Table 1

“Best estimate” effect sizes of various genetic and environmental risk factors for schizophrenia (expressed as odds ratios or relative risks)

Category of risk factorSpecific risk factorsBest estimate of effect size
Genetic1-150 Monozygotic twin of schizophrenic  patients46
Dizygotic twin of schizophrenic patient14
Child/sibling of schizophrenic patient10
Childhood developmental
Delayed milestones

Speech problems3
Prenatal and postnatal environment Pre-eclampsia9
Perinatal brain damage7
Rhesus incompatibility3
“Unwanted” pregnancy2
Severe undernutrition (1st trimester)2
Maternal influenza (2nd trimester)2
  • 1-150 Relative risks; odds ratios.