Analysis of shared heritability in common disorders of the brain

Disorders of the brain can exhibit considerable epidemiological comorbidity and often share symptoms, provoking debate about their etiologic overlap. We quantified the genetic sharing of 25 brain disorders from genome-wide association studies of 265,218 patients and 784,643 control participants and assessed their relationship to 17 phenotypes from 1,191,588 individuals. Psychiatric disorders share common variant risk, whereas neurological disorders appear more distinct from one another and from the psychiatric disorders. We also identified significant sharing between disorders and a number of brain phenotypes, including cognitive measures. Further, we conducted simulations to explore how statistical power, diagnostic misclassification, and phenotypic heterogeneity affect genetic correlations. These results highlight the importance of common genetic variation as a risk factor for brain disorders and the value of heritability-based methods in understanding their etiology.

Geographic patterns of genome admixture in Latin American Mestizos

The large and diverse population of Latin America is potentially a powerful resource for elucidating the genetic basis of complex traits through admixture mapping. However, no genome-wide characterization of admixture across Latin America has yet been attempted. Here, we report an analysis of admixture in thirteen Mestizo populations (i.e. in regions of mainly European and Native settlement) from seven countries in Latin America based on data for 678 autosomal and 29 X-chromosome microsatellites. We found extensive variation in Native American and European ancestry (and generally low levels of African ancestry) among populations and individuals, and evidence that admixture across Latin America has often involved predominantly European men and both Native and African women. An admixture analysis allowing for Native American population subdivision revealed a differentiation of the Native American ancestry amongst Mestizos. This observation is consistent with the genetic structure of pre-Columbian populations and with admixture having involved Natives from the area where the Mestizo examined are located. Our findings agree with available information on the demographic history of Latin America and have a number of implications for the design of association studies in population from the region.

The history of Latin America has entailed a complex process of population mixture between Native and recent immigrants across a vast geographic region. Few details are known about this process or about how it has shaped the genetic makeup of contemporary Latin American populations. To perform a broad exploration of the genetic diversity of Latin America we carried out genome-wide analyses in 13 mestizo populations sampled from 7 countries across the region. We observe a marked variation in ancestry both within and between mestizo populations. This variation in ancestry correlates with pre-Columbian Native population density in the areas examined and with recent patterns of demographic growth of the sites sampled. We also find evidence that the mixture at the origin of these populations involved mainly immigrant European men and Native and African women. Finally, mestizo populations show a differentiated Amerindian genetic background, consistent with a predominantly local Native ancestry. Mestizos thus still reveal the genetic imprint of the pre-Columbian Native American population diversification. Our study helps delineate the genetic landscape of Latin America and has a number of implications for gene identification analyses in populations from the region.

Genome-wide association study of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a common, debilitating neuropsychiatric illness with complex genetic etiology. The International OCD Foundation Genetics Collaborative (IOCDF-GC) is a multi-national collaboration established to discover the genetic variation predisposing to OCD. A set of individuals affected with DSM-IV OCD, a subset of their parents, and unselected controls, were genotyped with several different Illumina SNP microarrays. After extensive data cleaning, 1465 cases, 5557 ancestry-matched controls and 400 complete trios remained, with a common set of 469,410 autosomal and 9657 X-chromosome single nucleotide polymorphisms (SNPs). Ancestry-stratified case-control association analyses were conducted for three genetically-defined subpopulations and combined in two meta-analyses, with and without the trio-based analysis. In the case-control analysis, the lowest two P-values were located within DLGAP1 (P=2.49 × 10(-6) and P=3.44 × 10(-6)), a member of the neuronal postsynaptic density complex. In the trio analysis, rs6131295, near BTBD3, exceeded the genome-wide significance threshold with a P-value=3.84 × 10(-8). However, when trios were meta-analyzed with the case-control samples, the P-value for this variant was 3.62 × 10(-5), losing genome-wide significance. Although no SNPs were identified to be associated with OCD at a genome-wide significant level in the combined trio-case-control sample, a significant enrichment of methylation QTLs (P<0.001) and frontal lobe expression quantitative trait loci (eQTLs) (P=0.001) was observed within the top-ranked SNPs (P<0.01) from the trio-case-control analysis, suggesting these top signals may have a broad role in gene expression in the brain, and possibly in the etiology of OCD.

