We have previously described a subtype of panic disorder (PD) that we termed ‘bladder syndrome’, characterized by urological and bladder symptoms (and possibly interstitial cystitis) in the patients and/or their family members and confirmed the validity of this subset in family linkage and association analysis. In this study, we determine (a) whether 20 single-nucleotide polymorphisms (SNPs) reported in the literature can be replicated in a new PD dataset and (b) whether dividing the sample into those with and without the ‘bladder syndrome’ can help to resolve the genetic heterogeneity within this new sample.
We selected 20 putative associated SNPs from the literature, taken from studies published since 2004. We tested these SNPs for association in a sample of 351 PD patients and 552 controls, and then divided them into subgroups of 92 patients from bladder families and 259 from nonbladder families.
(a) When analyzed in all PD patients, none of the 20 SNPs appeared to be replicated (except for SLC6A4 from our previous study, but in a sample that overlaps substantially with that in our previous report). (b) However, some intriguing findings emerged when we separated bladder from nonbladder families: SLC6A4, reported by us previously, yielded stronger evidence than before (P=0.0018) when examined only in nonbladder families, and in contrast, is not statistically significant in bladder families. Two other markers yielded nominally significant results in bladder families – rs5751876 in ADORA2A (P=0.046) and rs12579350 in TMEM16B (P=0.035) – but were not significant in nonbladder families. (c) Two markers had noticeably lower P-values when we differentiated the women and analyzed them separately – rs12579350 in TMEM16B (P-value decreased from 0.035, as above, to 0.00055) and a different SNP in ADORA2A, rs4822492 (P-value decreases from 0.07 to 0.028).
Our results indicate that most of the 20 reported associations do not hold up when PD is analyzed as one group. However, our findings provide further evidence that PD with bladder symptoms may be genetically different from PD without bladder. We suggest that it is worth pursuing SLC6A4 in nonbladder PD, and ADORA2A and TMEM16B in bladder PD. Also, the possibility of a male–female difference in PD is worth pursuing. We also briefly discuss issues of replication and multiple tests.
aDepartment of Psychiatry, College of Physicians and Surgeons
bDepartment of Biostatistics, Division of Statistical Genetics, Mailman School of Public Health
cDepartment of Epidemiology, Mailman School of Public Health, Columbia University
dDivision of Epidemiology
eDivision of Clinical Therapeutics, New York State Psychiatric Institute, New York, New York
fDepartment of Psychiatry and Institute for Human Genetics, University of California, San Francisco, California, USA
Correspondence to Susan E. Hodge, DSc, Battelle Center for Mathematical Medicine, Nationwide Children’s Hospital, Research Building 3, 575 Children’s Crossroad, Columbus, OH 43215, USA Tel: +1 614 355 6673; fax: +1 614 355 5898; e-mail: Susan.Hodge@nationwidechildrens.org
Received October 4, 2011
Accepted February 16, 2012