HPPD MOM

My son at age 18, used LSD a handful of times. He came to me shortly thereafter and told me his trip would not end. He told he thought he had HPPD. Since that time, 4 years ago, I have sought help from no less than 50 specialists on the east coast of the USA, with literally no help. His GP put him on Clonipin, and it lessened his anxiety for a bit, but he is "shark-bit" from any drug, he decided to get off of it, and did. As a result, he experiences debilitating HPPD symptoms including VS, trailing, flashbacks and crippling panic attacks. As a single mom, it is heartbreaking, and I have no one to talk to about this. Any ideas on what I can do to help my only son? Before this, he as an honor student, star athlete, and the favorite kid at school. He now is a shell of what he was before, always sad, crying and very dark. Thank you.