Whole-genome association analysis of treatment response in obsessive-compulsive disorder

Up to 30% of patients with obsessive-compulsive disorder (OCD) exhibit an inadequate response to serotonin reuptake inhibitors (SRIs). To date, genetic predictors of OCD treatment response have not been systematically investigated using genome-wide association study (GWAS). To identify specific genetic variations potentially influencing SRI response, we conducted a GWAS study in 804 OCD patients with information on SRI response. SRI response was classified as 'response' (n=514) or 'non-response' (n=290), based on self-report. We used the more powerful Quasi-Likelihood Score Test (the MQLS test) to conduct a genome-wide association test correcting for relatedness, and then used an adjusted logistic model to evaluate the effect size of the variants in probands. The top single-nucleotide polymorphism (SNP) was rs17162912 (P=1.76 × 10(-8)), which is near the DISP1 gene on 1q41-q42, a microdeletion region implicated in neurological development. The other six SNPs showing suggestive evidence of association (P<10(-5)) were rs9303380, rs12437601, rs16988159, rs7676822, rs1911877 and rs723815. Among them, two SNPs in strong linkage disequilibrium, rs7676822 and rs1911877, located near the PCDH10 gene, gave P-values of 2.86 × 10(-6) and 8.41 × 10(-6), respectively. The other 35 variations with signals of potential significance (P<10(-4)) involve multiple genes expressed in the brain, including GRIN2B, PCDH10 and GPC6. Our enrichment analysis indicated suggestive roles of genes in the glutamatergic neurotransmission system (false discovery rate (FDR)=0.0097) and the serotonergic system (FDR=0.0213). Although the results presented may provide new insights into genetic mechanisms underlying treatment response in OCD, studies with larger sample sizes and detailed information on drug dosage and treatment duration are needed.

Dependent personality, separation anxiety disorder and other anxiety disorders in OCD

BACKGROUND

The purpose of this study was to investigate whether dependent personality and/or general personality dimensions might explain the strong relationships between separation anxiety disorder (Sep-AD) and three other anxiety disorders (agoraphobia, panic disorder and social anxiety disorder) in individuals with obsessive compulsive disorder (OCD).

METHODS

Using data from 509 adult participants collected during the OCD Collaborative Genetic Study, we used logistic regression models to evaluate the relationships between Sep-AD, dependent personality score, general personality dimensions and three additional anxiety disorders.

RESULTS

The dependent personality score was strongly associated with Sep-AD and the other anxiety disorders in models adjusted for age at interview, age at onset of OC symptoms and worst ever OCD severity score. Several general personality dimensions, especially neuroticism, extraversion and conscientiousness, were also related to Sep-AD and the other anxiety disorders. Sep-AD was not independently related to these anxiety disorders, in multivariate models including general personality and dependent personality disorder scores.

CONCLUSIONS

The results suggest that Sep-AD in childhood and these other anxiety disorders in adulthood are consequences of dependent personality disorder (for agoraphobia and panic disorder) or introversion (for social phobia). It is unknown whether these results would be similar in a non-OCD sample.

Meta-analysis of association between obsessive-compulsive disorder and the 3' region of neuronal glutamate transporter gene SLC1A1

The neuronal glutamate transporter gene SLC1A1 is a candidate gene for obsessive-compulsive disorder (OCD) based on linkage studies and convergent evidence implicating glutamate in OCD etiology. The 3' end of SLC1A1 is the only genomic region with consistently demonstrated OCD association, especially when analyzing male-only probands. However, specific allele associations have not been consistently replicated, and recent OCD genome-wide association and meta-analysis studies have not incorporated all previously associated SLC1A1 SNPs. To clarify the nature of association between SLC1A1 and OCD, pooled analysis was performed on all available relevant raw study data, comprising a final sample of 815 trios, 306 cases and 634 controls. This revealed weak association between OCD and one of nine tested SLC1A1 polymorphisms (rs301443; uncorrected P = 0.046; non-significant corrected P). Secondary analyses of male-affecteds only (N = 358 trios and 133 cases) demonstrated modest association between OCD and a different SNP (rs12682807; uncorrected P = 0.012; non-significant corrected P). Findings of this meta-analysis are consistent with the trend of previous candidate gene studies in psychiatry and do not clarify the putative role of SLC1A1 in OCD pathophysiology. Nonetheless, it may be important to further examine the potential associations demonstrated in this amalgamated sample, especially since the SNPs with modest associations were not included in the more highly powered recent GWAS or in a past meta-analysis including five SLC1A1 polymorphisms. This study underscores the need for much larger sample sizes in future genetic association studies and suggests that next-generation sequencing may be beneficial in examining the potential role of rare variants in OCD.

