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

What does it mean if a condition is classified as a serious mental illness (SMI)?

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What Is a Serious Mental Illness (SMI)?

Serious mental illness, or SMI, is a term that public health authorities often use to categorize conditions that cause particularly disruptive symptoms.

The National Institute on Mental Health (NIMH) defines SMI as “a mental, behavioral, or emotional disorder resulting in serious functional impairment, which substantially interferes with or limits one or more major life activities.”

Somewhat surprisingly, there are no universally agreed-upon criteria to determine if a condition should be classified as an SMI. There are even discrepancies with the term itself, as some organizations call the category “severe mental illness” instead of serious mental illness.

This lack of consensus was highlighted in a systematic review that was published in July 2022 in the journal Psychiatric Services:

• The review involved an analysis of 788 papers that discussed either serious or severe mental illness
• Only 120 of the papers, or 15% of the total reviewed, included attempts to define SMI.
• Among those 120 papers, the review team found “substantial variation … regarding criteria applied and diagnoses included.”

“The term ‘SMI’ has poor reliability and validity across the empirical literature,” the authors concluded, “and its use should be consistently defined in future research or suspended in the absence of clear operational definitions.”

Are SMI Common?

SMI are a relatively small subset of all mental illnesses (AMIs). But in a nation as large as the United States, “relatively small” can still apply millions of people.

Here’s what the NIMH has reported about the prevalence of SMI among adults in the U.S., using data collected during the 2022 edition of the National Survey on Drug Use and Health (NS-DUH):

• About 59.3 million adults (or about 23.1% of the population ages 18 and above) had any mental illness in the past year.
• About 15.4 million adults (6% of the total population and 26% of those with AMI) had a serious mental illness in the previous 12 months.
• Women (7.1%) were more likely than men (4.8%) to be diagnosed with an SMI.

The NIMH also reported that about two-thirds of adults with SMI had received treatment in the past year. As with the diagnoses, women (71.4%) were more likely than men (59.3%) to have gotten professional help.

Examples of Serious Mental Illnesses

According to the NIMH definition of serious mental illness, any condition could qualify as an SMI if it significantly undermines a person’s ability to function. However, some disorders are more likely than others to have this type of effect.

Conditions that are frequently put into the SMI category include:

Schizophrenia

Schizophrenia is a highly disruptive mental illness with symptoms that include:

• Hallucinations – Seeing or hearing things that don’t actually exist
• Delusions – Rigidly clinging to beliefs that can be easily disproven or that have no basis in reality, such as claiming that you have magical powers or are being sent coded messages through mass media
• Disorganized speech – Being unable to think clearly and communicate your thoughts in a logical or understandable manner
• Grossly disorganized or catatonic behavior 
• Negative symptoms – Using minimal expressiveness or showing no interest in interacting with others

Schizoaffective disorder 

In addition to having at least two of the schizophrenia symptoms listed above, someone with schizoaffective disorder will also experience one or both of the following:

• Manic episodes – Periods of a least seven days during which they have symptoms such as increased energy, restlessness, inflated self-confidence, limited need for sleep, and racing thoughts. Manic episodes are also characterized by impulsivity in areas that can cause considerable harm, such as spending or gambling sprees, unwise business investments, reckless driving, unsafe sex, and substance abuse.
• Major depressive episodes – Periods of at least two consecutive weeks during which they have symptoms such as deep sadness, low motivation, decreased self-esteem, persistent fatigue, disrupted appetite and sleep patterns, and recurrent thoughts of death and dying.

Bipolar disorder

Depending on which type of bipolar disorder a person has, they may experience manic episodes, hypomanic episodes (which are similar to manic episodes but don’t last as long), and/or major depressive episodes. 

One version of bipolar disorder involves alterations between hypomania and major depression, with symptoms not lasting long enough at any one time to qualify as a full episode.

Some sources only include especially severe cases of bipolar disorder within the SMI category.

Major depressive disorder (MDD)

Major depressive disorder causes the same major depressive episodes that are described in the schizoaffective disorder section above. As with bipolar disorder, some sources only classify MDD as a serious mental illness if a person experiences extremely severe symptoms.

Posttraumatic stress disorder (PTSD)

PTSD, which can occur in the aftermath of one or several traumatic experiences, can cause symptoms such as:

• Dramatic mood swings
• Sense of being perpetually in danger
• Anxiety and paranoia
• Exaggerated startle response
• Difficulty concentrating and focusing
• Outbursts of anger, aggression, or violence
• Reckless or self-destructive behaviors
• Sense of detachment from other people
• Withdrawal and isolation
• Substance abuse

Obsessive-compulsive disorder (OCD)

People with OCD may have one or both of the following types of symptoms:

• Obsessions – Recurrent intrusive thoughts, which may include highly disturbing mental images, fear of becoming contaminated, or concern that they may harm or kill themselves or someone else.
• Compulsions – Repetitive behaviors that they feel forced to perform, such as showering multiple times per day, not leaving a room until they have turned a light on and off a specific number of times, or repeating certain words or numbers over and over again.

Obsessions and compulsions can be physical and emotionally exhausting, and may take up significant amounts of time on a daily basis.

Panic disorder

Panic disorder is a type of anxiety disorder that involves the sudden onset of intense fear along with symptoms such as:

• Dizziness
• Tingling in hands and feet
• Racing heart
• Chest pain
• Excessive perspiration
• Sense of detachment from your own mind and body
• Sense of unreality, as perceiving that the world has been suddenly drained of color or that you were viewing your surroundings through a pane of glass
• Sense of impending doom, which may include the belief that you are about to die

Treatment Options for SMI

Given the severity of their symptoms and the functional disruptions they cause, serious mental illnesses are often initially treated via inpatient or residential programming.

At these levels, patients live at the center where they are receiving care:

• Inpatient treatment is usually short-term, with the goal of helping a person achieve stabilization. 
• Residential programs often offer longer lengths of stay, so patients can begin to heal in a supportive environment where they are shielded from the stresses and pressures of daily life.

After completing inpatient and/or residential treatment, many people with SMI receive additional support in programs such as:

• Partial hospitalization program (PHP) – Full days of care, usually five days per week, but without a residential component
• Intensive outpatient program (IOP) – Partial days of care two to five days per week
• Outpatient treatment – Individual or group sessions schedule at the frequency that best meets their needs
• Virtual treatment – Attending individual or group therapy sessions via a secure online videoconferencing platform

Learn More About Treatment for Serious Mental Illnesses in Tennessee

Time Wellness Tennessee offers a full continuum of customized programming for individuals with SMI, other mental health concerns, and co-occurring addictions.

Treatment options at our center in Chattanooga, TN, include a residential program, a PHP, an IOP, outpatient therapy, and virtual care.

To learn more about how we can help you or a loved one, or to schedule a free assessment, please visit our Admissions page or call us today.