Experiences and heredity determine each person’s risk for developing an anxiety disorder.

This is because both environment and genetic makeup have an impact on brain chemistry and stress tolerance — factors that contribute to whether someone experiences normal, mild anxiety symptoms or is at risk for a full-blown disorder.

On average, genetics account for approximately 30 percent to 40 percent of any individual’s risk for severe anxiety.

Whether a parent modeled healthy responses to stress or taught a child anxious reactions also shapes the ability to cope with stress.

The anxiety people experience may also differ according to age. Because older adults tend to develop chronic illnesses, their anxiety may be associated with declining health.

In addition, older people are at risk for memory decline and dementia, both of which are associated with anxiety.

Physical illnesses and medication side effects can also lead to anxiety symptoms. For instance, diabetics who take too much insulin can experience acute anxiety attacks from sudden drops in blood sugar.