INTRODUCTION & EPIDEMIOLOGY
Psychosis has been defined as a "fundamental derangement of the mind characterized by defective or lost contact with reality."1 The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V),2 defines psychotic disorders as those that include abnormalities in one or more of five domains: hallucinations, delusions, disorganized or abnormal motor behavior, disorganized thinking, and negative symptoms. The hallmark of these psychoses, schizophrenia, has a worldwide prevalence of 0.5% to 1%3 and affects approximately 2.4 million adults in the United States.4 Considered one of the leading causes of chronic incapacity, the term schizophrenia, meaning "split mind," was coined by Eugene Bleuler in 1911.5 The economic burden of schizophrenia in the United States in 2002 was estimated at $62.7 billion6 and typically accounts for 1.5% to 3% of the total national healthcare expenditure, with a high incidence of ED utilization.7
The assessment of the psychotic patient presenting to the ED can be challenging, because patients may be agitated, combative, uncooperative, or unable to provide any history. The goals of evaluation are multiple. First, minimize any potential harm to the patient and ensure the safety of the ED staff and other patients. In the case of an aggressive or violent patient, this may require the use of verbal de-escalation techniques or physical or chemical restraints. Second, assess for any coexisting or confounding medical or traumatic conditions. Emergency physicians are gatekeepers to the psychiatric world, because once the patient is funneled into the psychiatric treatment realm, organic conditions may become more difficult to identify and treat. Psychiatric conditions contribute to increased mortality from comorbid medical conditions as compared to the general population.8 Finally, aim to optimize the treatment of the patient's underlying psychiatric illness, either by connecting him or her with the appropriate inpatient or outpatient resources, or, when possible, by contacting his or her psychiatrist.
Both environmental and genetic factors contribute to the schizophrenia spectrum of disorders. The incidence of schizophrenia is higher in those growing up in urban areas9 and in certain minority ethnic groups,10 and the disorders have been linked to a spectrum of risk alleles. There is also overlap between the alleles associated with schizophrenia and those associated with other disorders such as autism and bipolar disorder.11
Traditionally, the dopamine hypothesis, wherein excessive dopamine leads to the pathophysiology of schizophrenia, has been the dominant theory.12 Now, it is thought that dopamine acts as the common final pathway of a wide variety of predisposing factors, either environmental, genetic, or both, that lead to the disease. Other neurotransmitters, such as glutamate and adenosine, may also collaborate with dopamine to give rise to the entire picture of schizophrenia.13
Features of psychoses include hallucinations, delusions, disorganized thinking, and negative symptoms.