“New genetic evidence suggests a continuum among neurodevelopmental and psychiatric disorders”

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A broad spectrum of developmental and psychiatric disorders, ranging from autism and intellectual disability to schizophrenia, should be conceptualized as different manifestations of a common underlying denominator, “developmental brain dysfunction,” rather than completely independent conditions with distinct causes, new research suggests.

• Developmental disorders (such as autism and intellectual disability) and psychiatric disorders (such as schizophrenia and bipolar disorder), while considered clinically distinct, actually share many of the same underlying genetic causes. This is an example of “variable expressivity:” the same genetic variant results in different clinical signs and symptoms in different individuals.
• When quantitative measures of neuropsychological and neurobehavioral traits are studied instead of categorical diagnoses (which are either present or absent) and individuals are compared to their unaffected family members, it is possible to more accurately demonstrate the impact of genetic variants.

“Recent genetic studies conducted in thousands of individuals have shown that identical genetic mutations are shared among neurodevelopmental disorders that are thought to be clinically distinct. What we have seen over the past few years is that genetic mutations that were initially found in individuals with one disorder, such as intellectual disability or autism, are then identified in people with an apparently different condition like schizophrenia, epilepsy, or bipolar disorder.”

“It turns out that the genes don’t respect our diagnostic classification boundaries, but that really isn’t surprising given the overlapping symptoms and frequent co-existence of neurodevelopmental disorders,”

“We believe this study supports use of the term ‘developmental brain dysfunction’ or DBD, which would encompass the broad spectrum of neurodevelopmental and neuropsychiatric disorders…Additionally, it is clear that diagnostic tools such as whole genome analysis for both children and their families are essential when diagnosing and treating these disorders in order to ensure the most personalized treatment.”

“One implication of this concept is that studies designed to investigate the causes and mechanisms of developmental brain dysfunction should focus on measurement of quantifiable neuropsychological and neurobehavioral traits across groups of individuals with different clinical diagnoses. Another is that whenever possible, individuals with a particular genetic variant or other risk factor should be compared to their unaffected family members, not just to population norms.”

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