A patient with a resistant major depression disorder treated with deep brain stimulation in the inferior thalamic peduncle

OBJECTIVE AND IMPORTANCE

The present report explored the effect of electrical stimulation on the inferior thalamic peduncle in a patient with resistant major depression disorder (MDD).

CLINICAL PRESENTATION

This report refers to a 49-year-old woman with a history of recurrent episodes of major depression for 20 years (12 episodes and 2 hospitalizations), fulfilling Diagnostic and Statistical Manual of Mental Disorders, 4th edition, revised, criteria for MDD; in addition, the patient met criteria for borderline personality disorder and bulimia. Her longest episode of depression with suicidal ideation began 5 years before surgery. The patient's symptom array responded poorly to different combinations of antidepressants, cognitive therapy, and electroconvulsive therapy, which induced improvement only for short periods of time. Immediately before surgery, her Global Assessment of Functioning score was 20 and her Hamilton Depression Scale score ranged from 33 to 42. The patient was proposed for surgery for MDD.

INTERVENTION

The patient had bilateral eight-contact electrodes stereotactically implanted for stimulation of areas at and around the inferior thalamic peduncle. Electrode position was corroborated by unilateral electrical stimulation searching for recruiting responses and regional direct current shifts in the electroencephalogram. Recording electrodes were replaced by tetrapolar electrodes for deep brain stimulation and connected to an internalized stimulation system for continuous bipolar stimulation at 130 Hz, 0.45 milliseconds, 2.5 V. Bimonthly follow-up included psychiatric and neuropsychological evaluations performed over the course of 24 months. After 8 months of ON stimulation, the patient entered a double-blind protocol with stimulators turned OFF. Improvement of depression measured by the Hamilton Depression Scale score was evident after initial placement of electrodes without electrical stimulation. Depression relapsed partially at the end of the first week. Electrical stimulation further improved depression, normalizing depression scores and neuropsychological performance. Patient depression scores ranked between 2 and 8 during 8 months of ON stimulation without antidepressant medication. After stimulation was turned OFF, spontaneous fluctuations in patient symptoms reflected by Hamilton Depression Scale and Global Assessment of Functioning scores were documented; these fluctuations disappeared after stimulation was turned on by Month 20.

CONCLUSION

Complicated patients with comorbid conditions are common referrals to psychosurgery services. In this report, we present promising results of electrical stimulation of the inferior thalamic peduncle to treat recurrent unipolar depression in a patient with MDD and borderline personality disorder who responded poorly to treatment.

Meta-analysis of 32 genome-wide linkage studies of schizophrenia

A genome scan meta-analysis (GSMA) was carried out on 32 independent genome-wide linkage scan analyses that included 3255 pedigrees with 7413 genotyped cases affected with schizophrenia (SCZ) or related disorders. The primary GSMA divided the autosomes into 120 bins, rank-ordered the bins within each study according to the most positive linkage result in each bin, summed these ranks (weighted for study size) for each bin across studies and determined the empirical probability of a given summed rank (P(SR)) by simulation. Suggestive evidence for linkage was observed in two single bins, on chromosomes 5q (142-168 Mb) and 2q (103-134 Mb). Genome-wide evidence for linkage was detected on chromosome 2q (119-152 Mb) when bin boundaries were shifted to the middle of the previous bins. The primary analysis met empirical criteria for 'aggregate' genome-wide significance, indicating that some or all of 10 bins are likely to contain loci linked to SCZ, including regions of chromosomes 1, 2q, 3q, 4q, 5q, 8p and 10q. In a secondary analysis of 22 studies of European-ancestry samples, suggestive evidence for linkage was observed on chromosome 8p (16-33 Mb). Although the newer genome-wide association methodology has greater power to detect weak associations to single common DNA sequence variants, linkage analysis can detect diverse genetic effects that segregate in families, including multiple rare variants within one locus or several weakly associated loci in the same region. Therefore, the regions supported by this meta-analysis deserve close attention in future studies.

