The network structure of mania symptoms differs between people with and without binge eating

OBJECTIVES

People with bipolar disorder who also report binge eating have increased psychopathology and greater impairment than those without binge eating. Whether this co-occurrence is related to binge eating as a symptom or presents differently across full-syndrome eating disorders with binge eating is unclear.

METHODS

We first compared networks of 13 lifetime mania symptoms in 34,226 participants from the United Kingdom's National Institute for Health and Care Research BioResource with (n = 12,104) and without (n = 22,122) lifetime binge eating. Second, in the subsample with binge eating, we compared networks of mania symptoms in participants with lifetime anorexia nervosa binge-eating/purging (n = 825), bulimia nervosa (n = 3737), and binge-eating disorder (n = 3648).

RESULTS

People with binge eating endorsed every mania symptom significantly more often than those without binge eating. Within the subsample, people with bulimia nervosa most often had the highest endorsement rate of each mania symptom. We found significant differences in network parameter statistics, including network structure (M = 0.25, p = 0.001) and global strength (S = 1.84, p = 0.002) when comparing the binge eating with no binge-eating participants. However, network structure differences were sensitive to reductions in sample size and the greater density of the latter network was explained by the large proportion of participants (34%) without mania symptoms. The structure of the anorexia nervosa binge-eating/purging network differed from the bulimia nervosa network (M = 0.66, p = 0.001), but the result was unstable.

CONCLUSIONS

Our results suggest that the presence and structure of mania symptoms may be more associated with binge eating as a symptom rather than any specific binge-type eating disorder. Further research with larger sample sizes is required to confirm our findings.

Genetic examination of the Mood Disorder Questionnaire and its relationship with bipolar disorder

The Mood Disorder Questionnaire (MDQ) is a common screening tool for bipolar disorder that assesses manic symptoms. Its utility for genetic studies of mania or bipolar traits has not been fully examined. We psychometrically compared the MDQ to self-reported bipolar disorder in participants from the United Kingdom National Institute of Health and Care Research Mental Health BioResource. We conducted genome-wide association studies of manic symptom quantitative traits and symptom subgroups, derived from the MDQ items (N = 11,568-19,859). We calculated genetic correlations with bipolar disorder and other psychiatric and behavioral traits. The MDQ screener showed low positive predictive value (0.29) for self-reported bipolar disorder. Neither concurrent nor lifetime manic symptoms were genetically correlated with bipolar disorder. Lifetime manic symptoms had a highest genetic correlation (rg  = 1.0) with posttraumatic stress disorder although this was not confirmed by within-cohort phenotypic correlations (rp  = 0.41). Other significant genetic correlations included attention deficit hyperactivity disorder (rg  = 0.69), insomnia (rg  = 0.55), and major depressive disorder (rg  = 0.42). Our study adds to existing literature questioning the MDQ's validity and suggests it may capture symptoms of general distress or psychopathology, rather than hypomania/mania specifically, in at-risk populations.

Depression, anxiety and PTSD symptoms before and during the COVID-19 pandemic in the UK

BACKGROUND

The impact of the coronavirus disease 2019 (COVID-19) pandemic on mental health is still being unravelled. It is important to identify which individuals are at greatest risk of worsening symptoms. This study aimed to examine changes in depression, anxiety and post-traumatic stress disorder (PTSD) symptoms using prospective and retrospective symptom change assessments, and to find and examine the effect of key risk factors.

METHOD

Online questionnaires were administered to 34 465 individuals (aged 16 years or above) in April/May 2020 in the UK, recruited from existing cohorts or via social media. Around one-third (n = 12 718) of included participants had prior diagnoses of depression or anxiety and had completed pre-pandemic mental health assessments (between September 2018 and February 2020), allowing prospective investigation of symptom change.

RESULTS

Prospective symptom analyses showed small decreases in depression (PHQ-9: -0.43 points) and anxiety [generalised anxiety disorder scale - 7 items (GAD)-7: -0.33 points] and increases in PTSD (PCL-6: 0.22 points). Conversely, retrospective symptom analyses demonstrated significant large increases (PHQ-9: 2.40; GAD-7 = 1.97), with 55% reported worsening mental health since the beginning of the pandemic on a global change rating. Across both prospective and retrospective measures of symptom change, worsening depression, anxiety and PTSD symptoms were associated with prior mental health diagnoses, female gender, young age and unemployed/student status.

