Serious mental illness (SMI) is generally defined as a condition in which an individual over the age of 18 has a diagnosable mental, behavioral, or emotional disorder that causes serious functional impairment, substantially interfering with or limiting one or more major life activities.

All mental health conditions have the potential to cause problems with functioning and interfere with quality of life. Thus, many instances of mental illness may broadly qualify as “serious” according to various uses and interpretations of the term. Definitions of serious mental illness may vary, depending on whether the term is used for legal, clinical, or health research purposes.

SMI includes a small subset of the more than 300 mental illnesses listed in the latest edition of the Diagnostic and Statistical Manual of Mental Disorders^® (DSM-5-TR^® (Fifth Edition, Text Revision), published in 2022). SMI includes:

• Schizophrenia spectrum disorders
• A subset of major depression called “severe, major depression”
• A subset of bipolar disorder classified as “severe”
• A few other disorders

In 2024, an estimated 14.6 million adults (aged 18 and over) had SMI in the past year, or about 5.6% percent of adults (1 - Figure 52 and Table A.38B). The percentage varies by specific age groups:

• Age 18–25: 9.4%
• Age 26–49: 7.5%
• Age 50+: 2.8%

National survey data from 2024 provides additional insights into the population with SMI. Among adults with SMI:

• 24% have incomes below the federal poverty level (1 - Table 6.8A)
• 43% are employed full-time (1 - Table 6.7A)
• 29% received treatment in the past year (1 - Table 6.21A)
• 43% perceived an unmet need for mental health care (they sought treatment or thought they should get treatment and did not receive treatment) (1 - Table 6.32A)

Treatment choices for serious mental illness and any mental health conditions vary from person to person. Even people with the same diagnosis have different experiences, needs, goals and objectives for treatment. There is no “one size fits all” treatment.

Choosing the right mix of treatments and supports is an important step in the recovery process. When individuals are actively involved in designing their own treatment plan, including defining recovery and wellness goals, it can improve their experience and outcomes.

There are many tools and treatments that may be part of a recovery plan for SMI.

• Psychotherapy explores thoughts, feelings, and behaviors, and seeks to improve an individual’s well-being. Examples include cognitive behavioral therapy, interpersonal psychotherapy, and family psychoeducation.
• Medication does not cure mental illness. However, medication may reduce the frequency or severity of symptoms, which can allow for improved quality of life and recovery.
• Interventions such as Assertive Community Treatment, supportive employment, and supportive housing are evidence-based treatments that can support a recovery plan.
• Complementary and alternative medicine (CAM) refers to treatment and practices that are not typically associated with standard care. CAM may be used in place of or in addition to standard health practices. Examples include yoga, meditation, tai chi, relaxation exercises, and other mind-body medicine techniques.
• Brain stimulation therapies involve stimulating the brain with electricity, magnets, or implants. These options are often considered when medication and therapy are not able to relieve the symptoms of mental health conditions. Examples are electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS). (See more on brain stimulation therapies.)

Family members and caregivers often play a large role in helping and supporting a loved one who has serious mental illness. An estimated 59 million U.S. adults are family caregivers, and 27% (or about 16 million adults) report caring for a family member because of an emotional or mental health issue, according to a 2025 report from AARP & National Alliance for Caregiving (2).

Caregivers can help loved ones who have SMI in many ways. Yet it is often a learning process, as every person with a mental health condition experiences it in a slightly different way. Caregivers can:

• Ask questions, listen to answers, and learn about a loved one’s concerns.
• Educate family members, friends, and colleagues of their loved ones about the condition(s) they are experiencing.
• Encourage loved ones to follow their treatment plans and offer reminders about therapy sessions, appointments, medications, and more.
• Notice any symptoms, especially those that may indicate a loved one is experiencing a crisis.
• Use person-first language to discuss and describe mental health conditions.

Working together with their loved ones, caregivers may:

• Contact health care professionals to make and coordinate appointments.
• Help prepare a crisis plan that makes their loved one’s treatment preferences known.
• Organize information on mental and physical health records, treatment providers, medications and treatments, crisis plans, and more.
• Take loved ones to their appointments.
• Participate in treatment with their loved ones.

Read more on Helping a Loved One Cope with Mental Illness (from APA) and more on Support for Caregivers (from the APA Foundation, Mental Healthcare Works Campaign).

Physician Review

Vedrana Hodzic, M.D.
Director of Fellowships and Medical Education
American Psychiatric Association Foundation

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