Amanda Bynes got a side benefit from intensive therapy for schizophrenia and bipolar disorder ... a bangin' body.
Sources familiar with Amanda's treatment tell us ... doctors told her daily exercise was an important part of regaining balance and calm, and it's very clear Amanda has been a good patient.
So this week she's been chillin' in Mexico for Spring Break -- doing it up CABO STYLE.
The trip was a present from her parents, who chaperoned her ... meaning no beer, body shots or wet T-shirt contests.
She's on break from her fashion design school, where she's done incredibly well.
Amanda -- who turned 28 Thursday -- clearly learned a thing or 2 in school, 'cause she looks great in a green bikini!