(CNN) -- Starting next year, the process of diagnosing autism may see drastic changes following the revision of the official guide to classifying psychiatric illnesses.
After years of reviewing and refining criteria used by psychiatrists and other experts to diagnose mental health disorders, the American Psychiatric Association board of trustees on Saturday approved major changes to the manual, better known as DSM-5.
The approval of the changes in the Diagnostic and Statistical Manual of Mental Disorders came during a meeting in Arlington, Virginia.
The DSM is considered the "bible" of psychiatry because it's the criteria mental health professionals use to diagnose their patients.
It is also used by insurance companies, schools and other agencies responsible for covering or creating special provisions for individuals with developmental or mental disorders.
Whether someone receives the death penalty or a lesser sentence can rise or fall depending on criteria for a mental health disorder as defined in the DSM.
Autism diagnoses will see significant changes in how patients are labeled.
Under the current manual, called the DSM-IV, children who meet the criteria for having autism are diagnosed with and told they have autistic disorder (also known as 'classic' autism) or Asperger's Syndrome or PDD-NOS, which stands for "Pervasive Developmental Disorder - Not Otherwise Specified."
In the new "DSM-5" manual, "the criteria will incorporate several diagnoses from DSM-IV including autistic disorder, Asperger's disorder, childhood disintegrative disorder and pervasive developmental disorder (not otherwise specified) into the diagnosis of autism spectrum disorder for DSM-5 to help more accurately and consistently diagnose children with autism," according to an APA statement Saturday.
When the new guidebook goes into effect in May, a child who has symptoms of Asperger's Syndrome, (problems with social interaction and unusual interests or behaviors but less likely to have problems with language or intellectual ability), will no longer be told he has Asperger's but rather "autism spectrum disorder (ASD)." The same goes for a child meeting the criteria for PDD-NOS or classic autism.
"I'm feeling quite good about the series of recommendations that were made in that area. It will help us diagnose these children in a more consistent way," said Dr. David J. Kupfer, who chairs the DSM-5 Task Force.
New research has led experts to have a better hand on social and communicative disorders as well as repetitive behaviors, he said.
Over the past few years, the APA has posted possible revisions of criteria, inviting comments from the other researchers and the public.
But these incremental revisions raised concerns among some researchers and advocacy groups who feared the new criteria would result in many children losing their autism diagnosis and much-needed services.
For example, in March, a study presented by Yale autism expert Dr. Fred Volkmar suggested only 60% of those meeting current criteria for autism would still be diagnosed with the disorder under the proposed criteria.
A recent, larger study found 9% of people might lose services, according to Autism Speaks, a research and advocacy group for people with autism.
Geraldine Dawson, chief science officer for Autism Speaks, said she was worried some people would be excluded by the new definitions and not receive the services they need.
"The concern is we really don't know yet how these changes are going to affect people in real world settings," she said.
Kupfer agrees that some children might fall off the autism spectrum, but he believes maybe 5% to 10% of patients will no longer meet the criteria for autism. He says he welcomes experts and advocacy groups to be vigilant and notify the APA if many more children lose their diagnoses.
But Dr. Bryan King says it's too early to say if children will be excluded.
King has been working on revising the autism diagnosis criteria since 2007 and also treats children with autism and other developmental disorders as the director of the Seattle Children's Autism Center.
He believes the new diagnostic criteria could be more inclusive and lead to more children being diagnosed with ASD. King says there are at least three big changes that could potentially open up the door for more (not less) children being diagnosed with autism:
1. A patient's history.
If, for instance, a teenager shows social impairments and sensory sensitivities (criteria for autism), but at the time of evaluation no longer lines up toys and is preoccupied with spinning wheels (other signs of autism), this history of repetitive behavior could be included to make an autism diagnosis. That's not possible under DSM-IV criteria.
2. Softening the criteria of the age of onset of symptoms.
Under the current guidelines for diagnosing a child with autism, symptoms have to occur before age 3. However, in some children, the impairment from autism may not be seen until a later age, particularly in people on the higher functioning end of the autism spectrum. The new criteria allow for older children to meet diagnostic criteria for autism.
3. Range of severity of symptoms.
Under the current DSM, in order to be diagnosed with autism, a child had to meet a certain amount of criteria at a certain level of severity.
"We offer up a range of severity of deficit that goes from abnormal social approach and failure of normal back-and-forth conversation all the way through complete lack of social communication. Everything in between is left to the clinician to be able to identify and work with," King says.
In the DSM-5, clinicians will not only have the criteria to refer to, they will be given actual examples of how children display these diagnostic criteria.
Dr. Max Wiznitzer, a pediatric neurologist and autism expert from Rainbow Babies and Children's Hospital in Cleveland, Ohio, says providing examples is one of the key changes in the DSM-5.
Explaining the criteria and providing examples will help minimize any potential misinterpretation and misdiagnosis, according to Wiznitzer.
"Part of the problem we've had with the application of DSM-IV diagnostic criteria is that people don't understand the underpinning of each of the diagnostic criteria and interpret them in a superficial manner."
This can lead to children incorrectly being diagnosed with autism as opposed to ADHD or other social or behavioral disorders.
Wiznitzer was not part of the group tasked with reviewing and revising the autism criteria. He believes that by better applying the new autism criteria, it could lead do some people not getting the ASD label in the first place, but those who already have autism will not lose their diagnosis.
Going forward in his practice, King says he will use the new criteria, but he's not going to retrospectively rediagnose patients. So in his practice, nobody will lose their autism diagnosis.
"We have people waiting months for an autism diagnosis," King says. "There's no way and no place for clogging the diagnostic wait lists for people to get rediagnosed for administrative purposes."
He hopes the APA and other organizations with provide formal recommendations that provide instructions for clinicians to only re-evaluate a patient diagnosed with an autism spectrum disorder under the current definition, if there's a clinical reason to so.
According to a statement from the APA, the new manual will include approximately the same number of disorders as were included in DSM-IV.
"This goes against the trend from other areas of medicine that increase the number of diagnoses annually," Kupfer said in the statement.
In addition, the next manual will see some more changes. They include:
-- Combining substance abuse and substance dependence into one overarching category called "Substance use disorder."
Kupfer says this makes sense because it allows experts to more easily diagnose some with an alcohol and/or drug problem by looking at a continuum of severity. He says this may also lead to earlier diagnoses, which might allow for appropriate interventions to be applied more easily.
"Previous substance abuse criteria required only one symptom while the DSM-5's mild substance use disorder requires two to three symptoms," the APA said in a statement.
-- Hoarding will now be in a category of its own, which is new.
It previously was considered a part of OCD. Kupfer says the change is based on extensive research that has been going for the past 15 to 20 years.
"It's something that we need to deal with because it really has highly harmful effects and a credible occurrence," he said.
-- Post-traumatic stress disorder (PTSD) will be included in a new chapter in DSM-5 on Trauma- and Stressor-Related Disorders, according to the APA. There will now be four distinct diagnostic clusters instead of three. The new diagnostic criteria will be more sensitive for children and adolescents to have PTSD. Kupfer says this shows a recognition that this, as with other disorders can develop much earlier than previously thought.
The last revision of the DSM was released in 1994, but experts started laying the groundwork for its revision five years later.
In 2007, the DSM task force and working groups were charged with reviewing the most recent research in the various areas of psychiatry.
The review and approval of the latest criteria is the final step in the process of updating this manual.
Between now and the end of the year, the DSM-5 will undergo a final editing process and then head to the printer. It will be officially released at the APA's regularly scheduled annual meeting in San Francisco in May.
CNN's Elizabeth Cohen and Jennifer Bixler contributed to this report.