There is emerging evidence for clinical and biological links between autism/pervasive developmental disorder (PDD) and schizophrenia, with particular attention to childhood-onset schizophrenia (COS). Autism
is a brain development disorder characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. PDD is a broader category that subsumes autism. Symptoms of PDD may include communication problems such as:
♣ Difficulty using and understanding language
♣ Difficulty relating to people, objects, and events; for example, lack of eye contact or pointing behavior
♣ Unusual play with toys and other objects
♣ Difficulty with changes in routine or familiar surroundings
♣ Repetitive body movements or behavior patterns
By contrast, a person diagnosed with schizophrenia may suffer from:
♣ Auditory hallucinations
♣ Delusions
♣ Disorganized and unusual thinking and speech
Childhood-onset schizophrenia is defined as onset of psychosis before 13 years and is a rare and severe form of schizophrenia. Onset is usually after age 7 years, and prognosis is poor.
The authors took clinical, demographic, and brain developmental data from the National Institute of Mental Health (and other) COS studies and reviewed family, imaging, and genetic data from studies of autism, PDD, and schizophrenia. In the two large studies that have examined these phenomena systematically, COS is preceded by and comorbid with PDD in 30% to 50% of cases. Other studies of children with early-onset schizophrenia have found evidence of pre-existing or co-existing developmental abnormalities primarily for communication, motor abnormalities, and/or social relatedness. For example, an early article from the UCLA COS study found that 39% of a sample of 33 patients had symptoms of autism years before onset of schizophrenia.
Epidemiological and family studies also find association between the disorders. In the current NIMH study to date, 263 family members were evaluated. Evidence from this study shows that the average 
Autism Screening Questionnaire score was higher among unaffected sibling of children with comorbid PDD/COS than among unaffected siblings of COS patients without PDD, as consistent with previous articles, implying that PDD symptoms are heritable and may serve as trait markers even in unaffected individuals.
Another interesting finding is that both disorders show evidence of accelerated trajectories of anatomic brain development at ages near disorder onset. Most researchers agree increased head size/total brain volume seen in the first 3 years of age is a marker for autism. This brain overgrowth that precedes or coincides with the appearance of signs and symptoms of autism suggests that it may be a fundamental aspect of the pathological process. In COS, there is exaggeration of the brain maturation processes of childhood and early adolescence.
Lastly, a growing number of risk genes and rare small chromosomal variants (microdeletions or duplications) are shared by schizophrenia and autism.
COMMENT:
Despite the fact that symptoms associated with PDD (which includes autism) are not like those associated with COS, there are new data to indicate that, autism and schizophrenia are more likely to be seen in the same patients and families: Large epidemiological and patient-population data show familial schizophrenia-like psychosis to be a risk factor for (narrowly defined) autism.
♣ Why are the links between these illnesses not seen by the treating clinician?
♣ One reason is that the children who typically have these conditions present with a variety of symptoms which dilutes the effects in smaller samples.
♣ The other reason is that autism and schizophrenia are mutually exclusive under the current diagnostic hierarchy. This means that if a person develops autism as a young child, they may be unlikely to receive a diagnosis of schizophrenia later on, even if new symptoms emerge.
♣ To address these issues, the training of psychiatrists who treat adults with this spectrum of disorders needs to include the diagnosis of adults with autism and autism spectrum/PDD to discriminate the milder forms of autism spectrum and schizophrenia spectrum disorder for future family studies.
♣ Lastly, a meticulous study of genetic and syndromal heterogeneity is needed to form a foundation for future clinical neuroscience.
To read this study in its entirety, go to J Am Acad Child Acolesc Psychiatry, 48:1, January 2009, pp. 10-18.
-–Cynthia Haggard is a medical writer who lives in Washington DC. She owns her own business, Clarifying Concepts, which provides technical writing, writing for the public, and regulatory affairs services. To see more, please go to clarifyingconcepts. (c) 2009 All rights reserved.
Hello,
I have just read this article and I think I understand what you are suggesting.
I have a child of six who has been diagnosed with Autistic Spectrum Disorder. His symptoms are very mild and are mainly around problems with authority and social awareness.
However he has always had another problem since about the age of three (not diagnosed) we first noticed it. This is that he gets noises in his head. When he was younger he said he gets constant shouting (very loud) in his head (often lasts all day until he goes to sleep … does not always sleep well at night … and can have the voices again as soon as he wakes up) … three years later, we have discovered that these are voices in his head telling him to do bad things like hurting people … but he explains …” I do not want to punch you Mummy because you are so kind” – he explains that he does not want to do them, but finds it difficult to block them out. (We have never allowed him to watch anything other than things like CBeebies and Disney cartoons – because he takes everything so literally).
Our friends find it difficult to understand he has a problem as it is not apparent to them because he is so kind hearted only those close to us are starting to understand and see the differences. Had it not been for the school he goes to we would never have got him diagnosed.
As parents this greatly concerns us, so if you have any further information on this or have a contact in the UK then this would be appreciated.
Thank you for posting this.
Kind regards,
Toby
Dear Toby,
I am so sorry to hear about your son. Unfortunately, I do not have a contact in the UK, but my advice to you would be to take your son to 2 or 3 (or as many as you need to see) clinical neuroscientists ASAP to get a diagnosis of what is going on with these voices he’s hearing. I would advise you to take the article I cited and ask the doctor that there seems to be evidence of a link between autism & schizophrenia. I hope this helps. I apologize for my tardy reply, I was at a conference last week. Best of luck, Cynthia.