-related ED visits.³⁶

Opioid-associated inpatient admissions declined post ACA, suggesting that more patients presented to the ED with less severe conditions, which aligns somewhat with studies supporting utilization of earlier or outpatient-based care but contrasts with others reporting stable or increasing inpatient treatment needs.^42,43 The unchanged admission rates between groups pre- and post ACA indicate a uniform impact of ACA policies on inpatient care among young adults. Medicaid expansion and dependent coverage likely contributed to the decline in opioid-associated inpatient admissions by increasing access to outpatient services.⁴³ Before and during the early ACA years, opioid users often sought prescriptions in outpatient settings. By the mid-2010s, prescription drug monitoring programs (PDMPs) led to reduced prescribing, potentially increasing ED visits for drug-seeking and shifting users to illicitly obtaining opioids.^44,45 Although our data do not directly capture patient intent or prescription-seeking behavior, this broader policy context may explain why some patients presented without conditions warranting inpatient admission.

For alcohol-related ED visits, the treatment group had lower inpatient admission odds pre-ACA, with a similar gap post ACA, despite an overall decline, which is consistent with prior research.³⁹ The ACA likely reduced financial barriers to outpatient care, although structural and behavioral factors may still influence inpatient admissions.³⁹ Alcohol use patterns may be more responsive to insurance expansion than opioid use because they are less entangled with illicit drug markets and criminalization pressures.Hospitals may have also adopted alternative management strategies, such as observation units and community-based treatment, reducing inpatient admissions while addressing patient needs.⁴⁶ However, persistent inpatient demand underscores the need for expanded treatment access and improved care coordination.⁴⁷

By expanding insurance coverage, the ACA may have reduced reliance on EDs for alcohol- and opioid-related problems by enabling more outpatient care.⁴² Previously, uninsured patients in states such as Nevada may have accessed treatment through involuntary holds (eg, Legal 2000). Post ACA, improved insurance coverage likely facilitated voluntary treatment, potentially reducing substance-related ED visits. Future research should examine how expanded insurance coverage interacts with structural factors, such as availability of outpatient services, stigma, and socioeconomic barriers, to influence ED utilization patterns.³⁶ Researchers should also explore how state-level policy differences, such as Medicaid expansion timing or PDMP implementation, affected these trends.^44,45,48 Additionally, investigating demographic and geographic variations could reveal important disparities in how the ACA impacted different populations.⁴⁹

Limitations

These findings should be considered alongside key limitations. First, NEDS data lack patient race, ethnicity, and hospital location in certain years, potentially introducing bias and limiting geographic and demographic analyses.⁴⁹ Second, although Medicaid expansion status was included in models, variations in implementation may still affect results.⁴⁸ Third, state-level policy variations complicate assessments of the ACA’s impact, warranting future interrupted time series analyses. Fourth, interpreting the OR of the treatment-ACA interaction was challenging, so we focused on effect significance rather than magnitude.⁵⁰ Lastly, we could not adjust for factors such as education and income due to data limitations. We also acknowledge that we could not account for all contemporaneous factors, such as the rise of fentanyl and other synthetic opioids, which may contribute to increased opioid-associated ED admissions regardless of insurance status. Despite these constraints, the use of a comparison group and pre-post design strengthens our analysis.

CONCLUSIONS

Although the ACA’s dependent coverage provision did not differentially impact opioid-associated ED visits between the treatment and comparison groups, our findings indicate a greater reduction in alcohol-associated ED visits among young adults newly eligible for coverage (aged 23-25 years) compared with their slightly older peers. This age-specific decline in alcohol-associated ED use may reflect improved access to preventive or behavioral health services among insured young adults or shifting patterns in substance use behaviors in response to increased engagement with the health care system. These findings suggest that even modest expansions in coverage can yield important behavioral health benefits, particularly for substances such as alcohol that are often underrecognized in acute care settings. Future research should explore mechanisms driving this reduction—such as increased outpatient service utilization, earlier intervention for alcohol misuse, or changing perceptions of risk—and assess whether similar patterns emerge for other substance types or under subsequent health policy reforms. 

Author Affiliations: Department of Social and Behavioral Health (RRS, TG), Department of Healthcare Administration and Policy (CC), and Center for Health Disparities Research (JJS), School of Public Health, University of Nevada, Las Vegas, Las Vegas, NV.

Source of Funding: None.

Author Disclosures: The authors report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.

Authorship Information: Concept and design (RRS, JJS); acquisition of data (CC, JJS); analysis and interpretation of data (RRS, TG, JJS); drafting of the manuscript (RRS); critical revision of the manuscript for important intellectual content (TG, CC, JJS); statistical analysis (JJS); administrative, technical, or logistic support (TG, CC, JJS); and supervision (JJS).

Address Correspondence to: Jay J. Shen, PhD, University of Nevada, Las Vegas, 4700 S Maryland Pkwy, Las Vegas, NV 89154. Email: jay.shen@unlv.edu.

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