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What is Serious Mental Illness?

Serious Mental Illness (SMI) is defined as someone over the age of 18 who has (or had within the past year) a diagnosable mental, behavioral, or emotional disorder that causes serious functional impairment that substantially interferes with or limits one or more major life activities.

SMI is a small subset of the 300 mental illnesses listed in The Diagnostic and Statistical Manual of Mental Disorders (DSM). SMI includes disorders such as bipolar disorder, major depressive disorder, schizophrenia, and schizoaffective disorder.

All mental health conditions have the potential to produce impairment 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 can vary, too. It may depend on whether the term is used for legal, clinical, or epidemiological purposes.

How Did the Definition of Serious Mental Illness Evolve?

The line between serious mental illness (SMI) and other mental health concerns can at times be confusing. Several national efforts to define SMI came to similar conclusions and arrived at similar estimates of the number of people that SMI affects.

In the early 1990s, the Center for Mental Health Services (CMHS) had to define serious mental illness when it was created.They had to do this in order to distribute mental health block grants that were proportional to the number of cases of SMI in each state. They defined SMI as mental illnesses listed in the DSM that “resulted in functional impairment which substantially interferes with or limits one or more major life activities.” To calculate how many adults in each state had SMI, CMHS had to define “functional impairment.” After doing that, CMHS noted that “90% [of those meeting the criteria for serious mental illness] either have a severe disorder like schizophrenia or bipolar disorder, or a disorder and work impairment, or a disorder and report being suicidal.”

In 2008 data, the National Institute of Mental Health (NIMH) concluded that serious mental illness (SMI) affects 4.4% of the population over 18.2 It defined SMI to include:

Other Efforts to Define Serious Mental Illness

Another effort to define serious mental illness and calculate the number of people it affects took place in 1993. The Senate Appropriations Committee asked the National Advisory Mental Health Council to report on how much it would cost to provide insurance coverage for people with “severe mental illness” commensurate with the coverage of other illnesses.3 It stipulated that “severe mental illness” is defined through diagnosis, disability, and duration, and includes disorders with psychotic symptoms such as schizophrenia, schizoaffective disorder, manic depressive disorder, autism, as well as severe forms of other disorders such as major depression, panic disorder, and obsessive compulsive disorder. Using that definition, they concluded that 3% of adults have severe mental illness. This estimate is close to what CMHS and NIMH found.

The federal definition of serious mental illness is the result of a mandate from the 1992 Alcohol, Drug Abuse, and Mental Health Administration Reorganization Act.4 This definition was created by the U.S. Department of Health and Human Services (HHS). It was meant to help states – that were applying for grant funds to support mental health services – estimate the incidence and prevalence of SMI. Federal use of the term “chronic mental illness” ended after consumers and advocates argued that the term had negative connotations. They felt it suggested that some forms of mental illness are intractable. As a result, chronic mental illness was changed to severe and persistent mental illness, and later to serious mental illness.

What is Considered a Serious Mental Illness?

Serious mental illness (SMI) includes:

Some terms related to SMI are used interchangeably:

  • Affective disorders ≈ mood disorders
  • Bipolar disorders ≈ manic–depressive disorder/manic depression
  • Major depressive disorders ≈ major depression

It is helpful to be aware of other terms that are often used as part of broader categories of mental health conditions. These often come up around SMI:

  • Mood disorders – depressive disorders, bipolar disorders
  • Anxiety disorders – posttraumatic stress disorder, for example
  • Psychotic disorders – schizophrenia, delusional disorder, schizoaffective disorder

The National Alliance on Mental Illness (NAMI) uses the terms “mental health conditions” and “mental illness/es” interchangeably.5 NAMI notes that:

A mental health condition isn’t the result of one event. Research suggests multiple, linking causes. Genetics, environment and lifestyle influence whether someone develops a mental health condition. A stressful job or home life makes some people more susceptible, as do traumatic life events. Biochemical processes and circuits and basic brain structure may play a role, too.

