Hockenbury Discovering Psychology 5th txtbk

Schizophrenia567The Prevalence and Course of SchizophreniaEvery year, about 200,000 new cases of schizophrenia are diagnosed in the UnitedStates, and annually, approximately 1 million Americans are treated for schizophrenia.All told, about 1 percent of the U.S. population will experience at least oneepisode of schizophrenia at some point in life (Rado & Janicak, 2009). Worldwide,no society or culture is immune to this mental disorder. Most cultures correspondvery closely to the 1 percent rate of schizophrenia seen in the United States (Combs& Mueser, 2007).The onset of schizophrenia typically occurs during young adulthood (Tarrier,2008; Gourion & others, 2005). However, the course of schizophrenia is markedby enormous individual variability. Even so, a few global generalizations are possible(Malla & Payne, 2005; Walker & others, 2004). The good news is that about onequarterof those who experience an episode of schizophrenia recover completely andnever experience another episode. Another one-quarter experience recurrentepisodes of schizophrenia but often with only minimal impairment in the ability tofunction.Now the bad news. For the rest of those who have experienced an episode of schizophrenia—aboutone-half of the total—schizophrenia becomes a chronic mental illness,and the ability to function may be severely impaired. The people in this last categoryface the prospect of repeated hospitalizations and extended treatment. Thus,chronic schizophrenia places a heavy emotional, financial, and psychological burdenon people with the disorder, their families, and society (Combs & Mueser, 2007).Explaining SchizophreniaSchizophrenia is an extremely complex disorder. There is enormous individual variabilityin the onset, symptoms, duration, and recovery from schizophrenia. So itshouldn’t come as a surprise that the causes of schizophrenia seem to be equallycomplex. In this section, we’ll survey some of the factors that have been implicatedin the development of schizophrenia.Genetic FactorsFamily, Twin, Adoption, and Gene StudiesStudies of families, twins, and adopted individuals havefirmly established that genetic factors play a significantrole in many cases of schizophrenia. First, family studieshave consistently shown that schizophrenia tends tocluster in certain families (Choi & others, 2007; Torrey,2006). Second, family and twin studies have consistentlyshown that the more closely related a person is tosomeone who has schizophrenia, the greater the riskthat she will be diagnosed with schizophrenia at somepoint in her lifetime (see Figure 13.6). Third, adoptionstudies have consistently shown that if either biologicalparent of an adopted individual had schizophrenia, theadopted individual is at greater risk to develop schizophrenia(Tienari & others, 1994; Wynne & others,2006). And fourth, by studying families that display ahigh rate of schizophrenia, researchers have consistentlyfound that the presence of certain genetic variationsseems to increase susceptibility to the disorder(Fanous & others, 2005; Williams & others, 2005).Ironically, some of the best evidence that points togenetic involvement in schizophrenia—the almost 50percent risk rate for a person whose identical twin hasThe person with schizophrenia is your:You are the child of:First cousin 2%Uncle/Aunt 2%Nephew/Niece 4%Half-sibling 6%Sibling 9%Nonidentical twin 17%Identical twin 48%One parent withschizophrenia 17%010Figure 13.6 The Risk of DevelopingSchizophrenia Among Blood Relatives Therisk percentages shown here reflect thecollective results of about 40 studiesinvestigating the likelihood of developingschizophrenia among blood relatives. Asyou can see, the greatest risk occurs ifyou have an identical twin who hasschizophrenia (48 percent lifetime risk) orif both of your biological parents haveschizophrenia (46 percent lifetime risk).However, environmental factors, as wellas genetic ones, are involved in thedevelopment of schizophrenia.Source: Gottesman (1991), p. 96.Both parents withschizophrenia 46%2030Your lifetime risk of developing schizophrenia (percentage)4050