BOSTON-The Sensory Processing Disorder Foundation symposium held in Boston earlier this month highlighted all kinds of research that are going on with SPD. Most impressive was the fact that it is being done all across the country. Most disheartening is that SPD is still hard to tease out of a sub-role in other psychiatric diagnoses. But when pressed as to whether sensory defensiveness really is a differential diagnosis, Harvard Medical School professor and genetics researcher David Pauls, PhD, admitted that he thinks it is-in extreme cases.

"Research shows there are people with pretty extreme behaviors with no other psychiatric diagnoses, and we don't know at this point what is causing them," Pauls said. "There is a significant underlying biological deficit. They would benefit from intervention."

Pauls is head of Massachusetts General Hospital's psychiatric and neurodevelopmental genetics unit, set up in 2001 under the hospital's center for human genetic research and department of psychiatry. He is the lead researcher in a continuing, two-pronged study, a Genetic Linkage Study of Tourette Syndrome, and a Family Linkage Study of TS, ADHD and OCD. Sensory issues were part of the studies.

"It's quite clear that there won't be a single gene connected with this condition," he told his audience of practitioners and educators. "[But] there are probably some underlying genetic factors that are contributing to these behaviors."

The factors that indicate this have been consistent in several studies done recently using parent-interview measurements across related and non-related groups of children. One showed inheritability to be possibly as high as 40 percent.

Pauls recommends further "association" studies that are family-based to collect more information on this. Though in family studies you cannot distinguish between genetic and non-genetic factors, by looking at ­distribution of DNA in child and parents, you can see which genes did and did not get transmitted. If you then look at a series of kids with sensory problems, you can compare how many have had the same things transmitted and then compare what the genetic profile is to the sensory behavior. This is cheaper, he said, than doing case/control studies that require huge numbers of subjects and can be cost-prohibitive.

The important task, in order to establish sensory defensiveness as a differential diagnosis, is to look for it in people who have no other psychopathology. That has been difficult to prove. It is often associated with Tourette syndrome, autism spectrum disorders, ADHD and OCD. But Pauls says that there are high-end cases of over-responsiveness that stand alone, without any co-morbidities.

Lucy Miller, founder and executive director of the SPD Foundation, has been working to get SPD recognized as an independently diagnosable disorder for the past 30 years. She and her team are in the midst of trying to get sensory processing disorder listed as a diagnosis in the upcoming fifth edition of the Diagnostic and Statistical Manual of Mental Disorders that outlines mental health and behavioral disorders. Its inclusion would put SPD treatment on the map, so to speak, in terms of reimbursement and research funding.

The final application has to be filed by January 2010. Otherwise, the door closes until the next edition of the manual is published in 2025. Miller has said the foundation needs half a million dollars to finish the research it needs to do in order to make that application. A separate funding arm working on the project is the Spiral Foundation (spiralfoundation.com).

The Mass General/Harvard family genetics study looked at 110 families with 318 first-degree relatives who participated in full psychiatric interviews and offered ­symptom-specific information. Many families had several of the diagnoses. Researchers used Miller's Sensory Over-responsiveness Scale: Inventory for Sensory Defensiveness. It includes eight sensory domains.

The sensory factors definitely were co-related among relatives, with a SORS score of .14, a significant finding. On another scale, the Sensory Profile, the correlation was even higher: .17.

"There is evidence that [sensory defensiveness] is familial," Pauls said. It's not completely genetic, or scores would be more like .5.

Pauls even noted that animal studies at the Harlow Primate Center at the University of Wisconsin have seen sensory defensiveness in Rhesus monkeys.

As to his own work, the more co-morbidities study subjects had, of course, the more different they were on sensory measures. "Sensory response to stimulus is under some sort of genetic influence," he concluded, and in the Harlow studies, the more closely related the monkeys were, the more the problem showed up. "Habituation is not related," Pauls noted. "Other things are moderating habituation."

What this means clinically is that non-genetic and non-pharmacological intervention should work on sensory defensiveness.

OTs have long known that it does.

For more information on Pauls' studies, go to http://www.ts-adhd-ocd.org/team.html

E.J. Brown is editor of ADVANCE.