Two of the largest randomized control trials of Prozac as an intervention for restrictive and repetitive behaviors were published recently.  They both coincidentally found no effect on the core features of autism, nor clinician rated improvement.  What they did find is a big placebo effect.  That is the behaviors of the participants changed even if they thought they might be getting the medication, but were actually getting an empty pill.  This is a big problem in research in studying medications across mental health.  So why is Prozac so popular?  And when it comes to some features of autism, is the placebo effect so bad?
https://www.ncbi.nlm.nih.gov/pubmed/31638682 
https://www.ncbi.nlm.nih.gov/pubmed/31267292