Homeobox genes in obsessive-compulsive disorder

BACKGROUND

Despite evidence that obsessive-compulsive disorder (OCD) is a familial neuropsychiatric condition, progress aimed at identifying genetic determinants of the disorder has been slow. The OCD Collaborative Genetics Study (OCGS) has identified several OCD susceptibility loci through linkage analysis.

METHODS

In this study we investigate two regions on chromosomes 15q and 1q by first refining the linkage region using additional short tandem repeat polymorphic (STRP) markers. We then performed association analysis on single nucleotide polymorphisms (SNP) genotyped (markers placed every 2-4 kb) in the linkage regions in the OCGS sample of 376 rigorously phenotyped affected families.

RESULTS

Three SNPs are most strongly associated with OCD: rs11854486 (P = 0.00005 [0.046 after adjustment for multiple tests]; genetic relative risk (GRR) = 11.1 homozygous and 1.6 heterozygous) and rs4625687 [P = 0.00007 (after adjustment = 0.06); GRR = 2.4] on 15q; and rs4387163 (P = 0.0002 (after adjustment = 0.08); GRR = 1.97) on 1q. The first SNP is adjacent to NANOGP8, the second SNP is in MEIS2, and the third is 150 kb between PBX1 and LMX1A.

CONCLUSIONS

All the genes implicated by association signals are homeobox genes and are intimately involved in neurodevelopment. PBX1 and MEIS2 exert their effects by the formation of a heterodimeric complex, which is involved in development of the striatum, a brain region involved in the pathophysiology of OCD. NANOGP8 is a retrogene of NANOG, a homeobox transcription factor known to be involved in regulation of neuronal development. These findings need replication; but support the hypothesis that genes involved in striatal development are implicated in the pathogenesis of OCD.

Is obsessive-compulsive disorder an anxiety disorder, and what, if any, are spectrum conditions? A family study perspective

BACKGROUND

Experts have proposed removing obsessive-compulsive disorder (OCD) from the anxiety disorders section and grouping it with putatively related conditions in DSM-5. The current study uses co-morbidity and familiality data to inform these issues.

METHOD

Case family data from the OCD Collaborative Genetics Study (382 OCD-affected probands and 974 of their first-degree relatives) were compared with control family data from the Johns Hopkins OCD Family Study (73 non-OCD-affected probands and 233 of their first-degree relatives).

RESULTS

Anxiety disorders (especially agoraphobia and generalized anxiety disorder), cluster C personality disorders (especially obsessive-compulsive and avoidant), tic disorders, somatoform disorders (hypochondriasis and body dysmorphic disorder), grooming disorders (especially trichotillomania and pathological skin picking) and mood disorders (especially unipolar depressive disorders) were more common in case than control probands; however, the prevalences of eating disorders (anorexia and bulimia nervosa), other impulse-control disorders (pathological gambling, pyromania, kleptomania) and substance dependence (alcohol or drug) did not differ between the groups. The same general pattern was evident in relatives of case versus control probands. Results in relatives did not differ markedly when adjusted for demographic variables and proband diagnosis of the same disorder, though the strength of associations was lower when adjusted for OCD in relatives. Nevertheless, several anxiety, depressive and putative OCD-related conditions remained significantly more common in case than control relatives when adjusting for all of these variables simultaneously.

CONCLUSIONS

On the basis of co-morbidity and familiality, OCD appears related both to anxiety disorders and to some conditions currently classified in other sections of DSM-IV.