Partitioning the heritability of Tourette syndrome and obsessive compulsive disorder reveals differences in genetic architecture

The direct estimation of heritability from genome-wide common variant data as implemented in the program Genome-wide Complex Trait Analysis (GCTA) has provided a means to quantify heritability attributable to all interrogated variants. We have quantified the variance in liability to disease explained by all SNPs for two phenotypically-related neurobehavioral disorders, obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS), using GCTA. Our analysis yielded a heritability point estimate of 0.58 (se = 0.09, p = 5.64e-12) for TS, and 0.37 (se = 0.07, p = 1.5e-07) for OCD. In addition, we conducted multiple genomic partitioning analyses to identify genomic elements that concentrate this heritability. We examined genomic architectures of TS and OCD by chromosome, MAF bin, and functional annotations. In addition, we assessed heritability for early onset and adult onset OCD. Among other notable results, we found that SNPs with a minor allele frequency of less than 5% accounted for 21% of the TS heritability and 0% of the OCD heritability. Additionally, we identified a significant contribution to TS and OCD heritability by variants significantly associated with gene expression in two regions of the brain (parietal cortex and cerebellum) for which we had available expression quantitative trait loci (eQTLs). Finally we analyzed the genetic correlation between TS and OCD, revealing a genetic correlation of 0.41 (se = 0.15, p = 0.002). These results are very close to previous heritability estimates for TS and OCD based on twin and family studies, suggesting that very little, if any, heritability is truly missing (i.e., unassayed) from TS and OCD GWAS studies of common variation. The results also indicate that there is some genetic overlap between these two phenotypically-related neuropsychiatric disorders, but suggest that the two disorders have distinct genetic architectures.

Neurocognitive endophenotypes for bipolar disorder identified in multiplex multigenerational families

CONTEXT

Although genetic influences on bipolar disorder are well established, localization of genes that predispose to the illness has proven difficult. Given that genes predisposing to bipolar disorder may be transmitted without expression of the categorical clinical phenotype, a strategy for identifying risk genes is to identify and map quantitative intermediate phenotypes or endophenotypes.

OBJECTIVE

To adjudicate neurocognitive endophenotypes for bipolar disorder.

DESIGN

All participants underwent diagnostic interviews and comprehensive neurocognitive evaluations. Neurocognitive measures found to be heritable were entered into analyses designed to determine which test results are impaired in affected individuals, are sensitive to the genetic liability for the illness, and are genetically correlated with affection status.

SETTING

Central valley of Costa Rica; Mexico City, Mexico; and San Antonio, Texas.

PARTICIPANTS

Seven hundred nine Latino individuals participated in the study. Of these, 660 were members of extended pedigrees with at least 2 siblings diagnosed as having bipolar disorder (n = 230). The remaining subjects were community control subjects drawn from each site who did not have a personal or family history of bipolar disorder or schizophrenia.

MAIN OUTCOME MEASURE

Neurocognitive test performance.

RESULTS

Two of the 22 neurocognitive variables were not significantly heritable and were excluded from subsequent analyses. Patients with bipolar disorder were impaired on 6 cognitive measures compared with nonrelated healthy controls. Nonbipolar first-degree relatives were impaired on 5 of these, and the following 3 tests were genetically correlated with affection status: Digit Symbol Coding Task, Object Delayed Response Task, and immediate facial memory.

CONCLUSION

This large-scale extended pedigree study of cognitive functioning in bipolar disorder identifies measures of processing speed, working memory, and declarative (facial) memory as candidate endophenotypes for bipolar disorder.

Evidence for genetic heterogeneity between clinical subtypes of bipolar disorder

We performed a genome-wide association study of 6447 bipolar disorder (BD) cases and 12 639 controls from the International Cohort Collection for Bipolar Disorder (ICCBD). Meta-analysis was performed with prior results from the Psychiatric Genomics Consortium Bipolar Disorder Working Group for a combined sample of 13 902 cases and 19 279 controls. We identified eight genome-wide significant, associated regions, including a novel associated region on chromosome 10 (rs10884920; P=3.28 × 10-8) that includes the brain-enriched cytoskeleton protein adducin 3 (ADD3), a non-coding RNA, and a neuropeptide-specific aminopeptidase P (XPNPEP1). Our large sample size allowed us to test the heritability and genetic correlation of BD subtypes and investigate their genetic overlap with schizophrenia and major depressive disorder. We found a significant difference in heritability of the two most common forms of BD (BD I SNP-h2=0.35; BD II SNP-h2=0.25; P=0.02). The genetic correlation between BD I and BD II was 0.78, whereas the genetic correlation was 0.97 when BD cohorts containing both types were compared. In addition, we demonstrated a significantly greater load of polygenic risk alleles for schizophrenia and BD in patients with BD I compared with patients with BD II, and a greater load of schizophrenia risk alleles in patients with the bipolar type of schizoaffective disorder compared with patients with either BD I or BD II. These results point to a partial difference in the genetic architecture of BD subtypes as currently defined.

