Schizophrenia and autism were linked in many researchers’ studies. It was in the 1960s when medical professionals started to see these two disorders as separate conditions. Since 1980, Kanner’s so-called "early infantile autism" is listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM). It had a more accurate definition of autism in 1987. Since then, early infantile autism is called autism disorder. For the first time the DSM also introduced standardized criteria to diagnose autism. The fourth edition expanded the definition of autism and included milder cases of autism. Asperger’s syndrome was added as a type of autism in 1994.