A screen of SLC1A1 for OCD-related alleles

SLC1A1, which encodes the neuronal and epithelial glutamate transporter, is a promising candidate gene for obsessive-compulsive disorder (OCD). In this study, we conducted capillary electrophoresis single-strand conformation polymorphism (CE-SSCP) screen for all 12 identified exons, including all coding regions and approximately 50 bp of flanking introns of the human SLC1A1 in 378 OCD-affected individuals. Full sequencing was completed on samples that showed an aberrant SSCP tracing for identification of the underlying sequence variants. Our aim was to determine if there are differences in the frequencies of relatively common alleles, or rare functional alleles, in 378 OCD cases and 281 ethnically matched controls. We identified one nonsynonymous coding SNP (c.490A > G, T164A) and three synonymous coding SNP (c.81G > C, A27A; c.414A > G, T138T; c.1110T > C, T370T) in case samples. We found no statistical differences in genotype and allele frequencies of common cSNPs in SLC1A1 between the OCD cases and controls. The rare variant T164A was found only in one family. Further investigation of this variant is necessary to determine whether and how it is related to OCD. There was no other evidence of significant accumulation of deleterious coding mutations in SLC1A1 in the OCD cases.

A family-based association study of the glutamate transporter gene SLC1A1 in obsessive-compulsive disorder in 378 families

SLC1A encodes the neuronal and epithelial glutamate transporter and was previously tested as a candidate for obsessive-compulsive disorder (OCD) by several research groups. Recently, three independent research groups reported significant association findings between OCD and several genetic variants in SLC1A1. This study reports the results from a family-based association study, which examined the association between 13 single nucleotide polymorphisms (SNPs) within or in proximity to the SLC1A1 gene. Although we did not replicate association findings for those significant SNPs reported by previous studies, our study indicated a strong association signal with the SNP RS301443 (P-value = 0.000067; Bonferroni corrected P-value = 0.0167) under a dominant model, with an estimated odds ratio of 3.5 (confidence interval: 2.66-4.50). Further, we conducted single SNP analysis after stratifying the full data set by the gender status of affected in each family. The P-value for RS301443 in families with the male affected was 0.00027, and the P-value in families with female affected was 0.076. The fact that we identified a signal which was not previously reported by the other research groups may be due to differences in study designs and sample ascertainment. However, it is also possible that this significant SNP may be part of a regulator for SLC1A1, given that it is roughly 7.5 kb away from the boundary of the SLC1A1 gene. However, this potential finding needs to be validated biologically. Further functional studies in this region are planned by this research group.

Obsessive-compulsive disorder: subclassification based on co-morbidity

BACKGROUND

Obsessive-compulsive disorder (OCD) is probably an etiologically heterogeneous condition. Many patients manifest other psychiatric syndromes. This study investigated the relationship between OCD and co-morbid conditions to identify subtypes.

METHOD

Seven hundred and six individuals with OCD were assessed in the OCD Collaborative Genetics Study (OCGS). Multi-level latent class analysis was conducted based on the presence of eight co-morbid psychiatric conditions [generalized anxiety disorder (GAD), major depression, panic disorder (PD), separation anxiety disorder (SAD), tics, mania, somatization disorders (Som) and grooming disorders (GrD)]. The relationship of the derived classes to specific clinical characteristics was investigated.

RESULTS

Two and three classes of OCD syndromes emerge from the analyses. The two-class solution describes lesser and greater co-morbidity classes and the more descriptive three-class solution is characterized by: (1) an OCD simplex class, in which major depressive disorder (MDD) is the most frequent additional disorder; (2) an OCD co-morbid tic-related class, in which tics are prominent and affective syndromes are considerably rarer; and (3) an OCD co-morbid affective-related class in which PD and affective syndromes are highly represented. The OCD co-morbid tic-related class is predominantly male and characterized by high conscientiousness. The OCD co-morbid affective-related class is predominantly female, has a young age at onset, obsessive-compulsive personality disorder (OCPD) features, high scores on the 'taboo' factor of OCD symptoms, and low conscientiousness.