Copy number variation in obsessive-compulsive disorder and tourette syndrome: a cross-disorder study

OBJECTIVE

Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are heritable neurodevelopmental disorders with a partially shared genetic etiology. This study represents the first genome-wide investigation of large (>500 kb), rare (<1%) copy number variants (CNVs) in OCD and the largest genome-wide CNV analysis in TS to date.

METHOD

The primary analyses used a cross-disorder design for 2,699 case patients (1,613 ascertained for OCD, 1,086 ascertained for TS) and 1,789 controls. Parental data facilitated a de novo analysis in 348 OCD trios.

RESULTS

Although no global CNV burden was detected in the cross-disorder analysis or in secondary, disease-specific analyses, there was a 3.3-fold increased burden of large deletions previously associated with other neurodevelopmental disorders (p = .09). Half of these neurodevelopmental deletions were located in a single locus, 16p13.11 (5 case patient deletions: 0 control deletions, p = .08 in the current study, p = .025 compared to published controls). Three 16p13.11 deletions were confirmed de novo, providing further support for the etiological significance of this region. The overall OCD de novo rate was 1.4%, which is intermediate between published rates in controls (0.7%) and in individuals with autism or schizophrenia (2-4%).

CONCLUSION

Several converging lines of evidence implicate 16p13.11 deletions in OCD, with weaker evidence for a role in TS. The trend toward increased overall neurodevelopmental CNV burden in TS and OCD suggests that deletions previously associated with other neurodevelopmental disorders may also contribute to these phenotypes.

Cross-disorder genome-wide analyses suggest a complex genetic relationship between Tourette's syndrome and OCD

OBJECTIVE

Obsessive-compulsive disorder (OCD) and Tourette's syndrome are highly heritable neurodevelopmental disorders that are thought to share genetic risk factors. However, the identification of definitive susceptibility genes for these etiologically complex disorders remains elusive. The authors report a combined genome-wide association study (GWAS) of Tourette's syndrome and OCD.

METHOD

The authors conducted a GWAS in 2,723 cases (1,310 with OCD, 834 with Tourette's syndrome, 579 with OCD plus Tourette's syndrome/chronic tics), 5,667 ancestry-matched controls, and 290 OCD parent-child trios. GWAS summary statistics were examined for enrichment of functional variants associated with gene expression levels in brain regions. Polygenic score analyses were conducted to investigate the genetic architecture within and across the two disorders.

RESULTS

Although no individual single-nucleotide polymorphisms (SNPs) achieved genome-wide significance, the GWAS signals were enriched for SNPs strongly associated with variations in brain gene expression levels (expression quantitative loci, or eQTLs), suggesting the presence of true functional variants that contribute to risk of these disorders. Polygenic score analyses identified a significant polygenic component for OCD (p=2×10(-4)), predicting 3.2% of the phenotypic variance in an independent data set. In contrast, Tourette's syndrome had a smaller, nonsignificant polygenic component, predicting only 0.6% of the phenotypic variance (p=0.06). No significant polygenic signal was detected across the two disorders, although the sample is likely underpowered to detect a modest shared signal. Furthermore, the OCD polygenic signal was significantly attenuated when cases with both OCD and co-occurring Tourette's syndrome/chronic tics were included in the analysis (p=0.01).

CONCLUSIONS

Previous work has shown that Tourette's syndrome and OCD have some degree of shared genetic variation. However, the data from this study suggest that there are also distinct components to the genetic architectures of these two disorders. Furthermore, OCD with co-occurring Tourette's syndrome/chronic tics may have different underlying genetic susceptibility compared with OCD alone.

Increased prevalence of the seven-repeat variant of the dopamine D4 receptor gene in patients with obsessive-compulsive disorder with tics

The polymorphism characterized by a varying number of 48 bp repeats (VNTR) in the dopamine D4 receptor (DRD4) gene was examined in 61 obsessive-compulsive disorder (OCD) probands with and without tics. Most of the OCD patients with tics showed at least one copy of the 7-fold variant compared to those affected subjects without tics (91 vs. 48%, respectively, Yates corrected chi2 = 5.54, P = 0.018). Similarly, a higher number of copies of this common variant were detected in the group of probands displaying tics compared to those OCD's without tics (Yates corrected chi2 = 4.66, P = 0.03). Our study suggests that the seven-repeat allele of the DRD4 gene could be a factor in the phenotypic variance of tics among OCD individuals.

