Healthcare utilization among adults with co-occurring substance use and mental health disorders (2018-2023): A study based on All of Us program

BackgroundCo-occurring substance use and mental health disorders (COD) represent a growing public health concern, yet healthcare utilization studies with a large sample size remain limited. This study examined healthcare utilization patterns and sociodemographic correlates among COD adults using data from the All of Us Research Program (2018-2023). MethodsElectronic health record data were analyzed for adults aged [≥]18 years with confirmed diagnoses of substance use and mental health disorders recorded on at least two occasions. Healthcare services were identified using the standardized Current Procedural Terminology and Healthcare Common Procedure Coding System codes and categorized into counseling and therapy, medication/somatic services, online or telehealth care, and other supportive modalities. Multivariable logistic regression was employed to assess sociodemographic and structural correlates of healthcare utilization. ResultsAmong 19,423 adults with COD, 57.1% received healthcare. Counseling and therapy accounted for the largest share of encounters, while online services surged in 2020 during the COVID-19 pandemic. Healthcare utilization was higher among older adults ([≥]65 years: aOR=1.52, 95%CI:1.29-1.78), males (aOR=1.19, 95%CI:1.12-1.26), individuals with disabilities (aOR=1.46, 95%CI:1.36-1.56), and those with employer-sponsored (aOR=1.22, 95%CI:1.10-1.36) or other private insurance (aOR=2.15, 95%CI:1.97-2.34). The level of healthcare utilization was lower among participants with lower income ([≤]$25,000: aOR=0.75, 95%CI:0.69-0.81) or Medicaid coverage (aOR=0.83, 95%CI:0.77-0.89). ConclusionsDespite high clinical need, healthcare utilization among adults with COD remains suboptimal and is shaped by structural inequities across income and insurance lines. Findings highlight the need to expand integrated healthcare services, strengthen Medicaid coverage, and sustain telehealth infrastructure to promote equitable, long-term engagement in care. Highlights{o} Individuals with co-occurring disorders continue to face low healthcare utilization. {o} Counseling and therapy were the major mode of care, while telehealth peaked during COVID-19. {o} Lower income and Medicaid coverage were tied to lower healthcare utilization. {o} Older adults and people with disabilities were more likely to use healthcare services. {o} Findings highlight the needs to expand integrated, equitable behavioral care.