There have been a number of studies indicating that schizophrenia is a complex genetic disorder. Which of the following observations are most consistent with this hypothesis? 1. Siblings of individuals with schizophrenia have an elevated risk of developing schizophrenia.
2. In monozygotic twins, if one twin has schizophrenia, it is very rare that the other is affected.
3. Malnutrition in utero and certain infections may increase risk of schizophrenia.
4. Schizophrenia follows an autosomal recessive inheritance pattern.