Definitions and Epidemiology

Psychosis describes syndromes that impair both thought content and thought process. Disturbances in thought content include perceptions that are not based in reality, whereas disturbances in thought process reflect thoughts that are disorganized and illogical in form. Psychotic symptoms include visual, tactile, or olfactory hallucinations; delusions; impairment of concentration and attention; and disorientation. Schizophrenia is the disorder that is most often associated with psychosis. Bipolar disorder, major depression, and substance abuse are examples of psychiatric diagnoses that can also cause symptoms of acute psychosis.

The 1-year prevalence of the schizophrenic disorders is 1.1%. One in every 100 persons in the United States suffers from psychotic symptoms.¹ Episodes of psychosis are generally precipitated or exacerbated by psychosocial stressors. Psychosis may be acute or chronic. As is often the case with the first manifestation of schizophrenia, acute psychotic episodes prompt patients to seek emergency care for their bizarre behavior or troubling perceptions.

Pathophysiology

The dominant theory used to explain the pathophysiology of psychotic thought is the dopamine hypothesis. This theory suggests that psychosis is probably the result of excessive dopamine transmission in the mesolimbic pathway of the brain. Evidence offered for the behavioral influence of this neurotransmitter is based on the observed effects of antipsychotic medications on dopamine pathways of the brain. Dopamine receptor antagonists (D₂ receptor antagonists) improve disturbed thoughts in psychotic patients. The efficacy of the typical (first-generation) antipsychotic agents depends on the degree to which these drugs block D₂ receptor activity.

Competing theories that describe the pathophysiology of psychosis are also based on neurotransmitter activity. These theories generally cite the effects and interplay of serotonin and glutamate with dopamine.

Presenting Signs and Symptoms

Most psychotic disorders are initially manifested in adolescence and young adulthood. The median age at the onset of symptoms of a psychiatric disorder is 16 years. By the age of 38 years, symptoms will have developed in more than 90% of patients with a mental disorder.¹ The typical example of a newly psychotic patient is a young person brought to the emergency department (ED) by family or friends who are concerned about the patient’s bizarre behavior or unusual beliefs. The “positive” symptoms of psychosis, including hallucinations and delusions, are often more obvious and distressing than the “negative” symptoms, which are affective and generally develop more insidiously.

The key features of psychotic symptoms are perceptions and beliefs that are not based in reality. Such disturbances include hallucinations, illusions, and delusions.

Hallucinations are sensory perceptions that are apparent only to the patient experiencing them. Auditory hallucinations are the most common and are typically described as hearing voices of people who are not present. Hallucinations that involve other senses (visual, olfactory, or tactile) are less frequently reported and may be the result of medical illness. Patients who are hallucinating appear to be preoccupied or distracted as they respond to internal stimuli.

Illusions refer to misperceptions about a patient’s surroundings, whereas hallucinations are wholly internal and are not prompted by an environmental stimulus.

Delusions are misinterpretations of events or perceptions that lead psychotic patients to erroneously attribute experiences to unlikely or bizarre beliefs. Unlike cultural beliefs, delusions are explanations that are not shared by others. Most delusions involve a sense of control. For example, patients with delusions of persecution may believe that they are under hostile surveillance or that people are plotting against them. Grandiose delusions cause patients to believe that they are endowed with supernatural powers or are able to affect events outside their sphere of influence.

Psychosis may also be manifested as disorganization in thought process, with patients expressing ideas and words that are not coherently linked. Thoughts are described as tangential when the patient switches from one topic to another without logical association. When thoughts become more disorganized, the patient may start using neologisms, or self-created nonsense words. Speech may later regress into an incomprehensible jumble of unassociated phrases that may be described as a word salad.

The negative symptoms of psychosis reflect a loss of function, such as the ability to express affect, generate speech, or become motivated. These symptoms may be overlooked because they are often perceived as less obviously disturbing than “positive” symptoms, but they can also significantly impair the lives of psychotic patients.

Differential Diagnosis

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