Genetic correlates in trichotillomania--A case-control association study in the South African Caucasian population.
BACKGROUND
Trichotillomania (TTM), a prevalent and disabling psychiatric disorder characterized by repetitive hair-pulling, is presently classified as an impulse control disorder (ICD). Some have argued, however, that TTM is an obsessive-compulsive spectrum disorder (OCSD). There is some evidence that both disorders (OCD and TTM) are mediated by serotonergic (5-HT) and dopaminergic pathways.


METHODS
The aim of the present investigation was to assess the role of candidate genes encoding components within the 5-HT and dopaminergic neurotransmitter pathways in mediating TTM. South African Caucasian TTM subjects (n=39), OCD (n=250) and control subjects (n=152) were genotyped for variants in 5-HT and dopaminergic candidate genes.


RESULTS
Both genotypic and allelic distributions of the 5-HT receptor 2A (5-HT2A) T102C variant were found to be significantly different between the TTM and control subjects (p=0.028 and p=0.024, respectively), and a trend towards significance was noted between the TTM and OCD subjects (p=0.084 and p=0.080 for genotype and allele analyses, respectively), with the T102T-genotype found to confer susceptibility to the development of TTM.


CONCLUSIONS
This investigation provides preliminary evidence for the involvement of 5-HT2A in the molecular aetiology of TTM and supports the need for further replication in a larger dataset. The present data are consistent with previous findings that 5-HT2A plays a role in mediating impulse dyscontrol.
Hemmings
Sîan M J
SM
MRC/US Centre for Molecular and Cellular Biology, University of Stellenbosch, Tygerberg, South Africa. smjh@sun.ac.za
Kinnear
Craig J
CJ
Lochner
Christine
C
Seedat
Soraya
S
Corfield
Valerie A
VA
Moolman-Smook
Johanna C
JC
Stein
Dan J
DJ
D000483:Alleles; D002135:Calcium-Binding Proteins / Q000235:genetics; D016022:Case-Control Studies; D004298:Dopamine / Q000378:metabolism; D005838:Genotype; D006023:Glycoproteins / Q000235:genetics; D006801:Humans; D009434:Neural Pathways / Q000502:physiology; D009771:Obsessive-Compulsive Disorder / Q000378:metabolism; D011110:Polymorphism, Genetic / Q000235:genetics; D000071999:S100 Calcium-Binding Protein A4; D012701:Serotonin / Q000378:metabolism; D013019:South Africa / Q000453:epidemiology; D014256:Trichotillomania / Q000235:genetics* / Q000378:metabolism; D044465:White People / Q000706:statistics & numerical data*
D002135:Calcium-Binding Proteins; D006023:Glycoproteins; D000071999:S100 Calcium-Binding Protein A4; C021240:tissue-factor-pathway inhibitor 2; C077591:S100A4 protein, human; D012701:Serotonin; D004298:Dopamine