Multifactorial Neurodevelopmental Model

Current evidence suggests that a multifactorial neurodevelopmental model best explains the development of schizophrenia, with multiple genetic and environmental exposures playing roles (McClellan & Stock, 2013).The most important risk factors for vulnerability to schizophrenia are genetic factors where family, twin, and adoption studies support a strong genetic component (Lewis & Lieberman, 2000; McClellan & Stock, 2013; Niemi, Suvisaari, Tuulio-Henriksson, & Lönnqvist, 2003).

Family, twin, and adoption studies have demonstrated that the morbid risk of schizophrenia in relatives correlates with the degree of shared genes (Lewis & Lieberman, 2000).

Heritability estimates from the most recent twin studies are as high as 83%. (Niemi, Suvisaari,

Tuulio-Henriksson, & Lönnqvist, 2003). Among dizygotic twins and other siblings, the rate of concordance of schizophrenia is approximately 5-15%, and research indicates that in general, the concordance between monozygotic twins has reached over 50%, whether they were reared together or apart (Bromet & Fennig, 1999; Lewis & Lieberman, 2000; McClellan & Stock, 2013).
There have been other factors found that may play a role in the etiology of schizophrenia.

These include environmental factors which may be exposure to infectious, autoimmune, toxic, or traumatic insults and stress during gestation or childhood, marijuana use, and even immigration (Lewis & Lieberman, 2000; McClellan & Stock, 2013). In addition, during pregnancy the risk of developing schizophrenia increases when there have been complications during the pregnancy (Bromet & Fennig, 1999; McClellan & Stock, 2013; Niemi, Suvisaari, Tuulio-Henriksson, & Lönnqvist, 2003). In regards to social class and the development of schizophrenia, hypotheses include adverse environmental conditions that precipitate the onset and that social selection or social drift that may explain the relationship (Bromet & Fennig, 1999). The season of birth may also be related to schizophrenia onset. The proportion of people with schizophrenia born during the winter and spring months are excessively greater with about a 5% to 15% higher rate than at other times of the year (Bromet & Fennig, 1999; Lewis & Lieberman, 2000). Stress may also be a factor where maternal stress during pregnancy, life events and familial strains have been found to play a role in schizophrenia ( Bromet & Fennig, 1999). In regards to geographic location, being raised in an urban environment is a risk factor for schizophrenia, where those raised in an urban area had a 1.65 times greater risk of schizophrenia than those raised in

rural areas (Bromet & Fennig, 1999). Lastly, Individuals with schizophrenia also tend to inhabit lower socioeconomic strata (Lewis & Liebeman, 2000).