CONCLUSIONS

We highlight the effect of prior mental health diagnoses on worsening mental health during the pandemic and confirm previously reported sociodemographic risk factors. Discrepancies between prospective and retrospective measures of changes in mental health may be related to recall bias-related underestimation of prior symptom severity.

The United Kingdom Eating Disorders Genetics Initiative

OBJECTIVE

The United Kingdom Eating Disorders Genetics Initiative (EDGI UK), part of the National Institute for Health and Care Research (NIHR) Mental Health BioResource, aims to deepen our understanding of the environmental and genetic etiology of eating disorders. EDGI UK launched in February 2020 and is partnered with the UK eating disorders charity, Beat. Multiple EDGI branches exist worldwide. This article serves the dual function of providing an in-depth description of our study protocol and of describing our initial sample including demographics, diagnoses, and physical and psychiatric comorbidities.

METHOD

EDGI UK recruits via media and clinical services. Anyone living in England, at least 16 years old, with a lifetime probable or clinical eating disorder is eligible to sign up online: edgiuk.org. Participants complete online questionnaires, donate a saliva sample for genetic analysis, and consent to medical record linkage and recontact for future studies.

RESULTS

As of September 2022, EDGI UK recruited 7435 survey participants: 98% female, 93.1% white, 97.8% cisgender, 65.9% heterosexual, and 52.1% have a university degree. Over half (57.8%) of these participants have returned their saliva DNA kit. The most common diagnoses are anorexia nervosa (48.3%), purging disorder (37.8%), bulimia nervosa (37.5%), binge-eating disorder (15.8%), and atypical anorexia nervosa (7.8%).

CONCLUSION

EDGI UK is the largest UK eating disorders study and efforts to increase its diversity are underway. It offers a unique opportunity to accelerate eating disorder research. Researchers and participants with lived experience can collaborate on projects with unparalleled sample size.

PUBLIC SIGNIFICANCE STATEMENT

Eating disorders are debilitating and costly for society but are under-researched due to underfunding. EDGI UK is one of the largest eating disorder studies worldwide with ongoing recruitment. The collected data constitute a resource for secondary analysis. We will combine data from all international EDGI branches and the NIHR BioResource to facilitate research that improves our understanding of eating disorders and their comorbidities.

Sociodemographic, mental health, and physical health factors associated with participation within re-contactable mental health cohorts: an investigation of the GLAD Study

BACKGROUND

The Genetic Links to Anxiety and Depression (GLAD) Study is a large cohort of individuals with lifetime anxiety and/or depression, designed to facilitate re-contact of participants for mental health research. At the start of the pandemic, participants from three cohorts, including the GLAD Study, were invited to join the COVID-19 Psychiatry and Neurological Genetics (COPING) study to monitor mental and neurological health. However, previous research suggests that participation in longitudinal studies follows a systematic, rather than random, process, which can ultimately bias results. Therefore, this study assessed participation biases following the re-contact of GLAD Study participants.

METHODS

In April 2020, all current GLAD Study participants (N = 36,770) were invited to the COPING study. Using logistic regression, we investigated whether sociodemographic, mental, and physical health characteristics were associated with participation in the COPING baseline survey (aim one). Subsequently, we used a zero-inflated negative binomial regression to examine whether these factors were also related to participation in the COPING follow-up surveys (aim two).

RESULTS

For aim one, older age, female gender identity, non-binary or self-defined gender identities, having one or more physical health disorders, and providing a saliva kit for the GLAD Study were associated with an increased odds of completing the COPING baseline survey. In contrast, lower educational attainment, Asian or Asian British ethnic identity, Black or Black British ethnic identity, higher alcohol consumption at the GLAD sign-up survey, and current or ex-smoking were associated with a reduced odds. For aim two, older age, female gender, and saliva kit provision were associated with greater COPING follow-up survey completion. Lower educational attainment, higher alcohol consumption at the GLAD Study sign-up, ex-smoking, and self-reported attention deficit hyperactivity disorder had negative relationships.

CONCLUSIONS

Participation biases surrounding sociodemographic and physical health characteristics were particularly evident when re-contacting the GLAD Study volunteers. Factors associated with participation may vary depending on study design. Researchers should examine the barriers and mechanisms underlying participation bias in order to combat these issues and address recruitment biases in future studies.

Factors associated with anxiety disorder comorbidity

BACKGROUND

Anxiety and depressive disorders often co-occur and the order of their emergence may be associated with different clinical outcomes. However, minimal research has been conducted on anxiety-anxiety comorbidity. This study examined factors associated with anxiety comorbidity and anxiety-MDD temporal sequence.

