Separation anxiety disorder is diagnosed when symptoms are excessive for the developmental age and cause significant distress in daily functioning. Symptoms may include: 
Recurrent and excessive distress about anticipating or being away from home or loved ones
Constant, excessive worry about losing a parent or other loved one to an illness or a disaster
Constant worry that something bad will happen, such as being lost or kidnapped, causing separation from parents or other loved ones
Refusing to be away from home because of fear of separation
Not wanting to be home alone and without a parent or other loved one in the house
Reluctance or refusing to sleep away from home without a parent or other loved one nearby
Repeated nightmares about separation
Frequent complaints of headaches, stomachaches or other symptoms when separation from a parent or other loved one is anticipated
 Separation anxiety disorder may be associated with panic disorder and panic attacks ― repeated episodes of sudden feelings of intense anxiety and fear or terror that reach a peak within minutes.