I think that JW children have an underlying sense/fear that they can never live up to (or don't want to live up to) the standards they've been taught that God requires for them to be spared the impending destruction that is always looming over their heads.
Telling children that the world is going to end in destruction is a form of child abuse, because they are black and white thinkers and don't have the psychological coping skills to cope with the idea of world destruction. Some children may conclude that the only way for them to avoid the future doom, is to die now. Over time, this underlying conclusion may become a habitual and automatic thought that runs through their subconscious minds during times of high stress.
There are therapies designed to help individuals retrain or gain control over their subconscious thoughts and identify them as they happen. These thoughts may eventually go away entirely but sometimes they come back during stressful times in ones life. Having the ability to identify them as they occur and replace them with positive thoughts, is key.