I find the other answer highly unknowledgeable and completely wrong. I am in my 30's and have high functioning autism. Charlie is just like me. He is definitely on the spectrum. High functioning means he is very intelligent and therefore we are able to learn behaviours.
A lot of high functioning autistic people have a gift that many cannot understand. For example, he said to the psychiatrist it's everyone else's pain he feels and sees and he wants it to stop. It feels so extreme, so intense, like fire rolling all over your soul, and all you want to do is make that other person happy and take their pain away because it physically hurts us so much.
When I hug some friends I say they feel like marshmallows, when I hug a certain person it feels like barbed wire I hate it. I can feel another person's pain and fears across the room and it's suffocating, like superman experiences. It's exhausting. It has a lot to do with the emotions from the other person that we are feeling. Yes, sometimes we cannot differentiate what it means, but most of the time we can, and it is real, so real.
Watching this film was like watching my own life in another person. Please don't tell people it's unlikely he's on the spectrum, just look at the modern day movies of Sherlock Holmes. He is 100% high functioning autistic and look at all of the accurate and emotional observations he makes, yet goes home and breaks down. That is because we use all our energy to appear 'normal' during the day, but when we go home it's our safe place and we can let down our guards.
Just because low functioning autistic people cannot differentiate between emotions, doesn't mean that high functioning Aspies can't. Autism is a variation of social and sensory issues, the key word being variation.