Adjudicating neurocognitive endophenotypes for schizophrenia

Although genetic influences on schizophrenia are well established, localization of the genes responsible for this illness has proven extremely difficult. Given evidence that genes predisposing to schizophrenia may be transmitted without expression of the clinical phenotype, efforts have focused on developing endophenotypes. While several neuropsychological measures have been proposed to be endophenotypes, few studies have systematically assessed batteries of neurocognitive tests to determine which tests are most sensitive to liability for the illness. Two hundred sixty-nine Latino individuals were administered a standard neuropsychological battery. Two hundred fourteen of these were members of families with at least two siblings diagnosed with schizophrenia or schizoaffective disorder. The remaining were community controls without history of major psychiatric illness. Neurocognitive measures found to be heritable were entered into analyses designed to determine which tests covary with the degree of genetic relationship to affected individuals. Although five measures were found to uniquely model genetic liability for schizophrenia, digit symbol coding was the most sensitive. To assess the specificity of these endophenotypes, performance on these measures were compared to family members with bipolar and unipolar affective disorders. These markers clearly distinguished between individuals with psychotic illnesses and those with major depression. As measures contributed uniquely to discriminate individuals at varying risk for schizophrenia, our findings imply multiple independently inherited elements to the liability for the illness. We present a practical model for adjudicating endophenotypes and determining which measures are best suited for use in linkage analyses.

Contributions of common genetic variants to risk of schizophrenia among individuals of African and Latino ancestry

Schizophrenia is a common, chronic and debilitating neuropsychiatric syndrome affecting tens of millions of individuals worldwide. While rare genetic variants play a role in the etiology of schizophrenia, most of the currently explained liability is within common variation, suggesting that variation predating the human diaspora out of Africa harbors a large fraction of the common variant attributable heritability. However, common variant association studies in schizophrenia have concentrated mainly on cohorts of European descent. We describe genome-wide association studies of 6152 cases and 3918 controls of admixed African ancestry, and of 1234 cases and 3090 controls of Latino ancestry, representing the largest such study in these populations to date. Combining results from the samples with African ancestry with summary statistics from the Psychiatric Genomics Consortium (PGC) study of schizophrenia yielded seven newly genome-wide significant loci, and we identified an additional eight loci by incorporating the results from samples with Latino ancestry. Leveraging population differences in patterns of linkage disequilibrium, we achieve improved fine-mapping resolution at 22 previously reported and 4 newly significant loci. Polygenic risk score profiling revealed improved prediction based on trans-ancestry meta-analysis results for admixed African (Nagelkerke's R2 = 0.032; liability R2 = 0.017; P < 10-52), Latino (Nagelkerke's R2 = 0.089; liability R2 = 0.021; P < 10-58), and European individuals (Nagelkerke's R2 = 0.089; liability R2 = 0.037; P < 10-113), further highlighting the advantages of incorporating data from diverse human populations.

Neuromodulation of the inferior thalamic peduncle for major depression and obsessive compulsive disorder

Neuromodulation of the inferior thalamic peduncle is a new surgical treatment for major depression and obsessive-compulsive disorder. The inferior thalamic peduncle is a bundle of fibers connecting the orbito-frontal cortex with the non-specific thalamic system in a small area behind the fornix and anterior to the polar reticular thalamic nucleus. Electrical stimulation elicits characteristic frontal cortical responses (recruiting responses and direct current (DC)-shift) that confirm correct localization of this anatomical structure. A female with depression for 23 years and a male with obsessive-compulsive disorder for 9 years had stereotactic implantation of electrodes in the inferior thalamic peduncle and were evaluated over a long-term period. Initial OFF stimulation period (1 month) showed no consistent changes in the Hamilton Depression Scale (HAM-D), Yale Brown Obsessive Compulsive Scale (YBOCS), or Global Assessment of Functioning scale (GAF). The ON stimulation period (3-5 V, 130-Hz frequency, 450-msec pulse width in a continuous program) showed significant decrease in depression, obsession, and compulsion symptoms. GAF improved significantly in both cases. The neuropsychological tests battery showed no significant changes except from a reduction in the perseverative response of the obsessive-compulsive patient and better performance in manual praxias of the female depressive patient. Moderate increase in weight (5 kg on average) was observed in both cases.

