The invention relates to medicine, and more particularly to psychopharmacology, and is directed to an agent for treating and preventing autism spectrum disorders； said agent is glycine immobilized on detonation nanodiamond particles 2-10 nm in size, wherein the content of glycine is from 1 to 21±3 wt. %. The described agent improves the outcome of drug therapy and preventive treatment of autism in children and adults and expands the range of the effective and safe psychotropic medications.
