Schizophrenia
I. Definition
Schizophrenia is a syndrome of unknown etiology characterized by disturbances in cognition, emotion, perception, thinking, and behavior. Schizophrenia is well established as a brain disorder, with structural and functional abnormalities visible in neuroimaging studies and a genetic component, as seen in twin studies. The disorder is usually chronic, with a course encompassing a prodromal phase, an active phase, and a residual phase. The active phase has symptoms such as hallucinations, delusions, and disorganized thinking. The prodromal and residual phases are characterized by attenuated forms of active symptoms, such as odd beliefs and magical thinking, as well as deficits in self-care and interpersonal relatedness. Since the 1970s, the number of schizophrenic patients in hospitals has decreased by over 50% (deinstitutionalization). Of those being treated, over 80% are managed as outpatients. Although schizophrenia is discussed as if it is a single disease, it probably comprises a group of disorders of heterogeneous etiology. A brief history of the disorder is to be found in Table 12-1.
II. Epidemiology
A. Incidence and prevalence.
In the United States, the lifetime prevalence of the disease is about 1%, which means that 1 in 100 persons will develop the disorder during his or her lifetime. It is found in all societies and in all geographic areas. Worldwide, 2 million new cases appear each year. In the United States, only about 0.05% of the total population is treated for schizophrenia in any single year, and only about half of all patients obtain treatment of any kind. There are over 2 million persons suffering from schizophrenia in the United States.
B. Gender and age.
Equally prevalent between men and women; usually onset is earlier in men. Peak age of onset is between 15 and 35 years (50% of cases occur before age 25). Onset before age 10 (called early-onset schizophrenia) or after age 45 (called late-onset schizophrenia) is uncommon.
C. Infection and birth season.
Persons born in winter are more likely to develop the disease than those born in spring or summer (applies to both Northern and Southern Hemispheres). Increased in babies born to mothers who have influenza during pregnancy.
D. Race and religion.
Jews are affected less often than Protestants and Catholics, and prevalence is higher in nonwhite populations.
E. Medical and mental illness.
Higher mortality rate from accidents and natural causes than in general population. Leading cause of death in schizophrenic patients is suicide (10% kill themselves). Over 40% of schizophrenic patients abuse drugs and alcohol. Treatment with antipsychotic
agents increase the risk of developing diabetes and the metabolic syndrome.
agents increase the risk of developing diabetes and the metabolic syndrome.
Table 12-1 History of Schizophrenia | |||
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F. Socioeconomics.
More common among lower rather than higher socioeconomic groups; high prevalence among recent immigrants; most common in cities with over 1 million population. Direct and indirect costs resulting from schizophrenic illness in the United States are over $100 billion per year.
III. Etiology
Owing to the heterogeneity of the symptomatic and prognostic presentations of schizophrenia, no single factor is considered causative. The stress diathesis model is most often used, which states that the person in whom schizophrenia develops has a specific biological vulnerability, or diathesis, that is triggered by stress and leads to schizophrenic symptoms. Stressors may be genetic, biological, and psychosocial or environmental.
A. Genetic.
Both single-gene and polygenic theories have been proposed (Table 12-2). Although neither theory has been definitively substantiated, the polygenic theory appears to be more consistent with the presentation of schizophrenia.
Consanguinity. Incidence in families is higher than in the general population, and monozygotic (MZ) twin concordance is greater than dizygotic (DZ) (Table 12-3).
Adoption studies
The prevalence of schizophrenia is greater in the biological parents of schizophrenic adoptees than in adoptive parents.
MZ twins reared apart have the same concordance rate as twins reared together.
Table 12-2 Features Consistent with Polygenic Inheritancea
- Disorder can be transmitted with two normal parents.
- Presentation of disorder ranges from very severe to less severe.
- More severely affected persons have a greater number of ill relatives than mildly affected persons do.
- Risk decreases as the number of shared genes decreases.
- Disorder present in both mother’s and father’s side of family.
aThe number of affected genes determines a person’s risk and symptomatic picture.
Table 12-3 Prevalence of Schizophrenia in Specific Populations
Population
Prevalence
General population
1–1.5
First-degree relativea
10–12
Second-degree relative
5–6
Child of two schizophrenic parents
40
Dizygotic twin
12–15
Monozygotic twin
45–50
aSchizophrenia is not a sex-linked disorder; it does not matter which parent has the disorder in terms of risk.
- Disorder can be transmitted with two normal parents.
Rates of schizophrenia are not increased in children born to unaffected parents but raised by a schizophrenic parent.