Overview of genetics and obsessive-compulsive disorder

This paper reviews the current state of research into the genetics of obsessive-compulsive disorder (OCD). Heredity has a major role in OCD etiology. This evidence comes from several methodological approaches such as family, twin, and segregation analysis studies. A major single gene effect as well as a polygenic hypothesis has been suggested based on segregation studies. In addition, candidate gene association and linkage analyses have shown not only one gene, but a few interesting genes and areas of the genome that may be relevant in OCD. In this search for genes, new definitions of the OCD phenotype have emerged, and some of them may be considered intermediate phenotypes between the gene effect and OCD-DSM-IV diagnosis. The phenotypic and genetic heterogeneity of OCD magnifies the challenge of locating susceptibility genes; at the same time, the identification of vulnerability genes will elucidate the identification of subtypes or dimensions of the disorder. Therefore research strategies that take advantage of clinical subtyping and that redefine the OCD phenotype in the context of genetic studies may potentially contribute to the nosology of OCD and ultimately pathophysiology. There is a lack of understanding about how genes and environment interact in OCD. However, there are some reports that will be discussed, which have attempted to evaluate how the environment contributes to OCD.

Electrical stimulation of the inferior thalamic peduncle in the treatment of major depression and obsessive compulsive disorders

OBJECTIVE

Stimulation of the inferior thalamic peduncle (ITP) is emerging as a promising new therapeutic target in certain psychiatric disorders. The circuitry that includes the nonspecific thalamic system (NSTS), which projects via the ITP to the orbitofrontal cortex (OFC), is involved in the physiopathology of major depression disorder (MDD) and obsessive compulsive disorder (OCD). The safety and efficacy of chronic ITP stimulation in cases of MDD and OCD refractory to medical treatment is presented.

MATERIALS AND METHODS

Six patients with OCD and one with MDD were implanted with tetrapolar deep brain stimulation electrodes in the ITP (x = 3.5 mm lateral to the ventricular wall, y = 5 mm behind the anterior commissure, and z = at the intercommissural plane, i.e., anterior commissure-posterior commissure [AC-PC] level). The effect of chronic stimulation at 130 Hz, 450 μs, and 5.0 V on OCD was evaluated before and 3, 6, and 12 months after initiation of electrical stimulation through the Yale-Brown Obsessive Compulsive Scale, Hamilton Depression Rating Scale, and Global Assessment of Function scale.

RESULTS

Chronic ITP electrical stimulation in OCD patients decreased the mean Yale-Brown Obsessive Compulsive Scale score to around 51% for the group at the 12-month follow-up, and increased the mean Global Assessment of Function scale score to 68% for a significant improvement (P = 0.026). Three of 6 patients returned to work. The Hamilton Depression Rating Scale score of the only patient with MDD treated to date went from 42 to 6. This condition of the patient, who had been incapacitated for 5 years prior to surgery, has not relapsed for 9 years. Three OCD patients with drug addiction continued to consume drugs in spite of their improvement in OCD.

CONCLUSION

Deep brain stimulation in the ITP is safe and may be effective in the treatment of OCD. A multicenter evaluation of the safety and efficacy of ITP in OCD is currently in process.

A forced five-dimensional factor analysis and concurrent validity of the Positive and Negative Syndrome Scale in Mexican schizophrenic patients

The heterogeneity of schizophrenic symptomatology is well documented. The positive-negative distinction is limited to cover the entire spectrum of schizophrenic psychopathology in order to describe the various clinical aspects of the disorder.

METHOD

We recruited 150 schizophrenic patients between May 2002 and September 2003. Diagnoses were based on a structured clinical interview. The Positive and Negative Syndrome Scale (PANSS) was used to evaluate general psychopathology and symptom severity. For the concurrent validity of the pentagonal model of the PANSS, the BPRS, the CDSS, the OAS and the MMSE were used.

RESULTS

The forced five-factor principal-component analysis explained 53.4% of the total variance. There were significant correlations between the clinical rating scales and the five components of the PANSS.

DISCUSSION

Our data support a pentagonal model underlying the multidimensional schizophrenic symptomatology as assessed by the PANSS. The five-factor structure of the PANSS in Mexican schizophrenic patients enables further elucidation of the various clinical aspects of schizophrenia.