METHODS

Online, self-report data were collected from the UK-based GLAD and COPING NBR cohorts (N = 38,775). Logistic regression analyses compared differences in sociodemographic, trauma, and clinical factors between single anxiety, anxiety-anxiety comorbidity, anxiety-MDD (major depressive disorder) comorbidity, and MDD-only. Additionally, anxiety-first and MDD-first anxiety-MDD were compared. Differences in familial risk were assessed in those participants with self-reported family history or genotype data.

RESULTS

Anxiety-anxiety and anxiety-MDD had higher rates of self-reported anxiety or depressive disorder diagnoses, younger age of onset, and higher recurrence than single anxiety. Anxiety-MDD displayed greater clinical severity/complexity than MDD only. Anxiety-anxiety had more severe current anxiety symptoms, less severe current depressive symptoms, and reduced likelihood of self-reporting an anxiety/depressive disorder diagnosis than anxiety-MDD. Anxiety-first anxiety-MDD had a younger age of onset, more severe anxiety symptoms, and less likelihood of self-reporting a diagnosis than MDD-first. Minimal differences in familial risk were found.

LIMITATIONS

Self-report, retrospective measures may introduce recall bias. The familial risk analyses were likely underpowered.

CONCLUSIONS

Anxiety-anxiety comorbidity displayed a similarly severe and complex profile of symptoms as anxiety-MDD but distinct features. For anxiety-MDD, first-onset anxiety had an earlier age of onset and greater severity than MDD-first. Anxiety disorders and comorbidity warrant further investigation and attention in research and practice.

Design of an adaptive randomized clinical trial of intravenous citrulline for sickle cell pain crisis in the emergency department

Background

Vaso-occlusive pain crisis (VOC) is the most frequent cause for Emergency Department (ED) visits and hospital admissions for patients with sickle cell disease (SCD). Nitric oxide plays a critical role in the pathogenesis of vaso-occlusion. The amino acid, citrulline, is the main endothelial nitric oxide booster that offers the potential to ameliorate vaso-occlusion and decrease the risk of hospitalization.

Objective

In this two-part study, the goal of the first part is to determine the pharmacokinetic profile of intravenous (IV) l-citrulline and optimal dose for the second part of the study, which is to determine the efficacy and tolerability of the intervention in patients with SCD.

Design

A phase I/IIA open-label dose-finding study with subsequent double-blind, placebo-controlled, randomized Study of l-citrulline in children and adolescents with SCD presenting to the ED in VOC.

Methods

Part 1: Subjects experiencing VOC are enrolled in an open-label, ascending dose of IV l-citrulline to identify the optimum dose with endpoints of pharmacokinetic parameters, pain scores, reduction of opioid use, quality of life, proportion admitted to the hospital for treatment of pain, readmission rates, and assessment of adverse events. Part 2 of the trial is a double-blind, placebo-controlled adaptive "pick-the-winner" design to evaluate the efficacy and tolerability of IV l-citrulline in patients with SCD while receiving standard of care therapy for VOC.

Summary

This ED based sickle cell adaptive trial will determine the optimal dose for IV citrulline and whether the intervention improves outcome as a potential novel therapy for VOC in SCD.

Risk and protective factors for new-onset binge eating, low weight, and self-harm symptoms in >35,000 individuals in the UK during the COVID-19 pandemic

OBJECTIVE

The disruption caused by the COVID-19 pandemic has been associated with poor mental health, including increases in eating disorders and self-harm symptoms. We investigated risk and protective factors for the new onset of these symptoms during the pandemic.

METHOD

Data were from the COVID-19 Psychiatry and Neurological Genetics study and the Repeated Assessment of Mental health in Pandemics Study (n = 36,715). Exposures were socio-demographic characteristics, lifetime psychiatric disorder, and COVID-related variables, including SARS-CoV-2 infection/illness with COVID-19. We identified four subsamples of participants without pre-pandemic experience of our outcomes: binge eating (n = 24,211), low weight (n = 24,364), suicidal and/or self-harm ideation (n = 18,040), and self-harm (n = 29,948). Participants reported on our outcomes at frequent intervals (fortnightly to monthly). We fitted multiple logistic regression models to identify factors associated with the new onset of our outcomes.

