Caring for our children's future
Date: April, 2015
Investigators explored whether the diversity of clinical features across patients with autism reflects heterogeneous sources of genetic risk. In search for a "purer" autism i.e., a more genetically homogenous, group of patients, making it easier to find autism-related genes, researchers selected a group of patients with similar clinical features. Scientists used data from the Simons Simplex Collection, which includes 2576 autism families, the largest such cohort collected to date.
In this sample, there were 11 subgroups of patients with similar diagnostic, IQ and symptom profiles identified. Researchers then analysed the data for each subgroup in an attempt to discover common genetic variants that signal risk for autism spectrum disorder.
Their results did not identify any genome-wide significant associations in the overall sample or in the phenotypic subgroups. This means that the extreme clinical variability observed among patients with autism spectrum disorder does not closely reflect common genetic variation. "This study did not provide good evidence that selecting patients with similar symptoms results in a greater ability to find autism genes," said Dr. John Krystal, Editor of Biological Psychiatry. "This might suggest that some of the clinical variability in autism arises from causes other than genetic vulnerability, such as responses to the environment."
It is important to note that these results are in alignment with the recent major change to autism's diagnostic classification in the Diagnostic and Statistical Manual of Mental Disorders. In its 5th revision, several separate disorders, which included autism and Asperger's disorder, were grouped into a single category termed autism spectrum disorder. That decision was based on growing evidence that the previously-distinct disorders actually reflected a continuum of severity of the same condition.
Chaste, P. et al. (2015). A genome-wide association study of autism using the Simons Simplex Collection: Does reducing phenotypic heterogeneity in autism increase genetic homogeneity? Biological Psychiatry, 77, DOI: 10.1016/j.biopsych.2014.09.017
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