Demographics and Health Insurance Coverage of Nonelderly Adults With Mental Illness and Substance Use Disorders in 2020

The pandemic has worsened underlying mental illness and substance use disorders, particularly for some subgroups, and challenges accessing treatment may have increased. In this issue brief, we use 2020 data from the National Survey on Drug Use and Health (NSDUH) to examine key characteristics, coverage and health status of nonelderly adults with mental illness or substance use disorders to help inform ongoing federal and state efforts to improve quality and expand access.

This analysis relies on the NSDUH definitions of mild, moderate, or serious mental illness using DSM-IV criteria. Those with serious mental illness (SMI) often have difficulties with daily living activities, comorbid conditions like substance use disorders and physical conditions, and in general, people with mental illness die earlier than those without. NSDUH uses DSM-V diagnostic criteria to assess the presence of substance use disorders. These disorders are categorized into mild, moderate, and severe groups depending on symptom severity. In addition to legal substances such as alcohol and sometimes marijuana, substance use disorders can also involve illicit substances such as opioids and cocaine. Due to the pandemic, NSDUH data is limited to the first and fourth quarter of 2020, with survey data collection shifting from in-person interviews to web-based surveys, so data cannot be compared to other years. Small sample sizes prevent subgroup analyses among the uninsured population.

Key findings include the following:

• Mental illness and substance use disorders affects one-third (64.5 million) of all nonelderly adults in 2020 and are most prevalent among young adults and White people. Other data and research point to worsening mental health for young adults and people of color during the pandemic. The lower rates among people of color may reflect underdiagnosis among these groups. Data show that women have higher rates of mental illness, while men have higher rates of substance use disorder.
• Most nonelderly adults with mental illness or substance use disorder are covered by private insurance (58%), but Medicaid enrollees are more likely to experience those conditions. Medicaid enrollees also have the highest overall prevalence of moderate to severe mental illness or substance use disorders.
• Among nonelderly adults with a moderate to severe mental illness or substance use disorder, Medicaid enrollees are more likely than those with private insurance to have chronic health conditions and to report fair or poor health.

What is the prevalence of mental illness and substance use disorders and what are the characteristics of people with these conditions?  

One-third (33%) of all nonelderly adults have a mental illness or substance use disorder.  Mental illness affects 23% (45.3 million) of nonelderly adults, with 11% having mild conditions, 6% moderate, and 6% severe conditions. Approximately 18% (34.7 million) of nonelderly adults experience some form of substance use disorder, with milder disorders (10%) accounting for the majority. People with severe mental illness and substance use disorders often have complex health needs including multiple comorbidities, more difficulties with daily living, and a higher likelihood of premature death. An estimated 8% (15.5 million) have both and a mental illness and a substance use disorder and combined, 33% (64.5 million) of nonelderly adults have a mild, moderate, or severe mental illness or substance use disorder (Figure 1).

Mental illness or substance use disorder is most common in young adults and nonelderly White people. Mental illness is most common in young adults aged 18 to 25 (30%) and lowest in adults 50 to 64 (17%). Among young adults aged 18 to 25, the rate of substance use disorders is 24%, twice as high as that of adults aged 50 to 64 (12%). More than one-quarter (26%) of White people experience mental illness; this is the highest rate of any race or ethnicity. White people are more likely to report substance use disorders (19%) compared to Hispanic people (14%) and Black people (16%). These findings for higher rates hold true for mild, moderate and severe mental illness and substance use disorder and for concurrent mental illness and substance use disorder (Figure 2). Other data and research point to worsening mental health for young adults and people of color during the pandemic. A lack of culturally sensitive screening tools that accurately detect mental illness, coupled with structural barriers, may lead to underdiagnosis of  mental illness among people of color.

Women have higher rates of mental illness, while men have higher rates of substance use disorder. Compared to men, women are more likely to experience mental illness (29% versus 17%). However, in contrast to mental illness, substance use disorders are more common in males than females (20% versus 15%) (Figure 2).

How are nonelderly adults with mental illness and substance use disorders covered and how does prevalence vary by coverage?  

Private insurance covers most nonelderly adults with mental illnesses and substance use disorders. Private insurance covers the majority of nonelderly adults with any mental illness (58%) and any substance use disorder (57%); combined, this represents over 37 million people with either condition covered by private insurance. Despite only covering 18% of the nonelderly adult population, Medicaid covers 23% of those with any mental illness and 21% of those with any substance use disorder, or an estimated 13.9 million people (Figure 3).

Mental illness and substance use disorders are most prevalent among nonelderly adults with Medicaid. As of 2020, an estimated 29% of Medicaid enrollees have a mental illness, relative to 21% of privately insured and 20% of uninsured people. About one in five (21%) Medicaid beneficiaries have a substance use disorder, similar to uninsured people (19%), but higher than privately insured people (16%). Further, Medicaid enrollees have the highest overall prevalence of moderate to severe mental illness or substance use disorders. Combined, 39% of Medicaid enrollees have a mental illness and/or substance use disorder, relative to 31% of privately covered and uninsured people. An estimated 11% of adults with Medicaid have both and a mental illness and a substance use disorder, relative to 7% of privately covered and 8% of uninsured people (Figure 4).

Among nonelderly adults with a moderate or severe mental illness or substance use disorder, Medicaid enrollees are more likely than those with private insurance to have chronic health conditions and to report fair or poor health. There is a high comorbidity between mental conditions and chronic physical conditions, which increases with severity of symptoms. The relationship is bidirectional, with physical conditions sometimes increasing the risk for mental conditions, and vice versa. Medicaid enrollees with moderate to severe mental illness or substance use disorders are more likely to report chronic conditions than those with private coverage, and a higher share reports two or more chronic conditions. Further, Medicaid enrollees with severe/moderate mental illness or substance use disorders report fair to poor health over twice as often as privately insured (36% and 13%, respectively) (Figure 5).