Section VII: Psychiatric Disorders

Thought Disorders

OBJECTIVES

PREVALENCE & BURDEN

Schizophrenia, the most common primary psychotic disorder, has a lifetime prevalence of approximately 1% worldwide, is equally common in males and females, and affects individuals from all racial and ethnic groups. The typical age of onset is in late adolescence to early adulthood, with females having an illness onset of approximately 5 to 10 years later. Prepubescent onset is rare, but those who present with early-onset schizophrenia have a more severe illness course. Late-onset schizophrenia after the age of 45 years is more common in females. The prevalence of schizophrenia is higher in densely populated areas and in developed nations. Life expectancy in patients is 10 to 20 years lower relative to the general population, which is attributed to increased rates of suicide (6% completed suicide rate), accidents, smoking, and poor physical health. Direct and indirect costs in the United States are estimated at about $100 billion annually, with productivity losses being the largest component of the overall societal cost.

MAJOR THOUGHT DISORDERS

Schizophrenia

Schizophrenia is a complex, heterogeneous syndrome believed to be multifactorial, with genetic and environmental components. Patients vary widely in their symptomatology, course of illness, and treatment response, to the point that the diagnosis may identify individuals who share few or no symptoms in common. The validity of traditional clinical subtypes (eg, paranoid schizophrenia, catatonic schizophrenia) as nosologic entities has been questioned, and their prognostic value is limited. Dimensional models of psychosis suggest that symptoms and disease course are better explained in terms of continuous distributions. The psychopathology can be described along the following symptom domains: (1) positive symptoms, which include delusions, hallucinations, and disorganization of thought and speech; (2) negative symptoms, which include apathy, alogia, poor attention, flat affect, and anhedonia; and (3) cognitive deficits, which include working memory and episodic memory deficits, impairment in executive function, and decreased attention span. Negative symptoms can be divided into primary and secondary negative symptoms. Primary symptoms are regarded as part of the illness, whereas secondary negative symptoms have other causes, such as preoccupation with hallucinations or delusions, suspicious withdrawal, depression, medication side effects, or social isolation. Approximately 25% to 30% of patients suffer from persistent primary negative symptoms, also known as the deficit syndrome (see later discussion). Patients with significant negative symptoms may have poor awareness of their symptoms. Cognitive deficits are present in approximately 75% to 85% of all patients; the extent is variable, but patients typically score about a standard deviation lower on standardized assessments than would be expected for the general population. Memory is the cognitive ...