CONCLUSIONS

OCD can be classified into three classes based on co-morbidity. Membership within a class is differentially associated with other clinical characteristics. These classes, if replicated, should have important implications for research and clinical endeavors.

Sapap3 and pathological grooming in humans: Results from the OCD collaborative genetics study

SAP90/PSD95-associated protein (SAPAP) family proteins are post-synaptic density (PSD) components that interact with other proteins to form a key scaffolding complex at excitatory (glutamatergic) synapses. A recent study found that mice with a deletion of the Sapap3 gene groomed themselves excessively, exhibited increased anxiety-like behaviors, and had cortico-striatal synaptic defects, all of which were preventable with lentiviral-mediated expression of Sapap3 in the striatum; the behavioral abnormalities were also reversible with fluoxetine. In the current study, we sought to determine whether variation within the human Sapap3 gene was associated with grooming disorders (GDs: pathologic nail biting, pathologic skin picking, and/or trichotillomania) and/or obsessive-compulsive disorder (OCD) in 383 families thoroughly phenotyped for OCD genetic studies. We conducted family-based association analyses using the FBAT and GenAssoc statistical packages. Thirty-two percent of the 1,618 participants met criteria for a GD, and 65% met criteria for OCD. Four of six SNPs were nominally associated (P < 0.05) with at least one GD (genotypic relative risks: 1.6-3.3), and all three haplotypes were nominally associated with at least one GD (permuted P < 0.05). None of the SNPs or haplotypes were significantly associated with OCD itself. We conclude that Sapap3 is a promising functional candidate gene for human GDs, though further work is necessary to confirm this preliminary evidence of association.

Gender differences in genetic linkage and association on 11p15 in obsessive-compulsive disorder families

Several clinical and genetic studies have reported gender differences in obsessive-compulsive disorder (OCD). Previously, we conducted a linkage genome scan using multipoint allele-sharing methods to test for linkage in 219 families participating in the OCD Collaborative Genetics Study. When these families were stratified by proband's gender, suggestive linkage to chromosome 11p15 at marker D11S2362 (KAC(all) = 2.92, P = 0.00012) was detected in families with male probands, but not in the ones with female probands. We have since conducted fine mapping with a denser microsatellite marker panel in the region of 11p15, and detected a significant linkage signal at D11S4146 (KAC(all) = 5.08, P < 0.00001) in the families of male probands. Subsequently, 632 SNPs were genotyped spanning a 4.0 Mb region of the 1 LOD unit interval surrounding the linkage peak in the original families and an additional 165 families. Six SNPs were associated with OCD (P < 0.001): two SNPs were identified when all the families were included, and four SNPs only in male proband families. No SNP showed significant association with the OCD phenotype only in the families with a female proband. The results suggest a possible gender effect in the etiology of OCD.

Genomewide linkage scan for obsessive-compulsive disorder: evidence for susceptibility loci on chromosomes 3q, 7p, 1q, 15q, and 6q

Obsessive-compulsive disorder (OCD) is the tenth most disabling medical condition worldwide. Twin and family studies implicate a genetic etiology for this disorder, although specific genes have yet to be identified. Here, we present the first large-scale model-free linkage analysis of both extended and nuclear families using both 'broad' (definite and probable diagnoses) and 'narrow' (definite only) definitions of OCD. We conducted a genome-scan analysis of 219 families collected as part of the OCD Collaborative Genetics Study. Suggestive linkage signals were revealed by multipoint analysis on chromosomes 3q27-28 (P=0.0003), 6q (P=0.003), 7p (P=0.001), 1q (P=0.003), and 15q (P=0.006). Using the 'broad' OCD definition, we observed the strongest evidence for linkage on chromosome 3q27-28. The maximum overall Kong and Cox LODall score (2.67) occurred at D3S1262 and D3S2398, and simulation based P-values for these two signals were 0.0003 and 0.0004, respectively, although for both signals, the simulation-based genome-wide significance levels were 0.055. Covariate-linkage analyses implicated a possible role of gene(s) on chromosome 1 in increasing the risk for an earlier onset form of OCD. We are currently pursuing fine mapping in the five regions giving suggestive signals, with a particular focus on 3q27-28. Given probable etiologic heterogeneity in OCD, mapping gene(s) involved in the disorder may be enhanced by replication studies, large-scale family-based linkage studies, and the application of novel statistical methods.

