I talk about serious mental illness a lot, but I have failed to answer the specific question, what is a serious mental illness. Today I’m going to do that. I’m also going to talk about why it’s important to separate those with a serious mental illness and not just lump everyone with a mental illness together. As a person with bipolar disorder, a serious mental illness, I do feel strongly about this.

What Is a Mental Illness? Who Has a Mental Illness?

One of the things that bugs me intensely is when people say, “One in five Americans live with a mental illness.”

There tends to be no further information when people say it. People seem to think that by saying 20 percent of people live with a mental illness, that will destigmatize mental illness or help those people in some way. I can’t count the number of times I’ve seen that statistic with no context whatsoever.

But context matters. When people say that one in five Americans live with a mental illness, it isn’t wrong, per se, but it includes every mental illness under the sun. It includes everything from mild anxiety to bipolar disorder. It includes all recognized mental illnesses, from mild to severe. It includes all those people living normal, happy lives with just a small, nagging mental illness affecting five percent of their consciousness, to people who are so disabled they cannot live on their own because a mental illness has completely co-opted their brain. I don’t think lumping all those people together is useful or responsible. And I really don’t think that mental health/illness organizations are doing anyone a favor by shouting that statistic over and over without any context.

What Is a Serious Mental Illness?

According to the National Institute of Mental Health (NIMH), serious mental illness is defined as:

“a mental, behavioral, or emotional disorder resulting in serious functional impairment, which substantially interferes with or limits one or more major life activities. The burden of mental illnesses is particularly concentrated among those who experience disability due to SMI [serious mental illness].”

Because they are the National Institute of Mental Health, that definition is dry, has no teeth and is almost bereft of meaning. But believe me, the meaning is substantial. What it means is that people with a serious mental illness are the ones suffering. People with serious mental illnesses are the ones who are disabled. People with serious mental illness are the ones that can’t work. People with serious mental illness are the ones on the street. People with serious mental illness are the ones that go from jail to the psych ward and back again, over and over. For many people with serious mental illness, their pain is interminable.

This is distinctly different from someone who needs therapy to deal with a minor mental illness but otherwise works, lives, learns and loves just like everyone else.

Who Has a Serious Mental Illness?

It’s unclear exactly which mental illnesses the National Institute of Mental Health considers to be “serious” mental illnesses. In my estimation (and in the estimation of Mental Illness Policy Org), serious mental illnesses are:

  • Almost all cases of schizophrenia
  • Most cases of bipolar disorder
  • Some cases of major depression

In other words, it’s not so much the mental illness that makes it “serious,” it’s the severity.

When you look at the three above categories, the following are the numbers:

  • Schizophrenia (NIMH defines all schizophrenia as “severe”): 1.1 percent of the population
  • The subset of bipolar disorder classified as “severe”: 2.2 percent of the population
  • The subset of major depression called “severe major depression”: 2 percent of the population

Therefore total “severe” mental illness in adults by diagnosis: 5.3 percent of the population without accounting for overlap (remember, some people can have schizophrenia and major depression; this actually isn’t uncommon). The Substance Abuse and Mental Health Services Administration (SAMHSA) puts the overall rate at 4 percent.

So, using my definition where severity indicates the seriousness of mental illness, it’s only about 4-5 percent of people that have a serious mental illness.

Why Do Serious Mental Illness Matter?

Thus, it’s the tremendous minority of people with mental illness that actually have a serious mental illness. The thing is, it’s that minority that is drastically impaired and thus it is that minority that needs to be recognized and help with further services. About 65 percent of people with serious mental illness have received treatment in the last year. Considering how impaired and disabled these people are that number should be 100 percent. We should be focusing our efforts and our money, not on “awareness campaigns” or “anti-stigma campaigns” that help those without serious mental illness, but, rather, on outreach and treatment of those with serious mental illness. See, people are always going to feel comfortable with people just like them who happen to feel a bit of anxiety or depression, but people are not comfortable with the woman screaming, barefoot, on the corner — but that woman is the one in need of help. That woman represents where funding should go. But it’s that woman who would have the hardest time getting help.

The reason we need to separate those with serious mental illness from those with any mental illness is because we need to recognize the needs of these people. We need not to normalize serious mental illness, but, rather, recognize that it is not normal and therefore needs abnormal amounts of help. Saying this is not negative. Saying this is acknowledging reality.

So, feel free to use the one-in-five statistic if you like, but add that only about 4-5 percent of people have a debilitating, disabling mental illness. Focus on them so that the healthcare system, funding and other groups are forced to recognize and help these people who need it the most.


  1. National Institute of Mental Health, Mental Illness. Updated January 2021.
  2. Jaffe, D., “What Is Serious Mental Illness and What Is Not?” Mental Illness Policy Org, Sep. 2017.

Image by: Jiri Hodan, CC0, via Wikimedia Commons.