Hockenbury Discovering Psychology 5th txtbk

Schizophrenia569• Men in the 45-to-49 age group who fathered children were twice as likely tohave offspring with schizophrenia as compared to fathers age 25 and under.• Men in the 50-plus age range were three times more likely to produce offspringwith schizophrenia.• More than one-quarter of the schizophrenia cases could be attributed to thefather’s age.• The mother’s age appeared to play no role in the development of schizophrenia.Clearly, then, paternal age is a potential risk factor. However, it’s important to keepin mind that three-quarters of the cases of schizophrenia in this study were not associatedwith older paternal age.Environmental FactorsThe Viral Infection TheoryOne provocative theory is that schizophrenia might be caused by exposure to an influenzavirus or other viral infection during prenatal development or shortly afterbirth. A virus might seem an unlikely cause of a serious mental disorder, but virusescan spread to the brain and spinal cord by traveling along nerves. According to thistheory, exposure to a viral infection during prenatal development or early infancy affectsthe developing brain, producing changes that make the individual more vulnerableto schizophrenia later in life.There is growing evidence to support the viral infection theory. In one compellingstudy, psychiatrist Alan S. Brown and his colleagues (2004) compared storedblood samples of 64 mothers of people who later developed schizophrenia with amatched set of blood samples from women whose children did not develop schizophrenia.Both sets of blood samples had been collected years earlier during thewomen’s pregnancies. After analyzing the blood samples for the presence of influenzaantibodies, Brown and his colleagues (2004) found that women who hadbeen exposed to the flu virus during the first trimester had a sevenfold increased riskof bearing a child who later developed schizophrenia.Previous studies using maternal recall and the dates of influenza epidemics havedemonstrated similar findings: Children whose mothers were exposed to a flu virusduring pregnancy, especially during the first or second trimester, show an increasedrate of schizophrenia (Carter, 2008; Yudofsky, 2009). A related finding is that schizophreniaoccurs more often in people who were born in the winter and springmonths, when upper respiratory infections are most common (Torrey, 2006).Abnormal Brain StructuresLoss of Gray MatterResearchers have found that about half of the people with schizophrenia showsome type of brain structure abnormality. The most consistent finding has been theenlargement of the fluid-filled cavities, called ventricles, located deep withinthe brain (Fraguas & others, 2008). However, researchers are not certainhow enlarged ventricles might be related to schizophrenia. Other differencesthat have been found are a loss of gray matter tissue and lower overall volumeof the brain (Cahn & others, 2009). As we discussed in Chapter 2, graymatter refers to the glial cells, neuron cell bodies, and unmyelinated axonsthat make up the quarter-inch-thick cerebral cortex.To investigate the neurological development of schizophrenia, neuroscientistPaul M. Thompson and his colleagues (2001) undertook a prospectivestudy of brain structure changes in 12 adolescents with early-onsetchildhood schizophrenia. The six females and six males had all experiencedschizophrenic symptoms, including psychotic symptoms, before the age of12. The intent of the study was to provide a visual picture of the timing,rates, and anatomical distribution of brain structure changes in adolescentswith schizophrenia.Identical Twins but Not Identical BrainsDavid and Steven Elmore are identicaltwins, but they differ in one important respect—Steven(right) has schizophrenia.Behind each is a CAT scan, which revealsthat Steven’s brain is slightly smaller, withless area devoted to the cortex at the topof the brain. Steven also has larger fluidfilledventricles, which are circled in red onhis brain scan. As researcher Daniel Weinberger(1995) commented, “The part ofthe cortex that Steven is missing serves asperhaps the most evolved part of the humanbrain. It performs complicated taskssuch as thinking organized thoughts. Thismight help explain why paranoid delusionsand hallucinations are characteristic ofschizophrenia.”