Academic Biography

Dr. Paul Arnold is an investigator with the Genetics and Genomic Biology Program, Hospital for Sick Children and staff psychiatrist at The Hospital for Sick Children and Centre for Addiction and Mental Health.   His research focus is on understanding the genetic determinants of early onset Obsessive Compulsive Disorder (OCD).

What is Obsessive Compulsive Disorder?

OCD is a chronic anxiety disorder most commonly characterized by distressing, intrusive thoughts (obsessions), and ritualized tasks (compulsions) performed in an attempt to neutralize the obsessions.  OCD affects up to 3% of people in their lifetime, with onset typically occurring in childhood or adolescence. 

Project Summary

Dr. Arnold and his team are conducting a genetic study focusing on early onset (diagnosis prior to 15 years of age) OCD.  Building on their earlier work, Dr. Arnold’s team is thoroughly testing a substantial group of participants recruited by researchers at the University of Toronto, the University of Michigan at Ann Arbor, Wayne State University in Michigan and the University of Florida in Gainesville.  To our knowledge, this is the largest study in the world involving participants with OCD. With this grant, he is investigating many more potential genetic variations in glutamate transporters associated with OCD. 

Biological Background and Rationale

The group of biological structures (the candidate biological system) in this study is the family of glutamate transporters and receptors located on the surface of neurons, and the set of genes essential for their formation.  Glutamate transporters are large molecules that pump glutamate, a neurotransmitter, between cells at a regulated rate. Glutamate receptors are specialized structures to which glutamate binds, leading to a cascade of events within the cell resulting in changes of neuronal function. Proper functioning of both glutamate receptors and transporters is necessary for healthy brain function.  Irregular function of glutamate transporters or receptors has been linked to schizophrenia, mood disorders, and other anxiety disorders.  Irregular function of glutamate transporters may arise from several causes, such as abnormal structure of the transporter due to genetic variation, or from injury. 

Dr. Arnold has chosen to focus on early onset OCD, which is more likely due to genetic causes compared with adult onset OCD, to investigate whether OCD is associated with irregular function of glutamate transporters and receptors, and whether this irregular function has a genetic cause.  He has ample support for his investigation of the glutamate system: earlier research conducted by his group has found a positive link association between OCD and genetic variation in two glutamate system genes.  Research conducted by other groups, including drug and animal model studies, also supports an association between glutamate system genes and OCD.

Outcome

As the research continues, this experimental information will be checked against known diagnostic methods for OCD.  Any associations between genetic variation in glutamate transporters or receptors and occurrences of OCD will go on to be statistically analyzed to determine whether more diagnostic information can be extracted from the initial results. 

This research will provide us with a better understanding of the biological causes and the nature of OCD, which may in turn lead to more effective medical treatment of this disorder.