Contrasting scenarios in which index event bias is or is not expected, based on the likely causality of exposures for disease onset.

Solid black lines indicate assumed causality. Absent lines indicate assumed lack of causality. Dashed black line indicates induced association. Absent dashed line indicates lack of induced association. Boxes indicate a variable that has been conditioned on. CHD, coronary heart disease; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; SNP, single nucleotide polymorphism.