A number of reasons and theories exist to explain the development of SAD. Genetics seems to play a role because children diagnosed with SAD are more likely to have a family member with an anxiety disorder. Some research connects children with SAD to mothers who have panic disorder. Learning most likely plays a role as children observe their parents who have attitudes about going out into the world, and model poor coping skills in dealing with life stressors.

It is believed by experts that separation anxiety disorder can develop from a major life transition or a significantly stressful or traumatic experience at a young age, which includes: loss of parent through divorce, a long separation because either the parent or child is hospitalized, the parent is in jail, or away because of military duty, etc. Other experiences are moving and going to a new school. Trauma such as physical, sexual, and verbal abuse, witnessing violence, and being a victim of war or natural disaster may bring on SAD.

Biological theories are looking into chemical imbalances in levels of serotonin and norepinephrine, as well as other hormones and respiration. Some researchers are studying influences during pregnancy such as endocrine release. Others are looking at what happens to children when they lose or are separated from the parent in infancy and brought up by someone else—these studies show a strong link to development of anxiety symptoms, depression, and learned helplessness. Numerous causes exist for the development of separation anxiety disorder and treatment plans must look at biological, genetic, psychological, and environmental factors.

The effects of having a child with SAD can be difficult to cope with. It is heartbreaking to watch your child suffer, but at the same time you may feel afraid, frustrated, annoyed, angry, disappointed, and exhausted. If your child has SAD, he or she will most likely take up a great deal of time and attention. Children with SAD often need constant reassurance if a separation is imminent. Siblings may feel resentful or ashamed of their sibling's behavior. You may argue with your spouse about your reactions and responses to your child's behavior, and maybe even blame each other. Your child may not develop emotionally in a healthy way because of the fears, or go on to develop other anxiety disorders. But professional help, proper diagnosis, treatment, and education can make a positive change.