Why is late adolescence and early adulthood the peak years for developing schizophrenia?

Greater demand. Subtle processing irregularities may not be identified in earlier years when the environmental demands were not as complex, , and individuals are developing skills to meet the needs of theri irregular processing instead of developing more typical skills so with the adolescent brain pruning thier function is more compromised that is functional.
Pruning. After birth, the brain begins a process of cell death called pruning. This process allows the brain to create specific patterns of neuron connections that drive our ability to learn. In adolescence, this pruning speeds up. However, individuals with schizophrenia have even faster pruning and this leads to the illness starting around this time.