Figure.

Schematic of schizophrenia as a pathway disease. Genetic variants at many loci encode the components of a pathway or pathways. Many risk loci can be affected, resulting in a disease pathway greatly modified owing to polygenetic variation. When a few risk loci are affected, there may be limited impact on the disease pathway. This pathway itself—in conjunction with environmental risk factors or other factors—mediates risk of schizophrenia.