RESULTS

Within each subsample, new onset was reported by: 21% for binge eating, 10.8% for low weight, 23.5% for suicidal and/or self-harm ideation, and 3.5% for self-harm. Shared risk factors included having a lifetime psychiatric disorder, not being in paid employment, higher pandemic worry scores, and being racially minoritized. Conversely, infection with SARS-CoV-2/illness with COVID-19 was linked to lower odds of binge eating, low weight, and suicidal and/or self-harm ideation.

DISCUSSION

Overall, we detected shared risk factors that may drive the comorbidity between eating disorders and self-harm. Subgroups of individuals with these risk factors may require more frequent monitoring during future pandemics.

PUBLIC SIGNIFICANCE

In a sample of 35,000 UK residents, people who had a psychiatric disorder, identified as being part of a racially minoritized group, were not in paid employment, or were more worried about the pandemic were more likely to experience binge eating, low weight, suicidal and/or self-harm ideation, and self-harm for the first time during the pandemic. People with these risk factors may need particular attention during future pandemics to enable early identification of new psychiatric symptoms.

Patient characteristics associated with retrospectively self-reported treatment outcomes following psychological therapy for anxiety or depressive disorders - a cohort of GLAD study participants

BACKGROUND

Progress towards stratified care for anxiety and depression will require the identification of new predictors. We collected data on retrospectively self-reported therapeutic outcomes in adults who received psychological therapy in the UK in the past ten years. We aimed to replicate factors associated with traditional treatment outcome measures from the literature.

METHODS

Participants were from the Genetic Links to Anxiety and Depression (GLAD) Study, a UK-based volunteer cohort study. We investigated associations between retrospectively self-reported outcomes following therapy, on a five-point scale (global rating of change; GRC) and a range of sociodemographic, clinical and therapy-related factors, using ordinal logistic regression models (n = 2890).

RESULTS

Four factors were associated with therapy outcomes (adjusted odds ratios, OR). One sociodemographic factor, having university-level education, was associated with favourable outcomes (OR = 1.37, 95%CI: 1.18, 1.59). Two clinical factors, greater number of reported episodes of illness (OR = 0.95, 95%CI: 0.92, 0.97) and higher levels of personality disorder symptoms (OR = 0.89, 95%CI: 0.87, 0.91), were associated with less favourable outcomes. Finally, reported regular use of additional therapeutic activities was associated with favourable outcomes (OR = 1.39, 95%CI: 1.19, 1.63). There were no statistically significant differences between fully adjusted multivariable and unadjusted univariable odds ratios.

CONCLUSION

Therapy outcome data can be collected quickly and inexpensively using retrospectively self-reported measures in large observational cohorts. Retrospectively self-reported therapy outcomes were associated with four factors previously reported in the literature. Similar data collected in larger observational cohorts may enable detection of novel associations with therapy outcomes, to generate new hypotheses, which can be followed up in prospective studies.

Common Genetic Variation and Age of Onset of Anorexia Nervosa

Background

Genetics and biology may influence the age of onset of anorexia nervosa (AN). The aims of this study were to determine whether common genetic variation contributes to age of onset of AN and to investigate the genetic associations between age of onset of AN and age at menarche.

Methods

A secondary analysis of the Psychiatric Genomics Consortium genome-wide association study (GWAS) of AN was performed, which included 9335 cases and 31,981 screened controls, all from European ancestries. We conducted GWASs of age of onset, early-onset AN (<13 years), and typical-onset AN, and genetic correlation, genetic risk score, and Mendelian randomization analyses.

Results

Two loci were genome-wide significant in the typical-onset AN GWAS. Heritability estimates (single nucleotide polymorphism-h 2) were 0.01-0.04 for age of onset, 0.16-0.25 for early-onset AN, and 0.17-0.25 for typical-onset AN. Early- and typical-onset AN showed distinct genetic correlation patterns with putative risk factors for AN. Specifically, early-onset AN was significantly genetically correlated with younger age at menarche, and typical-onset AN was significantly negatively genetically correlated with anthropometric traits. Genetic risk scores for age of onset and early-onset AN estimated from independent GWASs significantly predicted age of onset. Mendelian randomization analysis suggested a causal link between younger age at menarche and early-onset AN.

Conclusions

Our results provide evidence consistent with a common variant genetic basis for age of onset and implicate biological pathways regulating menarche and reproduction.

Comparison of symptom-based versus self-reported diagnostic measures of anxiety and depression disorders in the GLAD and COPING cohorts

BACKGROUND

Understanding and improving outcomes for people with anxiety or depression often requires large sample sizes. To increase participation and reduce costs, such research is typically unable to utilise "gold-standard" methods to ascertain diagnoses, instead relying on remote, self-report measures.

