Understanding Serious Mental Illness (SMI) and How To Treat It

Articles about the prevalence and impact of mental health disorders sometimes organize these conditions into two categories: any mental illness (AMI) and serious mental illness (SMI). What is an SMI and how are conditions in this category treated?

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What Is a Serious Mental Illness (SMI)?

Here’s how the National Institute on Mental Health (NIMH) defines any mental illness (AMI) and serious mental illness (SMI):

• AMI: A mental, behavioral, or emotional disorder with an impact that can range from no impairment at all to mild, moderate, or severe impairment.
• SMI: A mental, behavioral, or emotional disorder that causes “serious functional impairment,” meaning that it either interferes with or limits a person’s ability to engage in one or more major life activities.

AMI is the larger category, encompassing every mental illness, regardless of its impact. SMI is a subset of AMI, referring only to conditions that cause significant disruptions in a person’s life.

One other important facet of the SMI designation is that it sometimes only refers to individuals within a certain age range:

• Some sources, such as the authors of a December 2021 editorial in the journal Frontiers in Psychiatry, use the term SMI when referring to patients of all ages. 
• Others, such as the Substance Abuse and Mental Health Services Administration (SAMHSA), reserve the SMI category solely for adults ages 18 and above. 
• SAMHSA uses the term serious emotional disturbance (SED) to classify serious mental illnesses among children and adolescents. 

Examples of SMIs

Technically, any mental health disorder can be an SMI if it has a serious negative impact on a person’s ability to function. However, certain conditions are much more likely than others to have this type of impact.

Disorders that are frequently described as SMIs include:

• Bipolar I disorder 
• Bipolar II disorder
• Major depressive disorder (MDD)
• Schizophrenia
• Schizoaffective disorder 
• Schizophreniform disorder
• Borderline personality disorder (BPD)
• Obsessive-compulsive disorder (OCD)
• Post-traumatic stress disorder (PTSD)

Prevalence of Serious Mental Illnesses

Though SMI is a much smaller category than AMI, serious mental illnesses still affect millions of people.

According to the 2024 edition of the National Survey on Drug Use and Health (NS-DUH):

• About 61.5 million adults, or about 23.4% of the population ages 18 and above, had any mental illness (AMI) in the previous year. 
• The rate of AMI was highest among adults in the 18-25 category, with 11.6 million people, or 33.2% of that demographic, group affected.
• About 14.6 million adults met the criteria for a past-year serious mental illness (SMI). This represents about 5.6% of the entire adult population and about 23.7% of adults with any mental illness.
• The rate of past-year SMI was also highest (9.4%) within the 18-25 category.
• Among adults with an SMI, 6.9 million, or about 47.2%, also had a co-occurring substance use disorder (addiction).

Effects of Serious Mental Illnesses

As indicated by the final bullet point in the previous section, one effect of serious mental illness is an increased risk of addiction. 

Data collected during the 2024 NS-DUH indicates that about 17.7% of all adults in the U.S. had a substance use disorder in the past 12 months. This means that the rate of addiction among adults with an SMI is more than 2.5 times higher than among the general public.

In addition to addiction, other negative outcomes that have been linked with SMIs include:

• Onset or worsening of other mental health conditions
• Delayed or diminished academic progress
• Difficulty finding and keeping a job
• Financial problems
• Medical concerns due to problematic behaviors and poor self-care
• Inability to maintain an independent lifestyle
• Increased risk of being victimized
• Decreased quality of life
• Lower life expectancy

In September 2021, the journal Psychological Medicine published a survey of life expectancy among residents of South East London. This survey found that the life expectancy of adults with SMIs was more than 14 years shorter than among the general public in that area.  

What Causes SMIs?

There’s no single, definitive cause of any SMI. Instead, experts have identified a range of factors that can increase a person’s risk of developing a serious mental illness. These factors include:

• Family history of mental illness
• Prior struggles with other mental health concerns
• Adverse childhood experiences (ACEs) such as physical abuse, sexual assault, and neglect
• Traumatic experiences during adolescence or adulthood
• Serious and/or chronic medical conditions
• Certain genetic variations
• Abnormal brain chemical levels
• Problematic pregnancy or childbirth
• Advanced paternal age at time of birth
• Exposure to certain infectious agents
• Early use of alcohol or other addictive drugs

Treatment Options for Serious Mental Illnesses

Treatment for someone with an SMI can be influenced by a range of factors such as:

• Their age, gender, and developmental level
• Their treatment history
• Which disorder or disorders they have
• The type and severity of their symptoms
• How these symptoms have affected their ability to function
• If they have any co-occurring medical concerns
• If they gave been abusing or become addicted to alcohol or another substance
• The effectiveness of their personal support network

Given the degree of disruption that SMIs can cause, many people with these conditions begin treatment in an inpatient or residential environment, then step down to one or more of the following levels for additional support:

• Partial hospitalization program (PHP)
• Intensive outpatient program (IOP)
• Outpatient therapy or counseling

Depending on the severity of the patient’s needs and the parameters of the program they’re in, mental health treatment for SMIs often involves both medication and therapy. Prescription medications that may be beneficial for people with serious mental illnesses include:

• First- or second-generation antipsychotics
• Selective serotonin reuptake inhibitors (SSRIs)
• Serotonin-norepinephrine reuptake inhibitors (SNRIs)
• Norepinephrine-dopamine reuptake inhibitors (NDRIs)
• Mood stabilizers
• Benzodiazepines
• Stimulants
• Beta-blockers

The therapeutic part of treatment for someone with a serious mental illness may include elements such as:

• Individual, group, and family therapy sessions
• Cognitive behavioral therapy (CBT)
• Dialectical behavior therapy (DBT)
• Eye movement desensitization and reprocessing (EMDR) therapy
• Biofeedback
• Red light therapy
• Holistic therapies such as meditation and mindfulness
• Experiential therapies such as art and music
• Life skills education

Find Mental Health Treatment in Atlanta

Time Wellness Georgia offers customized outpatient care for adults and adolescents who have SMIs, other mental health concerns, and co-occurring addictions.

Treatment options at our center in Atlanta, GA, include a PHP, an IOP, an evening IOP for adolescents, and virtual care. In each program, your loved one can expect to receive customized services and comprehensive support from a team of skilled professionals who are truly invested in their success.

For answers to any questions about our programs and services, or to schedule a free assessment, please visit our Contact page or call us today.