While both The Peter Pan Syndrome and The Alice in Wonderland Syndrome do exist, they are commonly associated with adults. Given that premise, I will concentrate on how the settings of the stories appeal to juveniles and affect their development.
The setting of Peter Pan is the fantasy world of Neverland, where one never grows up. It is a wonderful fantasy to find and live in a place where responsibilities are of no consequence. If a juvenile develops into an adult and clings to these notions, it creates severe problems with incorporating oneself into the actual world of adulthood. Being expected to actually solve one's own problems and effect a responsible solution to adult situations can lead to anger, frustration, and a general inability to function.
The setting of Alice in Wonderland is the fantasy world of Wonderland, where time and perception are an illusion. It is an interesting place to visit because one never knows what to expect. This is much like a child's everyday life. They are too small for some situations and too big for others. They are constantly at the mercy of their ever-changing environment. As they grow and develop, they must learn to integrate their perception of reality with reality itself. Otherwise, they may become delusional and paranoid.