AIMS

Assess the comparability of remote diagnostic methods for anxiety and depression disorders commonly used in research.

METHOD

Participants from the UK-based GLAD and COPING NBR cohorts (N = 58,400) completed an online questionnaire between 2018 and 2020. Responses to detailed symptom reports were compared to DSM-5 criteria to generate symptom-based diagnoses of major depressive disorder (MDD), generalised anxiety disorder (GAD), specific phobia, social anxiety disorder, panic disorder, and agoraphobia. Participants also self-reported any prior diagnoses from health professionals, termed self-reported diagnoses. "Any anxiety" included participants with at least one anxiety disorder. Agreement was assessed by calculating accuracy, Cohen's kappa, McNemar's chi-squared, sensitivity, and specificity.

RESULTS

Agreement between diagnoses was moderate for MDD, any anxiety, and GAD, but varied by cohort. Agreement was slight to fair for the phobic disorders. Many participants with self-reported GAD did not receive a symptom-based diagnosis. In contrast, symptom-based diagnoses of the phobic disorders were more common than self-reported diagnoses.

CONCLUSIONS

Agreement for MDD, any anxiety, and GAD was higher for cases in the case-enriched GLAD cohort and for controls in the general population COPING NBR cohort. For anxiety disorders, self-reported diagnoses classified most participants as having GAD, whereas symptom-based diagnoses distributed participants more evenly across the anxiety disorders. Further validation against gold standard measures is required.

Comparison of depression and anxiety symptom networks in reporters and non-reporters of lifetime trauma in two samples of differing severity

BACKGROUND

Reported trauma is associated with differences in the course and outcomes of depression and anxiety. However, no research has explored the association between reported trauma and patterns of clinically relevant symptoms of both depression and anxiety.

METHODS

We used network analysis to investigate associations between reported trauma and depression and anxiety symptom interactions in affected individuals from the Genetic Links to Anxiety and Depression (GLAD) Study (n = 17720), and population volunteers from the UK Biobank (n = 11120). Participants with current moderate symptoms of depression or anxiety were grouped into reporters and non-reporters of lifetime trauma. Networks of 16 depression and anxiety symptoms in the two groups were compared using the network comparison test.

RESULTS

In the GLAD Study, networks of reporters and non-reporters of lifetime trauma did not differ on any metric. In the UK Biobank, the symptom network of reporters had significantly greater density (7.80) than the network of non-reporters (7.05).

LIMITATIONS

The data collected in the GLAD Study and the UK Biobank are self-reported with validated or semi-validated questionnaires.

CONCLUSIONS

Reported lifetime trauma was associated with stronger interactions between symptoms of depression and anxiety in population volunteers. Differences between reporters and non-reporters may not be observed in individuals with severe depression and/or anxiety due to limited variance in the presentation of disorder.

Age and sex-related variability in the presentation of generalized anxiety and depression symptoms

BACKGROUND

Generalized anxiety and depression are extremely prevalent and debilitating. There is evidence for age and sex variability in symptoms of depression, but despite comorbidity it is unclear whether this extends to anxiety symptomatology. Studies using questionnaire sum scores typically fail to address this phenotypic complexity.

METHOD

We conducted exploratory and confirmatory factor analyses on Generalized Anxiety Disorder (GAD-7) and Patient Health Questionnaire (PHQ-9) items to identify latent factors of anxiety and depression in participants from the Genetic Links to Anxiety and Depression Study (N = 35,637; 16-93 years). We assessed age- and sex-related variability in latent factors and individual symptoms using multiple logistic regression.

RESULTS

Four factors of mood, worry, motor, and somatic symptoms were identified (comparative fit index [CFI] = 0.99, Tucker-Lewis Index [TLI] = 0.99, root mean square error of approximation [RMSEA] = 0.07, standardized root mean square residuals [SRMR] = 0.04). Symptoms of irritability (odds ratio [OR] = 0.81) were most strongly associated with younger age, and sleep change (OR = 1.14) with older age. Males were more likely to report mood and motor symptoms (p < .001) and females to report somatic symptoms (p < .001).

CONCLUSION

Significant age and sex variability suggest that classic diagnostic criteria reflect the presentation most commonly seen in younger males. This study provides avenues for diagnostic adaptation and factor-specific interventions.

