Shift happens: family background influences clinical
variability in genetic neurodevelopmental disorders (May 2015)
How to better predict a child’s intellectual and behavioral progression

Traditionally, neurodevelopmental features of genetic syndromes, such as intellectual disability, social abilities, and autism, have been described as being simply “present” or “absent.” Describing these features in such a black-or-white fashion suggests that a child has an all-or-none chance to develop features such as intellectual disability or autism.

However, in reality, these features occur on a scale, appearing in varying degrees from individual to individual. Out-dated methods of trying to predict whether a child will experience neurodevelopmental problems have caused many challenges and frustrations for medical professionals and, more importantly, for families. This article calls for a new, more accurate way to help families predict their child’s intellectual and behavioral development. The reason for this change is because classic descriptions of “autism” or “bipolar disorder” are descriptions of a behavioral diagnosis. We often see that children with genetic diagnoses have a mixed-bag of different behavioral diagnoses, all related to differences in brain function.


Recent studies have shown that IQ, behavior, and other social and cognitive (learning) features can be predicted for a child with a genetic change (like 16p11.2 deletion) based on his/her family members’ abilities, or family background. For example, one study demonstrated the relationship between parental IQ and child IQ. If two parents have higher-than-average IQs, their child with a 16p11.2 deletion will most likely have an IQ that is lower than either parent (shifted downwards), but not necessarily low enough to fall within the intellectual disability range. Similarly, the IQ of a child with a 16p11.2 deletion whose parents have slightly lower than average IQs is also shifted downwards, but may be more likely fall within the intellectual disability range.

In the following graphs the orange curve represents the IQ distribution of individuals with 16p11.2 deletions. The blue curve represents the IQ distribution of unaffected parents (and siblings?). The orange arrow demonstrates the shift of IQ related to the genetic diagnosis.


 

These unaffected parents have a “low-normal” IQ. The  IQ of their child with the 16p11.2 deletion is low-normal in comparison to other children with 16p11.2 deletion and has also shifted to be lower than the partents’ IQ.

 

These unaffected parents have a “high-normal” IQ. The IQ of their child with the 16p11.2 deletion is high-normal in comparison to other children with 16p11.2 deletion, but has shifted to be lower than the patents’ IQ.


In other words, the level of the parents’ intellectual and behavioral functioning is “shifted” for their child with the genetic change; and this can help predict where the child’s level of functioning will be. Findings such as these play an important role in how families should be counseled about their child’s chances of being diagnosed with autism or intellectual disability.

The goal is to use this newly recognized IQ “shift” to better understand a child’s neurodevelopmental and psychology risks. With better understanding and further research, medical professionals and families can begin to integrate proactive intervention for children at risk for intellectual disability and autism, as opposed to the current approach of “watchful waiting”.