What is Multiple complex developmental disorder?

Multiple complex developmental disorder is a research category, proposed to involve several neurological and psychological symptoms where at least some symptoms are first noticed during early childhood and persist throughout life. It was originally suggested to be a subtype of autistic spectrum disorders with co-morbid schizophrenia or another psychotic disorder; however, there is some controversy that not everyone with MCDD meets criteria for both PDD and psychosis. The term multiplex developmental disorder was coined by Donald J. Cohen in 1986.