Multifactorial genetic disorders, or complex traits, result from several genes in combination with lifestyle and environmental influences. Multifactorial disorders include diseases like diabetes, many cancers, heart disease, and asthma. Multifactorial disorders account for the largest group of genetic conditions, both in numbers and the impact that they have on child health and the health care system as a whole.

Autism is an example of a multifactorial disorder that is largely caused by genetic inheritance. Read Autism linked primarily to common gene variants for more information.