Hoarding in obsessive compulsive disorder: results from a case-control study

Hoarding occurs relatively frequently in obsessive-compulsive disorder (OCD), and there is evidence that patients with hoarding symptoms have more severe OCD and are less responsive to treatment. In the present study, we investigated hoarding symptoms in 126 subjects with OCD. Nearly 30% of the subjects had hoarding symptoms; hoarding was twice as prevalent in males than females. Compared to the 90 non-hoarding subjects, the 36 hoarding individuals had an earlier age at onset of, and more severe, obsessive-compulsive symptoms. Hoarders had greater prevalences of symmetry obsessions, counting compulsions, and ordering compulsions. Hoarders also had greater prevalences of social phobia, personality disorders, and pathological grooming behaviors (skin picking, nail biting, and trichotillomania). Hoarding and tics were more frequent in first-degree relatives of hoarding than non-hoarding probands. The findings suggest that the treatment of OCD patients with hoarding symptoms may be complicated by more severe OCD and the presence of co-occurring disorders. Hoarding appears to be transmitted in some OCD families and may differentiate a clinical subgroup of OCD.

The familial phenotype of obsessive-compulsive disorder in relation to tic disorders: the Hopkins OCD family study

BACKGROUND

Obsessive-compulsive disorder (OCD) and tic disorders have phenomenological and familial-genetic overlaps. An OCD family study sample that excludes Tourette's syndrome in probands is used to examine whether tic disorders are part of the familial phenotype of OCD.

METHODS

Eighty case and 73 control probands and their first-degree relatives were examined by experienced clinicians using the Schedule for Affective Disorders and Schizophrenia-Lifetime Anxiety version. DSM-IV psychiatric diagnoses were ascertained by a best-estimate consensus procedure. The prevalence and severity of tic disorders, age-at-onset of OCD symptoms, and transmission of OCD and tic disorders by characteristics and type of proband (OCD + tic disorder, OCD - tic disorder) were examined in relatives.

RESULTS

Case probands and case relatives had a greater lifetime prevalence of tic disorders compared to control subjects. Tic disorders spanning a wide severity range were seen in case relatives; only mild severity was seen in control relatives. Younger age-at-onset of OCD symptoms and possibly male gender in case probands were associated with increased tic disorders in relatives. Although relatives of OCD + tic disorder and OCD - tic disorder probands had similar prevalences of tic disorders, this result is not conclusive.

CONCLUSIONS

Tic disorders constitute an alternate expression of the familial OCD phenotype.

Depth of lesion model in children and adolescents with moderate to severe traumatic brain injury: use of SPGR MRI to predict severity and outcome

OBJECTIVES

The utility of a depth of lesion classification using an SPGR MRI sequence in children with moderate to severe traumatic brain injury (TBI) was examined. Clinical and depth of lesion classification measures of TBI severity were used to predict neurological and functional outcome after TBI.

METHODS

One hundred and six children, aged 4 to 19, with moderate to severe TBI admitted to a rehabilitation unit had an SPGR MRI sequence obtained 3 months afterTBI. Acquired images were analyzed for location, number, and size of lesions. The Glasgow coma scale (GCS) was the clinical indicator of severity. The deepest lesion present was used for depth of lesion classification. Speed of injury was inferred from the type of injury. The disability rating scale at the time of discharge from the rehabilitation unit (DRS1) and at 1 year follow up (DRS2) were functional outcome measures.

RESULTS

The depth of lesion classification was significantly correlated with GCS severity, number of lesions, and both functional measures, DRS1 and DRS2. This result was more robust for time 1, probably due to the greater number of psychosocial factors impacting on functioning at time 2. Lesion volume was not correlated with the depth of lesion model. In multivariate models, depth of lesion was most predictive of DRS1, whereas GCS was most predictive of DRS2.

