Reactive attachment disorder usually occurs due to early childhood trauma and is often the result of a break in the bond between parent and child.
The above can happen when parents are incarcerated or die unexpectedly; it can also occur when children are separated from their parents for another reason and get placed into care.
In the above scenarios, the emotional connection is not made between child and parent or gets severed at an early age (usually before the age of five).
A child with reactive attachment disorder is usually withdrawn and often experiences severe depressive symptoms.