About 50% of individuals with severe psychiatric disorders (3.5 million people) are receiving no treatment.

SUMMARY: For the past 20 years, studies have consistently estimated that almost half of all individuals with schizophrenia or bipolar disorder are receiving no treatment for their mental illness at any given time. According to recent estimates of NIMH, this means that approximately 3.5 million such individuals are receiving no treatment.

* * *45 percent untreated

In 2010, the National Institute of Mental Health (NIMH) estimated that 40 percent of adults with schizophrenia and 51 percent of individuals with severe bipolar disorder receive no treatment in a one-year period. NIMH also estimated that there are 2.6 million adults with schizophrenia (1.1% of the adult population) and 5.1 million adults with severe bipolar disorder (2.2% of adult population). That means that there are 3.5 million adults with schizophrenia or bipolar disorder not being treated in the US on any given day.
NIMH website. Prevalence of serious mental illness among U.S. adults by age, sex, and race. http://www.nimh.nih.gov/statistics/SMI_AASR.shtml; http://www.nimh.nih.gov/statistics/1SCHIZ.shtml; http://www.nimh.nih.gov/statistics/1BIPOLAR_ADULT.shtml; http://www.nimh.nih.gov/statistics/1MDD_ADULT.shtml; all accessed March 22, 2011.

41 percent untreated

Mark Olfson et al. at Columbia reanalyzed 2003 national Medicaid claims for 49,239 individuals with schizophrenia who were hospitalized. They found that 41 percent of the patients received no psychiatric follow-up treatment in the month following their discharge from the hospital. The strongest predictors of which patients would not get follow-up treatment were substance abuse and a history of not having received treatment prior to their hospitalization.
Olfson M, Marcus SC, Doshi JA. Continuity of care after inpatient discharge of patients with schizophrenia in the Medicaid program: a retrospective longitudinal cohort analysis. Journal of Clinical Psychiatry 2010;71:831–838.

54 percent untreated

Using data for the National Comorbidity Survey (NCS) carried out in 1990–1992, the authors reported that 54 percent of individuals with serious mental illness (broadly defined) had received no treatment in the previous 12 months.
Kessler RC, Berglund PA, Bruce ML et al. The prevalence and correlates of untreated serious mental illness. Health Services Research 2001;36:987–1007.

46 percent untreated

By examining prescription refill records on 25,000 patients, it was found that 46 percent of individuals who had been taking antipsychotic medications were no longer taking the medications 9 months later. This study focused only on patients who were in the treatment system and did not include those who were homeless, incarcerated, etc.
Vanelli M, Burstein P, Cramer J. Refill patterns of atypical and conventional antipsychotic medications at a national retail pharmacy chain. Psychiatric Services 2001;52:1248–1250.

42 percent untreated

In another follow-up of the ECA study data, it was established that 42 percent of individuals with severe mental illnesses (as defined by the NIMH Advisory Mental Health Council) were not being treated.
Narrow WE. Mental health service use by Americans with severe mental illnesses. Social Psychiatric Epidemiology 2000;35:147–155.

35 percent untreated

In the five-site Epidemiologic Catchment Area (ECA) survey carried out 1980–1985, it was reported that 35 percent of individuals with schizophrenia and 35 percent of individuals with bipolar disorder had received no treatment in the previous 12 months.
Health care reform for Americans with severe mental illnesses: report of the National Advisory Mental Health Council. American Journal of Psychiatry 1993;150:1447–1465.