What is serious mental illness in adults and what is not?

Serious mental illnesses are a small subset of the 300 mental illnesses that are in DSM. While it is fair to debate where the line between serious mental illness (SMI) and poor mental health is, the extremities are clear. The Center for Mental Health Services defined SMI as

mental illnesses listed in DSM that “resulted in functional impairment which substantially interferes with or limits one or more major life activities.” (CMHS 1999)

 By all accounts, serious mental illnesses include “schizophrenia-spectrum disorders,” “severe bipolar disorder,” and “severe major depression” as specifically and narrowly defined in DSM. People with those disorders comprise the bulk of those with serious mental illness. However, when other mental illnesses cause significant functional impairment they also count as a serious mental illness.  

According to the National Institute of Mental Health, serious mental illness is relatively rare, affecting only 5% of the population over 18. Serious mental illness includes schizophrenia; the subset of major depression called “severe, major depression”; the subset of bipolar disorder classified as “severe” and a few other disorders.

Schizophrenia (NIMH defines all schizophrenia as “severe”):  1.1% of the population (FN 1)
The subset of bipolar disorder classified as “severe”:  2.2% of the population (FN 2)
The subset of major depression called “severe, major depression”:  2.0% of the population (FN 3)

Therefore total “severe” mental illness in adults by diagnosis: 5.3% of the population (FN 4)

US mental health spending and mental health non-profits focus almost exclusively on people who do not have serious mental illness, rather than those who do. This is the single major problem with the US mental health system. Money is not lacking. Prioritization is.
We should replace mission creep with mission control and return the mental health system to one that gets treatment to those with the most serious mental illness rather than one that works to improve the mental health of all others.

 Following are the footnotes 

 (1) NIMH classifies all Schizophrenia as severe. “Schizophrenia is a chronic, severe, and disabling mental disorder characterized by deficits in thought processes, perceptions, and emotional responsiveness. http://www.nimh.nih.gov/statistics/1SCHIZ.shtml 

(2) NIMH “Bipolar Disorder Among Adults” “2.2% of U.S. adult population are classified as “severe”. http://www.nimh.nih.gov/statistics/1BIPOLAR_ADULT.shtml. See note below under “major depressive disorder” to see how severity was defined.

 (3) Major Depressive Disorder Among Adults” http://www.nimh.nih.gov/statistics/1MDD_ADULT.shtm NIMH notes that 6.7% of adults have major depression and 30.4% of those (2.0% of U.S. Population) is classified as “severe”, quoting Kessler RC, Chiu WT, Demler O, Walters EE. Prevalence, severity, and comorbidity of twelve-month DSM-IV disorders in the National Comorbidity Survey Replication (NCS-R). Archives of General Psychiatry, 2005 Jun;62(6):617-27. To be classified as ‘severe’ in addition to meeting DSM criteria, the disorder had to meet the following criteria. “Twelve-month cases were classified as serious if they had any of the following: a 12-month suicide attempt with serious lethality intent; work disability or substantial limitation due to a mental or substance disorder; positive screen results for non- affective psychosis; bipolar I or II disorder; substance depen- dence with serious role impairment (as defined by disorder- specific impairment questions); an impulse control disorder with repeated serious violence; or any disorder that resulted in 30 or more days out of role in the year.” The study is available at http://apsychoserver.psych.arizona.edu/JJBAReprints/PSYC621/Kessler%20et%20al%20Arch%20Gen%20Psych%202005b.pdf

(4) “Prevalence of Serious Mental Illness Among U.S. Adults by Age, Sex, and Race in 2008 (NSDUH)” at http://www.nimh.nih.gov/statistics/SMI_AASR.shtml