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Severe mental illness (SMI) is defined as “a mental, behavior, or emotional disorder” diagnosable according to the Diagnostic and Statistical Manual (DSM) that results in significant functional impairment.2,3 A traditional focus for public mental health systems has been to treat SMI, which account for a disproportionate amount of disability among all mental disorders.1 However, public health approaches to treat mental illness have gradually shifted toward progressively earlier identification and treatment strategies, including preventive strategies. Most of these efforts have been on SMIs such as bipolar disorder and psychotic disorders (including schizophrenia); accordingly, this review focuses on these disorders.


Because many SMI are chronic in nature, these disorders constitute some of the most debilitating illnesses globally.1 Mental illness and substance use disorders accounted for 7.4% of worldwide Disability Adjusted Life Years (DALYs) in 2010, a measure of disease burden.1 Of the proportion of DALY’s accounted for by mental and substance use disorders globally, schizophrenia accounted for 7.4% and bipolar disorder accounted for 7.0%.1 SMI thus severely and adversely impacts an individual’s functioning and life chances.2

Bipolar disorder and schizophrenia are considered major types of SMI due to their resulting impairment.3 In addition to other criteria, those diagnosed with bipolar disorder experience the occurrence of a manic episode in which a person experiences elevated mood and energy levels lasting most of the day for most days out of at least 1 week.5 Worldwide, lifetime prevalence of bipolar I disorder was found to be approximately 0.6%.6 In the United States, data from the National Comorbidity Survey Replication estimated lifetime prevalence of bipolar I to be 1%.7

A diagnosis of schizophrenia is characterized by the occurrence of two or more of the following symptoms occurring during a time period of 1 month and for a significant amount of time: delusions, hallucinations, disorganized speech, disorganized or catatonic behavior, or negative symptoms.5Additionally, one or more of the symptoms experienced must include delusions, hallucinations, or disorganized speech.5 These symptoms must persist over a 6-month period, although only 1 month of active symptoms is required, and are not explainable by other factors (e.g., organic cause or substance abuse).5 To be diagnosed, significant disturbances in functioning (i.e., at work, relationships, etc.) must be present.5 While variation in prevalence exists, the average point prevalence for schizophrenia is estimated to be 4.6 per 1000 people.8 Several large-scale studies have found 12-month prevalence estimates to range from 0.5% to 1.1% in the United States.9–11 Key to early intervention strategies, onset of schizophrenia and bipolar disorders is typically in late adolescence and early adulthood with the greatest burden occurring during ages 25–50,1 when work and marriage typically occur. Finally, the financial burden associated with schizophrenia is severe, with global economic costs ranging from $94 million to ...

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