All five, scientists now say, share common genetic roots.
Working with a global team of scientists, Dr. Anil Malhotra, an investigator at the Feinstein Institute for Medical Research in Manhasset, said DNA pathways common to all five have been clearly traced in the brain.
For decades, he said, doctors thought there was a relationship among the conditions and at one time, many years ago, referred to autism as childhood schizophrenia.
Now, with the telltale genes in hand, Malhotra said medical investigators have scientific assurances they've been on the right genetic trail all along.
"There are several commonalities and symptoms that these conditions share, such as a presence of language disturbance, the presence of mood problems and depression," said Malhotra, who is also director of psychiatric research at Zucker Hillside Hospital, North Shore-LIJ's behavioral-health center in Queens.
A vast portion of the research in which Malhotra is involved was reported in The Lancet, a medical journal, last week. But he and his collaborators have been working on the genetic links shared by autism spectrum disorders and other psychiatric conditions for years.
They will continue their research, he said, in a vast global project called the Psychiatric Genomics Consortium.
"We've had major hints of this for clinical reasons for a long time," Malhotra said of relationships among the five, "but this is some of the most compelling molecular genetic information to support an overlap."
Blood samples from patients throughout the region were used to pinpoint a genetic kinship among the five conditions.
All told, DNA samples collected worldwide amounted to more than 33,300 from people with the brain conditions and 27,888 who were free of them. Features shared among the five disorders were not seen in the control group.
Key in the journal report was a chemical link, an imbalance of calcium in brain cells.
Like Malhotra, other investigators in the genome consortium see the possibility for new, gene-specific medications.
"Significant progress has been made in understanding the genetic risk factors underlying [these] psychiatric disorders," Dr. Jordan Smoller of Massachusetts General Hospital in Boston said in a statement.
Smoller, a lead investigator in the genome consortium, suggests the DNA findings could pave the way to a reclassification of the conditions based on DNA.
A fiery debate, which has yet to be extinguished, arose over the elimination of Asperger syndrome in the upcoming fifth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders. The volume is known as the diagnostic bible for mental health professionals.
When the DSM-V comes out in May, all autism-related conditions will be known as autism spectrum disorders.