Hoarding Linked to BDNF Gene in OCD

In two previous posts on hoarding, I have reviewed some the pathway and profile of animal hoarding as well as the common mental health problems found with hoarding.

Today I will review a study that provides some insight into potential genetic contributions to hoarding behavior.  Of interest, this genetic link also appears to carry some increased risk for obesity.

Timpano from the University of Miama along with colleagues at Florida State University and the National Institute of Mental Health Intramural programs have recently published a study of 301 subjects with obsessive compulsive disorder (OCD).

In previous posts it was noted that hoarding can occur in the context of OCD but that not all hoarders will meet criteria for OCD.  In the Timpano et al study, subjects started with a diagnosis of OCD and then were grouped into those with hoarding and those without hoarding behaviors.

The hoarding classification status was assigned based upon the subject response to two items found on the Yale Brown Obsessive Compulsive Scale (YBOCS).  One item queried about tending to save objects and second item queried about difficulty discarding objects.  Hoarding subjects were required to endorse both items.

The research team then looked at the subjects and the brain-derived neurotrophic factor (BDNF) status.  BDNF has been a genetic region of interest in a variety of clinical neuroscience conditions including schizophrenia, anxiety and aggression.  Additionally it appears to be involved in memory function and variants of BDNF have been linked to higher rates of obesity.

BDNF appears to serve a role as a central neurological system plasticity factor and modulates both serotonin and glutamatergic neurotransmitter systems.  The BDNF gene codes for a protein that can vary in an region in status of two amino acids valine and methionine.  At this regions, individuals can be assigned one of three genetic types: Val/val, val/met or met/met.

The Timpano et al team found the following key findings:

• About 25% of those with OCD met criteria for being hoarders

• The BDNF val/val genotype was found in 77% of the hoarding group versus only 60% of the non-hoarding OCD group
• The BDNF val/val genotype correlated with increased hoarding symptom severity and BMI
• 45% of the hoarding group met criteria for obesity (BMI >30) versus only 21% of the OCD only group

The authors note that there are animal models of hoarding where hoarding behaviors have been linked to dysregulation of feeding behaviors.  When humans begin to hoard objects, there may also be a overlapping drive to hoard (and consume) food.  The authors note there may be a complex gene mechanism whereby individuals display hoarding, increased body weight and psychopathology as evidence of a "thrifty gene" strategy that may have survival and evolutionary manifestations.

It would be informative to examine the BDNF gene status of hoarders without a diagnosis of OCD.  The authors note that interaction between BDNF and serotonergic function may partially explain some other the BDNF-hoarding-obesity triad.

There role of serotonin in OCD has received significant research attention. In the next post, I will look at the potential for selective serotonergic antidepressants pharmocotherapy in the treatment of hoarding behaviors.

The molecular model of BDNF above is in the public domain from a Creative Commons Attribution-ShareAlike 3.0 file (Wikepedia) authored by Microswitch.

Timpano, K., Schmidt, N., Wheaton, M., Wendland, J., & Murphy, D. (2011). Consideration of the BDNF gene in relation to two phenotypes: hoarding and obesity. Journal of Abnormal Psychology DOI: 10.1037/a0024159