Changes in many genes, each with a small effect, may underlie susceptibility to many common diseases, including cancer, obesity, diabetes, heart disease, and mental illness. In people with a genetic predisposition, the risk of disease can depend on multiple factors in addition to an identified genetic change.These include other genetic factors (sometimes called modifiers) as well as lifestyle and environmental factors.he World Health Organization offers information about genetic predisposition to several common diseases, including cancer, diabetes, cardiovascular disease, and asthma. Genetic Alliance UK offers a fact sheet on genetic predisposition to common genetic diseases.