The genomic psychiatry cohort: partners in discovery

The Genomic Psychiatry Cohort (GPC) is a longitudinal resource designed to provide the necessary population-based sample for large-scale genomic studies, studies focusing on Research Domain Criteria (RDoC) and/or other alternate phenotype constructs, clinical and interventional studies, nested case-control studies, long-term disease course studies, and genomic variant-to-phenotype studies. We provide and will continue to encourage access to the GPC as an international resource. DNA and other biological samples and diagnostic data are available through the National Institute of Mental Health (NIMH) Repository. After appropriate review and approval by an advisory board, investigators are able to collaborate in, propose, and co-lead studies involving cohort participants.

Preliminary study in patients with obsessive-compulsive disorder treated with electrical stimulation in the inferior thalamic peduncle

OBJECTIVE

Deep brain stimulation has been used in the treatment of refractory obsessive-compulsive disorder (OCD). Our principal objective was to determine the safety and effectiveness of deep brain stimulation of the inferior thalamic peduncle in the treatment of refractory OCD.

METHODS

An open protocol was performed from March 2003 to April 2007 in 5 patients with OCD refractory to conventional treatments. Bilateral stereotactic implantation of tetrapolar electrodes was aimed at the inferior thalamic peduncle and corroborated by electrophysiological responses and magnetic resonance imaging. All patients were off stimulation for 1 month after implantation. In the on-stimulation period, parameters were set at 5 V, 450 microseconds, 130 Hz in bipolar and continuous mode. Clinical changes were evaluated every 3 months for 12 months by means of the Yale-Brown Obsessive Compulsive Scale and the Global Assessment of Functioning scale. Statistical significance was assessed by the Friedman and Wilcoxon tests.

RESULTS

The mean Yale-Brown Obsessive Compulsive Scale score decreased from 35 to 17.8 (P < 0.001), and the mean Global Assessment of Functioning scale score improved from 20% to 70% (P < 0.0001). The neuropsychological battery did not show significant changes, and there were no side effects related to electrical stimulation in the chronic period.

CONCLUSION

We conclude that inferior thalamic peduncle stimulation is a safe procedure and may be an effective alternative in the treatment of those OCD cases refractory to conventional treatments.

Additional evidence that genetic variation of MAO-A gene supports a gender subtype in obsessive-compulsive disorder

Studies have recently reported a sexually dimorphic association between obsessive-compulsive disorder (OCD) and a polymorphism related with variations in MAO-A activity. These observations suggest the possibility of gender differences in genetic susceptibility for OCD. We thus reexamined the MAO-A/EcoRV polymorphism in a sample of 122 OCD patients and 124 healthy subjects. An excess of allele 1 in OCD females with major depression disorder was confirmed as previously reported. This difference was more strongly associated with OCD females than males in the total sample. Finally, we analyzed a sample of 51 OCD trios. Haplotype-based haplotype relative risk (HHRR) analysis of the inheritance of the MAO-A variants revealed in the female probands that 14 out of 19 transmitted the allele 1, providing significant evidence for an allelic association between OCD and MAO-A gene. In conclusion, our findings may provide molecular evidence to identify a clinically meaningful gender subtype. However, an effort should be made to replicate the analysis in larger samples of informative parents using strategies such as transmission disequilibrium test to allow definite conclusions.

Randomized controlled pilot study of quetiapine in the treatment of adolescent conduct disorder

OBJECTIVE

The aim of this study was to examine whether quetiapine is superior to placebo in the treatment of adolescents with conduct disorder.

METHODS

This was a 7-week, randomized, double-blind, placebo-controlled pilot study with two parallel arms. Nine youths were randomly assigned to receive quetiapine, and 10 youths were randomly assigned to receive placebo. Patients were assessed weekly throughout the trial. Quetiapine was dosed twice daily, and medications could be titrated flexibly through the end of study week 5. The dose was fixed for the final 2 weeks of the study. The primary outcome measures were the clinician-assessed Clinical Global Impressions-Severity (CGI-S) and-Improvement (CGI-I) scales. Secondary outcome measures included parent-assessed quality of life, the overt aggression scale (OAS), and the conduct problems subscale of the Conners' Parent Rating Scale (CPRS-CP).