How many adults in the US experience a Serious Mental Illness?

The 2019 National Survey on Drug Use and Health provides data on how many adults experience serious mental illness (SMI) in the United States.6 It is prepared by the Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration, U.S. Department of Health and Human Services. The study sheds light on prevalence across age groups, as well as various demographic and socioeconomic factors around SMI.

In 2019, an estimated 13.1 million adults had SMI in the past year, which corresponds to 5.2 percent of adults. Here is a breakdown of SMI in specific age groups:

  • Age 18 to 25 = 2.9 million (8.6 percent of people in this age group)
  • Age 26 to 49 = 6.8 million (6.8 percent)
  • Age 50 or older = 3.4 million (2.9 percent)

The same 2019 national survey provides other important data around individuals who have SMI.

  • 16.9 percent of individuals who have SMI have incomes below the poverty level
  • 46.2 percent of people who have SMI have full-time employment
  • 65.5 percent (8.6 million) of adults with SMI received treatment in the past year; 34.5 percent received no treatment
  • 71.6 percent of individuals with SMI have some form of insurance (private, Medicare, other)
  • Approximately 3.6 million adults had co-occurring SMI and a substance use disorder (SUD) in the past year, which corresponds to 1.4 percent of adults
  • The percentages of adults who used illicit drugs in the past year were higher among those with SMI (49.4 percent, 6.5 million) compared with those without any mental illness (16.6 percent, 32.9 million)
  • About 6.2 million (47.7 percent) adults aged 18 or older with SMI perceived an unmet need for mental health care in the past year

What treatments are effective for Serious Mental Illness?

Treatment choices for serious mental illness (SMI) 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 enhance the experience of treatment and improve outcomes.

There are many tools and treatments that may be part of a well-rounded 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, it 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 or touching the brain directly 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).

How can caregivers help individuals who have Serious Mental Illness?

Family members and caregivers often play a large role in helping and supporting a loved one who has serious mental illness (SMI). A 2016 study by the National Alliance for Caregiving, in partnership with Mental Health America and the National Alliance on Mental Illness, estimated that more than 8 million Americans provide care to an adult with an emotional or mental health issue, mainly related to SMI.7

The term caregiver may also extend beyond an individual’s family. This includes friends, teachers, neighbors, coworkers and others in the community. Hence, the term caregiver can refer to anyone who gives emotional, financial, or practical support to a person with SMI.

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 may:

  • Ask questions, listen to answers, and learn about a loved one’s concerns.
  • Contact health care professionals to make and coordinate appointments.
  • Educate family members, friends, and colleagues of their loved one 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.
  • Help prepare a crisis plan that makes their loved one’s treatment preferences known.
  • Notice any symptoms, especially those that may indicate a loved one is experiencing a crisis.
  • 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.
  • Use person-first language to discuss and describe mental health conditions.

The 2016 study also highlights some of the challenges that caregivers may face. Four in 10 caregivers struggled to find an accurate diagnosis for their loved one. Families reported that it took 11.8 years, on average, for their loved one to receive an accurate diagnosis. Caregivers noted several barriers to accessing health care services and long-term services and supports. This includes day programs, peer support, case managers, inpatient treatment centers, and low availability of services in rural areas.

At times, caregivers can suffer from physical and/or emotional stress. They often put others’ needs before their own. When taking care of a loved one, caregivers invest a great deal of time and energy. In turn, they may overlook their own physical and emotional needs. This can lead to stress, anxiety, and/or depression.  Many clinics provide family psychoeducation, family support groups, and other services to assist caregivers.

Do you have questions about Serious Mental Illness?

If you are an individual or family member and want more information about serious mental illness (SMI), you can find many resources in our section for individuals and families. You can also use the SMI Adviser Knowledge Base to browse hundreds of evidence-based answers and resources.

If you are a mental health clinician and have a question about evidence-based treatments, research, or where to find resources for individuals, submit a question and get a free consultation from SMI Adviser’s national experts.

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