B. Biological
Dopamine hypothesis. Schizophrenic symptoms may result from increased limbic dopamine activity (positive symptoms) and decreased frontal dopamine activity (negative symptoms). Dopaminergic pathology may be secondary to abnormal receptor number or sensitivity, or abnormal dopamine release (too much or too little). The theory is based on psychotogenic effects of drugs that increase dopamine levels (e.g., amphetamines, cocaine) and the antipsychotic effects of dopamine receptor antagonists (e.g., haloperidol [Haldol]). Dopamine receptors D1 through D5 have been identified. The D1 receptor may play a role in negative symptoms. Specific D3 and D4 receptor agonist and antagonist drugs are under development. Levels of the dopamine metabolite homovanillic acid may correlate with the severity and potential treatment responsiveness of psychotic symptoms. Limitations of the theory include the responsiveness of all types of psychoses to dopamine-blocking agents, which implicates dopaminergic abnormalities in psychoses of multiple causes. The complex interplay of different neurotransmitter systems, including serotonin–dopamine interactions, in addition to the effects of amino acid neurotransmitters on monoamine render single-neurotransmitter theories incomplete.
Norepinephrine hypothesis. Increased norepinephrine levels in schizophrenia lead to increased sensitization to sensory input.
γ-Aminobutyric acid (GABA) hypothesis. Decreased GABA activity results in increased dopamine activity.
Serotonin hypothesis. Serotonin metabolism apparently is abnormal in some chronically schizophrenic patients, with both hyperserotoninemia and hyposerotoninemia being reported. Specifically, antagonism at the serotonin 5-HT2 receptor has been emphasized as important in reducing psychotic symptoms and the development of movement disorders related to D2 antagonism. Research on mood disorders has implicated serotonin activity in suicidal and impulsive behavior, which schizophrenic patients can also exhibit.
Glutamate hypothesis. Hypofunction of the glutamate N-methyl-D-aspartate (NMDA)-type receptor is theorized to cause both positive and negative symptoms of schizophrenia based on the observed psychotogenic effects of the NMDA antagonists phencyclidine and ketamine (Ketalar), in addition to the observed therapeutic effects (in research settings) of the NMDA agonists glycine and D-cycloserine.
Neurodevelopmental theories. There is evidence of abnormal neuronal migration during the second trimester of fetal development. Abnormal neuronal functioning may lead to the emergence of symptoms during adolescence.
C. Psychosocial and environmental
Family factors. Patients whose families have high levels of expressed emotion (EE) have higher relapse rate than those whose families have low EE levels. EE has been defined as any overly involved, intrusive behavior, be it hostile and critical or controlling and infantilizing. Relapse rates are better when family behavior is modified to lower EE. Most observers believe that family dysfunction is a consequence, rather than a cause, of schizophrenia.
Other psychodynamic issues. Knowing what psychological and environmental stresses are most likely to trigger psychotic decompensation in a patient helps the clinician to address these issues supportively and, in the process, helps the patient to feel and remain more in control.
D. Infectious theory.
Evidence for a slow virus etiology includes neuropathological changes consistent with past infections: gliosis, glial scarring, and antiviral antibodies in the serum and cerebrospinal fluid (CSF) of some schizophrenia patients. Increased frequency of perinatal complications and seasonality of birth data also support an infectious theory.
IV. Diagnosis, Signs, and Symptoms
Schizophrenia is a disorder whose diagnosis is based on observation and description of the patient. Abnormalities are often present on most components of the mental status examination. There are no pathognomonic signs or symptoms. According to the text revision of the fourth edition of the Diagnostic Statistical Manual of Mental Disorders (DSM-IV-TR), at least two of the following five signs or symptoms must be present for at least 1 month: (1) hallucinations, (2) delusions, (3) disorganized speech, (4) disorganized behavior, or (5) negative symptoms (e.g., flat affect, abulia). The signs and symptoms should be present for at least 6 months for the disorder to be confirmed (Table 12-4). Other diagnostic features of schizophrenia are listed below.
A. Overall functioning.
Level of functioning declines or fails to achieve the expected level.
B. Thought content.
Abnormal (e.g., delusions, ideas of reference, poverty of content). Delusion and hallucinations are not necessary to make the diagnosis if other signs and symptoms are present.
Table 12-4 DSM-IV-TR Diagnostic Criteria for Schizophrenia | |||
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C. Form of thought.
Illogical (e.g., derailment, loosening of associations, incoherence, circumstantially, tangentiality, overinclusiveness, neologisms, blocking, echolalia—all incorporated as a thought disorder).
D. Perception.
Distorted (e.g., hallucinations: visual, olfactory, tactile, and, most frequently, auditory).
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