CONCLUSIONS

A depth of lesion classification of TBI severity may have clinical utility in predicting functional outcome in children and adolescents with moderate to severe TBI.

Pharmacological treatment of childhood obsessive-compulsive disorder: from theory to practice

Discusses pharmacological treatment of childhood obsessive-compulsive disorder (OCD), chronic and underrecognized psychiatric condition that affects up to 2% to 3% of children and adolescents. Research in OCD in children, including neuropharmacology, brain imaging, genetics, and clinical phenomenology, informs current views of OCD pathophysiology. Contemporary research supports the notion of a dysregulation in serotonin subsystems in the central nervous system, with target areas of dysfunction including basal ganglia and orbitofrontal cortex. Pharmacotherapy, along with cognitive-behavioral approaches, constitutes the indicated treatment for childhood OCD. Pharmacological treatment is best guided by a phenomenological understanding of the type of obsessions and compulsions, the intensity and frequency of their presentation with attention to behavioral reinforcements, and psychosocial factors that affect the course of the disease. Serotonin-enhancing agents, such as fluoxetine, fluvoxamine, paroxetine, and sertraline and citalopram (SSRIs) are first-line pharmacological agents, whereas refractory symptoms can be treated by augmentation with neuroleptics or other agents. Clomipramine is as effective as the SSRIs but its use may be accompanied by increased side effects. Genetic factors probably influence susceptibility to OCD as well as response to treatment, and the elucidation of these and other risk factors will be important elements in the future understanding and treatment of this disorder.

Personality disorders and normal personality dimensions in obsessive-compulsive disorder

BACKGROUND

Little is known about personality disorders and normal personality dimensions in relatives of patients with obsessive-compulsive disorder (OCD).

AIMS

To determine whether specific personality characteristics are part of a familial spectrum of OCD.

METHOD

Clinicians evaluated personality disorders in 72 OCD case and 72 control probands and 198 case and 207 control first-degree relatives. The selfcompleted Revised NEO Personality Inventory was used for assessment of normal personality dimensions. The prevalence of personality disorders and scores on normal personality dimensions were compared between case and control probands and between case and control relatives.

RESULTS

Case probands and case relatives had a high prevalence of obsessive-compulsive personality disorder (OCPD) and high neuroticism scores. Neuroticism was associated with OCPD in case but not control relatives.

CONCLUSIONS

Neuroticism and OCPD may share a common familial aetiology with OCD.

The relationship of obsessive-compulsive disorder to possible spectrum disorders: results from a family study

BACKGROUND

The familial relationship between obsessive-compulsive disorder (OCD) and "obsessive-compulsive spectrum" disorders is unclear. This study investigates the relationship of OCD to somatoform disorders (body dysmorphic disorder [BDD] and hypochondriasis), eating disorders (e.g., anorexia nervosa and bulimia nervosa), pathologic "grooming" conditions (e.g., nail biting, skin picking, trichotillomania), and other impulse control disorders (e.g., kleptomania, pathologic gambling, pyromania) using blinded family study methodology.

METHODS

Eighty case and 73 control probands, as well as 343 case and 300 control first-degree relatives, were examined by psychiatrists or Ph.D. psychologists using the Schedule for Affective Disorders and Schizophrenia-Lifetime Anxiety version. Two experienced psychiatrists independently reviewed all diagnostic information and made final consensus diagnoses using DSM-IV criteria.

RESULTS

Body dysmorphic disorder, hypochondriasis, any eating disorder, and any grooming condition occurred more frequently in case probands. In addition, BDD, either somatoform disorder, and any grooming condition occurred more frequently in case relatives, whether or not case probands also had the same diagnosis.

CONCLUSIONS

These findings indicate that certain somatoform and pathologic grooming conditions are part of the familial OCD spectrum. Though other "spectrum" conditions may resemble OCD, they do not appear to be important parts of the familial spectrum.