Gaslighting in alleged assault ascertained as Munchausen syndrome transcending to malingering in highly counterintuitive self inflicted acid burns

A factitious disorder leading to the self-infliction of highly counter-intuitive burns was diagnosed in a middle-aged female. The injuries were otherwise alleged to have been sustained by assault inflicted upon her by an unknown person. The case was diagnosed by medico-legal interpretation of injuries, in spite of a highly deceptive and concocted history by the patient and her husband. The entity was unique in being associated with magnificent primary, secondary and tertiary gains. The exploitation of the morbid sequel to malinger by the patient, and the involvement of the husband for the prolongation of the illness of his wife for financial gains as gaslighting was highly unusual. The self-infliction of injuries over hands is seen in factitious disorder. However, a combination of a guarded self-immersion of the hands and feet in a corrosive by an illiterate female, followed by malingering to earn livelihood is unprecedented in factitious disorders. The delayed presentation which required amputation of all the limbs to save the life of the patient is a glaring highlight of this case.

Assessing the Role of Long Noncoding RNA in Nucleus Accumbens in Subjects With Alcohol Dependence

BACKGROUND

Long noncoding RNA (lncRNA) have been implicated in the etiology of alcohol use. Since lncRNA provide another layer of complexity to the transcriptome, assessing their expression in the brain is the first critical step toward understanding lncRNA functions in alcohol use and addiction. Thus, we sought to profile lncRNA expression in the nucleus accumbens (NAc) in a large postmortem alcohol brain sample.

METHODS

LncRNA and protein-coding gene (PCG) expressions in the NAc from 41 subjects with alcohol dependence (AD) and 41 controls were assessed via a regression model. Weighted gene coexpression network analysis was used to identify lncRNA and PCG networks (i.e., modules) significantly correlated with AD. Within the significant modules, key network genes (i.e., hubs) were also identified. The lncRNA and PCG hubs were correlated via Pearson correlations to elucidate the potential biological functions of lncRNA. The lncRNA and PCG hubs were further integrated with GWAS data to identify expression quantitative trait loci (eQTL).

RESULTS

At Bonferroni adj. p-value ≤ 0.05, we identified 19 lncRNA and 5 PCG significant modules, which were enriched for neuronal and immune-related processes. In these modules, we further identified 86 and 315 PCG and lncRNA hubs, respectively. At false discovery rate (FDR) of 10%, the correlation analyses between the lncRNA and PCG hubs revealed 3,125 positive and 1,860 negative correlations. Integration of hubs with genotype data identified 243 eQTLs affecting the expression of 39 and 204 PCG and lncRNA hubs, respectively.

CONCLUSIONS

Our study identified lncRNA and gene networks significantly associated with AD in the NAc, coordinated lncRNA and mRNA coexpression changes, highlighting potentially regulatory functions for the lncRNA, and our genetic (cis-eQTL) analysis provides novel insights into the etiological mechanisms of AD.

The Genetic Links to Anxiety and Depression (GLAD) Study: Online recruitment into the largest recontactable study of depression and anxiety

BACKGROUND

Anxiety and depression are common, debilitating and costly. These disorders are influenced by multiple risk factors, from genes to psychological vulnerabilities and environmental stressors, but research is hampered by a lack of sufficiently large comprehensive studies. We are recruiting 40,000 individuals with lifetime depression or anxiety and broad assessment of risks to facilitate future research.

METHODS

The Genetic Links to Anxiety and Depression (GLAD) Study (www.gladstudy.org.uk) recruits individuals with depression or anxiety into the NIHR Mental Health BioResource. Participants invited to join the study (via media campaigns) provide demographic, environmental and genetic data, and consent for medical record linkage and recontact.

RESULTS

Online recruitment was effective; 42,531 participants consented and 27,776 completed the questionnaire by end of July 2019. Participants' questionnaire data identified very high rates of recurrent depression, severe anxiety, and comorbidity. Participants reported high rates of treatment receipt. The age profile of the sample is biased toward young adults, with higher recruitment of females and the more educated, especially at younger ages.

DISCUSSION

This paper describes the study methodology and descriptive data for GLAD, which represents a large, recontactable resource that will enable future research into risks, outcomes, and treatment for anxiety and depression.

Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa

Characterized primarily by a low body-mass index, anorexia nervosa is a complex and serious illness1, affecting 0.9-4% of women and 0.3% of men2-4, with twin-based heritability estimates of 50-60%5. Mortality rates are higher than those in other psychiatric disorders6, and outcomes are unacceptably poor7. Here we combine data from the Anorexia Nervosa Genetics Initiative (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED) and conduct a genome-wide association study of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight significant loci. The genetic architecture of anorexia nervosa mirrors its clinical presentation, showing significant genetic correlations with psychiatric disorders, physical activity, and metabolic (including glycemic), lipid and anthropometric traits, independent of the effects of common variants associated with body-mass index. These results further encourage a reconceptualization of anorexia nervosa as a metabo-psychiatric disorder. Elucidating the metabolic component is a critical direction for future research, and paying attention to both psychiatric and metabolic components may be key to improving outcomes.

A neurobiological pathway to smoking in adolescence: TTC12-ANKK1-DRD2 variants and reward response

The TTC12-ANKK1-DRD2 gene-cluster has been implicated in adult smoking. Here, we investigated the contribution of individual genes in the TTC12-ANKK1-DRD2 cluster in smoking and their association with smoking-associated reward processing in adolescence. A meta-analysis of TTC12-ANKK1-DRD2 variants and self-reported smoking behaviours was performed in four European adolescent cohorts (N = 14,084). The minor G-allele of rs2236709, mapping TTC12, was associated with self-reported smoking (p = 5.0 × 10^-4) and higher plasma cotinine levels (p = 7.0 × 10^-5). This risk allele was linked to an increased ventral-striatal blood-oxygen level-dependent (BOLD) response during reward anticipation (n = 1,263) and with higher DRD2 gene expression in the striatum (p = 0.013), but not with TTC12 or ANKK gene expression. These data suggest a role for the TTC12-ANKK1-DRD2 gene-cluster in adolescent smoking behaviours, provide evidence for the involvement of DRD2 in the early stages of addiction and support the notion that genetically-driven inter-individual differences in dopaminergic transmission mediate reward sensitivity and risk to smoking.

Investigation of common, low-frequency and rare genome-wide variation in anorexia nervosa

Anorexia nervosa (AN) is a complex neuropsychiatric disorder presenting with dangerously low body weight, and a deep and persistent fear of gaining weight. To date, only one genome-wide significant locus associated with AN has been identified. We performed an exome-chip based genome-wide association studies (GWAS) in 2158 cases from nine populations of European origin and 15 485 ancestrally matched controls. Unlike previous studies, this GWAS also probed association in low-frequency and rare variants. Sixteen independent variants were taken forward for in silico and de novo replication (11 common and 5 rare). No findings reached genome-wide significance. Two notable common variants were identified: rs10791286, an intronic variant in OPCML (P=9.89 × 10-6), and rs7700147, an intergenic variant (P=2.93 × 10-5). No low-frequency variant associations were identified at genome-wide significance, although the study was well-powered to detect low-frequency variants with large effect sizes, suggesting that there may be no AN loci in this genomic search space with large effect sizes.

Structural effects of intra-articular TGF-β1 in moderate to advanced knee osteoarthritis: MRI-based assessment in a randomized controlled trial

BACKGROUND

To determine effects of allogeneic human chondrocytes expressing TGF-β1 (TG-C) on structural progression of MRI features of knee osteoarthritis over a 1 year period.

METHODS

This phase II randomized controlled trial of TG-C included patients with moderate to advanced osteoarthritis. Patients were randomized to receive an intraarticular 3:1 mixture of non-transduced allogeneic human chondrocytes and TG-C or placebo. 3 T MRI was acquired for all patients at baseline and follow-up (3, 6 and 12 months). MRIs were assessed using the WORMS system including cartilage damage, bone marrow lesions (BMLs), meniscal damage/extrusion, Hoffa-, effusion-synovitis, and osteophytes. Analyses were performed on a whole knee level, compartmental level, and subregional level. Binary logistic regression with Generalized Estimating Equation was used to compare risks of progression, adjusting for baseline age and gender. Mann - Whitney - Wilcoxon tests were used to assess differences for continuous variables.

RESULTS

Fifty-seven Patients were included in the TG-C group and 29 in the placebo group. At 12 months, knees in the TG-C group showed less progression of cartilage damage compared to placebo on a whole knee level (34.6% vs. 47.9%; adjusted RR 0.7, 95%CI [0.5-1.1], p = 0.077). Less progression of Hoffa-synovitis and effusion-synovitis was observed in the TG-C group compared to placebo (9.6% vs. 21.1%, adjusted RR 0.5, 95%CI [0.2,1.2], p = 0.115). No statistically significant differences were seen for BMLs, meniscal damage and osteophytes.

