Using data from the nationally diverse All of Us Research Program (2018–2023), this study examined healthcare service utilization patterns among 19,423, adults with co-occurring substance use and mental health disorders (COD). Despite the complexity and elevated risk of COD, only 57.1% of participants received any healthcare during the study period. Counseling and therapy were the most used services, online healthcare showed a temporary surge during the COVID-19 pandemic, and medication/somatic service utilization remained stable throughout. Healthcare service utilization varied significantly by sociodemographic and structural determinants, including age, gender, income, insurance type, and disability status, highlighting persistent inequities in access and engagement.

The 57.1 % healthcare utilization proportion of this study cohort remains below the national estimate of 62.4 % among adults with COD, as reported by the 2023 National Survey on Drug Use and Health (Substance Abuse and Mental Health Services Administration, 2024b) and is consistent with prior national analyses documenting low and fragmented healthcare engagement in this population (Jones & McCance-Katz, 2019). Differences in measurement methodology may partly explain this gap: national estimates rely on self-reported service use, whereas the present study draws on EHR data that capture only documented encounters within participating systems. Individuals who accessed community-based or informal care outside of clinical settings may therefore not have been represented. Moreover, the All of Us cohort intentionally engages individuals historically under-represented in biomedical research, including individuals those from lower socioeconomic backgrounds (All of Us Research Program Investigators, 2019). Recent phenomic analyses of All of Us participants have also shown that the cohort differs systematically from the general U.S. population, indicating that findings from All of Us may not be fully generalizable to national patterns of COD healthcare utilization (Zeng et al., 2024).

Collectively, these findings emphasize persistent limitations in service engagement for people with COD and the need for stronger coordination across systems of care.

Counseling and therapy services emerged as the dominant healthcare approach, accounting for the largest share of utilization. This pattern aligns with prior work emphasizing the centrality of psychotherapy in behavioral health care (Flynn & Brown, 2008; Johansen & Sicker, 2022). The broad applicability of psychotherapy billing codes and the widespread availability of counseling services likely contribute to their prominence. Psychosocial counseling interventions remain the most empirically supported first-line healthcare services for both MHD and SUD, making them a common initial modality of care for individuals with COD (Azad et al., 2022; Carroll & Kiluk, 2017).

Beyond counseling, medication and somatic service utilization was stable throughout the study period, highlighting the continued importance of pharmacological interventions for managing symptoms of severe mental illness and substance use disorders (Iqbal et al., 2019; Simpson et al., 2021). More intensive services, such as detoxification, residential programs, and crisis intervention, were rarely utilized. This underutilization reflects persistent structural barriers, including cost, availability, and fragmentation between mental health and addiction systems (Foster et al., 2010; Priester et al., 2016). The separation of funding streams and licensing requirements may further inhibit access to integrated, high-intensity care (Priester et al., 2016).

High costs and limited geographic availability of residential programs also disproportionately burden low-income and rural populations, widening existing disparities (Lynch et al., 2024).

There were substantial shifts in temporal trends during the COVID-19 pandemic. Counseling and therapy services peaked in 2019 and subsequently declined, likely reflecting disruptions in in-person care delivery and the broader psychosocial strain of the pandemic. This trajectory mirrors national evidence documenting increased psychological distress and substance use during this period, which reshaped patterns of care-seeking (Czeisler et al., 2020). In contrast, online healthcare services surged in 2020 amid lockdowns and the rapid expansion of telehealth infrastructure, reflecting a temporary shift toward virtual modalities (Uscher-Pines et al., 2022). Despite this rise, online healthcare declined in subsequent years, suggesting that telehealth engagement may be difficult to sustain among individuals with COD. Barriers such as limited digital access, provider capacity, and challenges in delivering integrated dual-diagnosis care virtually likely contributed to this decline (Kisicki et al., 2022; Pham et al., 2025).

Findings revealed associations between several demographic and structural factors and healthcare utilization. Older adults were more likely to receive care, consistent with evidence showing lower utilization among younger populations despite their higher prevalence of COD (Dhinsa et al., 2023; Substance Abuse and Mental Health Services Administration, 2024b). This age pattern may also reflect differences in insurance coverage, because older adults are more likely to have stable health insurance, including Medicare, which increases access to behavioral health services compared with younger adults who experience higher rates of uninsurance (Bunch & Ketema, 2025). These differences in coverage and access may compound the challenges younger adults already face. Barriers for younger adults may include stigma, limited age-appropriate services, and insufficient outreach (James et al., 2024; Sterling et al., 2010).

Gender disparities were also evident: male participants and those with an unspecified gender designation had higher odds of receiving healthcare than female participants, contrasting with national trends of greater engagement among women (Dhinsa et al., 2023). Barriers such as childcare responsibilities, trauma histories, and stigma may restrict service use among women with COD (Harris et al., 2022; Rosen et al., 2004).

Socioeconomic status exerted a substantial influence on service utilization. Lower income was associated with reduced healthcare utilization, reinforcing the role of financial and systemic barriers in limiting access. This pattern aligns with evidence showing that low-income individuals face persistent cost-related and geographic obstacles to both mental health and substance use healthcare (Edlund et al., 2009; Kim & Cardemil, 2012). While some research suggests higher SUD healthcare rates among low-income groups due to targeted outreach, these dynamics may differ in COD populations, where access to integrated and continuous care remains constrained (Dhinsa et al., 2023).

Insurance coverage further shaped access. Participants with employer-sponsored or private insurance were significantly more likely to receive healthcare, whereas Medicaid recipients were less likely. This discrepancy may reflect state-level variation in Medicaid behavioral-health benefits, provider shortages, and administrative burdens that limit comprehensive coverage.

Differences in reimbursement rates and coverage for residential or intensive programs further restrict service availability, particularly for individuals with COD (Dickson-Gomez et al., 2022; Foster et al., 2010; Priester et al., 2016). Addressing these inequities will require policies that standardize and expand Medicaid behavioral-health benefits to ensure consistent, integrated care across states.

Disability status was positively associated with healthcare utilization, suggesting that individuals with more complex health needs may be more likely to access services. This finding aligns with prior evidence showing that adults with disabilities experience higher prevalence of MHD and SUD and have greater contact with healthcare systems, resulting in increased service utilization (Reif et al., 2022). However, despite higher engagement, many still encounter barriers such as accessibility challenges, provider stigma, and financial constraints, which may limit continuity and adequacy of care (Xie et al., 2022).