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What is a Serious Mental Illness?

Feb 4, 2021

You may have heard the term “serious mental illness” before. But what is a serious mental illness? How is it different from other types of mental illness? What makes it serious? In this article, we break down what a serious mental illness is and what it means.

A mental illness is a disorder that affects your mood, feelings, behavior, or thinking. A serious mental illness, also abbreviated “SMI”, is defined as a “diagnosable mental, behavior, or emotional disorder that causes serious functional impairment that substantially interferes with or limits one or more major life activities.”

To be categorized as a “serious mental illness”, a disorder has to severely disrupt your normal functioning. It may cause you to be unable to work, make friends, or stay connected to reality. 

Warning Signs of a Serious Mental Illness

Serious mental illnesses are typically diagnoses of schizophrenia, bipolar disorder, or major depressive disorder. 

Schizophrenia is a disorder that causes individuals to feel out of touch with reality, and can severely affect their daily functioning. 

Common symptoms of schizophrenia:

  • Experiencing hallucinations or delusions
  • Having disorganized thinking, speech, or behavior
  • Other symptoms that inhibit the ability to function normally

Bipolar disorder causes an individual to have extreme mood swings that affect many aspects of their lives. Individuals with bipolar disorder experience manic episodes and depressive episodes. 

Symptoms of manic episodes include:

  • Feeling abnormally upbeat or jumpy
  • Feeling agitated
  • Having an abnormal amount of energy
  • Impaired judgment
  • Behaving unpredictably
  • Sleeping less
  • Racing thoughts
  • Being easily distracted

Symptoms of depressive episodes include:

  • Severely depressed mood
  • Loss of interest in most activities
  • Changes in eating or weight gain
  • Sleeping too little or too much
  • Fatigue or loss of energy
  • Feeling guilty
  • Thoughts of suicide

Major depressive disorder, also known as depression, is a disorder that causes persistent negative effects on your mood. Depression can range in severity and can make daily functioning a challenge. Depression can count as a serious mental illness when it is especially severe.

Here are common symptoms of severe depression:

  • Feelings of sadness, hopelessness, or emptiness
  • Sleeping too little or too much
  • Loss of interest in most activities
  • Fatigue or loss of energy
  • Persistent feelings of doom
  • Thoughts of suicide or suicide attempts
  • Loss of ability to take care of one’s needs and hygiene 

If you or a loved one is experiencing symptoms of any of these disorders, reach out to your doctor or mental health professional. If you or a loved one is experiencing suicidal thoughts or behaviors, call 911 or contact the National Suicide Prevention Lifeline at 1-800-273-8255.

Causes of Serious Mental Illnesses

Mental illness is never your fault. Many different factors can be at play.

Genetics. Mental illnesses can run in families. If you have a relative who has a disorder, you may be more likely to have it as well.

Environmental factors. Things like stress, substance abuse, trauma, and significant life changes can make you more vulnerable to developing a serious mental illness.

Brain differences. Brain structure and chemistry may play a role in developing a serious mental illness.

Treatment for Serious Mental Illnesses

Serious mental illnesses like schizophrenia, bipolar disorder, and severe depression are treatable. You may find a combination of treatment, such as medication and therapy, is helpful in your recovery. 

Medications. The goal of medication is to make your symptoms more manageable. Different medications work for different disorders and different people. Talk to your doctor or mental health professional about taking medications. 

Psychotherapy. Psychotherapy is also known as talk therapy and involves working with a mental health professional to identify and change harmful thoughts and behaviors. It can be helpful for learning to manage your disorder. It can also help you make changes to avoid exacerbating your symptoms in the future.

Lifestyle changes. Your mental health professional may suggest implementing additional healthy habits into your life, like eating right, getting exercise, meditating, or joining a support group.

Inpatient mental health treatment. When your symptoms make it difficult to function, you may need to go to the hospital or a mental health crisis center. This type of treatment can help you stabilize your symptoms and develop a plan to move forward. If you are currently in need of crisis mental health services in the Twin Cities metro, call Guild’s crisis services in St. Paul at (612) 267-5242 or in Savage at (651) 347-9889. If you are located outside of Minnesota, call 911 to get connected to crisis centers. 

We Know Serious Mental Illness

At Guild, we work with individuals with serious mental illnesses daily. We use expert and person-centered approaches in our services to help individuals with their recovery.

Interested in our services? Learn more here.

Want to make a donation to help us continue to serve people with serious mental illness? Donate here.



Mental Health and Substance Abuse Disorders, Substance Abuse and Mental Health Services Administration. 

Mental Illness, National Institute of Mental Health. 

Key Substance Abuse and Mental Health Indicators in the United States, Substance Abuse and Mental Health Services Administration.

Adults With SMI and Children/Youth With SED, Substance Abuse and Mental Health Services Administration. 

Mental Health By the Numbers, National Alliance on Mental Illness. 

Schizophrenia, Mayo Clinic. 

Bipolar Disorder, Mayo Clinic. 

Bipolar Disorder, National Alliance on Mental Illness. 

Warning Signs of Severe Depression, Web MD. 

Depression, National Alliance on Mental Illness.

Psychotherapy, National Alliance on Mental Illness.