RESULTS

The final mean dose of quetiapine was 294 +/- 78 mg/day (range 200-600 mg/day). Quetiapine was superior to placebo on all clinician-assessed measures and on the parent-assessed quality of life rating scale. No differences were found on the parent-completed OAS and CPRS-CP. Quetiapine was well tolerated. One patient randomized to quetiapine developed akathisia, requiring medication discontinuation. No other extrapyramidal side effects occurred in patients receiving active drug.

CONCLUSIONS

This methodologically controlled pilot study provides data that quetiapine may have efficacy in the treatment of adolescents with conduct disorder. Because of the preliminary nature of the study, further research with larger samples is needed to confirm these findings.

Association study of the serotonin transporter gene polymorphism in obsessive-compulsive disorder

The hypothesis implicating the serotonergic system in the pathophysiology of obsessive-compulsive disorder (OCD) is supported by the therapeutic efficacy of selective serotonin reuptake inhibitors (SSRIs). Since SSRIs act on the serotonin transporter (5-HTT), it has been suggested that the 5-HTT gene (SCL6A4) could be a good candidate for OCD. The SCL6A4 gene has a 44-bp insertion/deletion polymorphism in its promoter region (5-HTTLPR). Previous studies have revealed an association between OCD and the l allele. We analysed the 5-HTTLPR polymorphic system in 115 Mexican OCD patients and 136 controls. No significant association was found between l allele and OCD (chi2 = 1.54, d.f. = 1, p = 0.21). Furthermore, we assessed alternative methods that employ family-based designs in a sample of 43 trios. Haplotype-based haplotype relative risk and transmission disequilibrium analysis did not show a preferential transmission of l allele to OCD probands. Our results indicate the need to analyse larger samples using family-based methods.

Contribution of Rare Copy Number Variants to Bipolar Disorder Risk Is Limited to Schizoaffective Cases

BACKGROUND

Genetic risk for bipolar disorder (BD) is conferred through many common alleles, while a role for rare copy number variants (CNVs) is less clear. Subtypes of BD including schizoaffective disorder bipolar type (SAB), bipolar I disorder (BD I), and bipolar II disorder (BD II) differ according to the prominence and timing of psychosis, mania, and depression. The genetic factors contributing to the combination of symptoms among these subtypes are poorly understood.

METHODS

Rare large CNVs were analyzed in 6353 BD cases (3833 BD I [2676 with psychosis, 850 without psychosis, and 307 with unknown psychosis history], 1436 BD II, 579 SAB, and 505 BD not otherwise specified) and 8656 controls. CNV burden and a polygenic risk score (PRS) for schizophrenia were used to evaluate the relative contributions of rare and common variants to risk of BD, BD subtypes, and psychosis.

RESULTS

CNV burden did not differ between BD and controls when treated as a single diagnostic entity. However, burden in SAB was increased relative to controls (p = .001), BD I (p = .0003), and BD II (p = .0007). Burden and schizophrenia PRSs were increased in SAB compared with BD I with psychosis (CNV p = .0007, PRS p = .004), and BD I without psychosis (CNV p = .0004, PRS p = 3.9 × 10-5). Within BD I, psychosis was associated with increased schizophrenia PRSs (p = .005) but not CNV burden.

CONCLUSIONS

CNV burden in BD is limited to SAB. Rare and common genetic variants may contribute differently to risk for psychosis and perhaps other classes of psychiatric symptoms.

A family-based association study of the 5-HT-1Dbeta receptor gene in obsessive-compulsive disorder

Pharmacological studies have shown that sumatriptan, a selective ligand of the serotonin 5-HT-1Dbeta autoreceptor, modifies obsessive-compulsive disorder (OCD) symptoms. The current study analysed the G861C polymorphism of the 5-HT-1Dbeta gene in a sample of 72 trios. Genotyping data were analysed using the Family-Based Association Test (FBAT). We did not replicate the previously reported linkage disequilibrium between the G861 variant and OCD. However, a quantitative trait analysis, assessing severity of OCD symptoms and defined as YBOCS score, confirmed the finding that subjects with a preferential transmission of the G861 variant showed higher YBOCS Obsession scores compared to patients carrying the C861 allele. These preliminary findings may indicate that the 5-HT-1Dbeta receptor gene could be involved in the severity of obsession symptoms in OCD. However, it is important to perform the replication of these findings in larger sample sizes of informative families.