Diabetes: Causes...

Genetics

Both type 1 and type 2 diabetes are at least partly inherited.

Type 1 diabetes appears to be triggered by some (mainly viral) infections, or in a less common group, by stress or environmental exposure (such as exposure to certain chemicals or drugs).

There is a stronger inheritance pattern for type 2 diabetes. Those with first-degree relatives with type 2 have a much higher risk of developing type 2, increasing with the number of those relatives.

Obesity

Another risk factor is obesity, particularly central obesity (i.e., that in and around abdominal organs), which is found in approximately 85% of North American patients diagnosed with this type, so some experts believe that inheriting a tendency toward obesity also contributes.