CONCLUSIONS

Intraarticular treatment with TG-C showed fewer patients in the treated group with progression in structural OA features and other MRI-defined inflammatory markers such as Hoffa-synovitis and effusion-synovitis. However, no differences were observed in regard to progression of BMLs and meniscal damage, or hypertrophic osteophyte formation.

TRIAL REGISTRATION

NCT01221441 .Registered 13th October, 2010.

Significant Locus and Metabolic Genetic Correlations Revealed in Genome-Wide Association Study of Anorexia Nervosa

OBJECTIVE

The authors conducted a genome-wide association study of anorexia nervosa and calculated genetic correlations with a series of psychiatric, educational, and metabolic phenotypes.

METHOD

Following uniform quality control and imputation procedures using the 1000 Genomes Project (phase 3) in 12 case-control cohorts comprising 3,495 anorexia nervosa cases and 10,982 controls, the authors performed standard association analysis followed by a meta-analysis across cohorts. Linkage disequilibrium score regression was used to calculate genome-wide common variant heritability (single-nucleotide polymorphism [SNP]-based heritability [h²_SNP]), partitioned heritability, and genetic correlations (r_g) between anorexia nervosa and 159 other phenotypes.

RESULTS

Results were obtained for 10,641,224 SNPs and insertion-deletion variants with minor allele frequencies >1% and imputation quality scores >0.6. The h²_SNP of anorexia nervosa was 0.20 (SE=0.02), suggesting that a substantial fraction of the twin-based heritability arises from common genetic variation. The authors identified one genome-wide significant locus on chromosome 12 (rs4622308) in a region harboring a previously reported type 1 diabetes and autoimmune disorder locus. Significant positive genetic correlations were observed between anorexia nervosa and schizophrenia, neuroticism, educational attainment, and high-density lipoprotein cholesterol, and significant negative genetic correlations were observed between anorexia nervosa and body mass index, insulin, glucose, and lipid phenotypes.

CONCLUSIONS

Anorexia nervosa is a complex heritable phenotype for which this study has uncovered the first genome-wide significant locus. Anorexia nervosa also has large and significant genetic correlations with both psychiatric phenotypes and metabolic traits. The study results encourage a reconceptualization of this frequently lethal disorder as one with both psychiatric and metabolic etiology.

Genome-Wide Association of Heroin Dependence in Han Chinese

Drug addiction is a costly and recurring healthcare problem, necessitating a need to understand risk factors and mechanisms of addiction, and to identify new biomarkers. To date, genome-wide association studies (GWAS) for heroin addiction have been limited; moreover they have been restricted to examining samples of European and African-American origin due to difficulty of recruiting samples from other populations. This is the first study to test a Han Chinese population; we performed a GWAS on a homogeneous sample of 370 Han Chinese subjects diagnosed with heroin dependence using the DSM-IV criteria and 134 ethnically matched controls. Analysis using the diagnostic criteria of heroin dependence yielded suggestive evidence for association between variants in the genes CCDC42 (coiled coil domain 42; p = 2.8x10^-7) and BRSK2 (BR serine/threonine 2; p = 4.110⁻⁶). In addition, we found evidence for risk variants within the ARHGEF10 (Rho guanine nucleotide exchange factor 10) gene on chromosome 8 and variants in a region on chromosome 20q13, which is gene-poor but has a concentration of mRNAs and predicted miRNAs. Gene-based association analysis identified genome-wide significant association between variants in CCDC42 and heroin addiction. Additionally, when we investigated shared risk variants between heroin addiction and risk of other addiction-related and psychiatric phenotypes using polygenic risk scores, we found a suggestive relationship with variants predicting tobacco addiction, and a significant relationship with variants predicting schizophrenia. Our genome wide association study of heroin dependence provides data in a novel sample, with functionally plausible results and evidence of genetic data of value to the field.

Gastrocnemius muscle-tendon interaction during walking in typically-developing adults and children, and in children with spastic cerebral palsy

BACKGROUND

Our understanding of the interaction of muscle bellies and their tendons in individuals with muscle pathology is limited. Knowledge of these interactions may inform us of the effects of musculoskeletal pathologies on muscle-tendon dynamics and the subsequent neurological control strategies used in gait. Here, we investigate gastrocnemius muscle-tendon interaction in typically-developing (TD) adults and children, and in children with spastic cerebral palsy (SCP).

METHODS

We recruited six TD adults (4 female; mean age: 34 yrs. (24-54)), eight TD children (5 female; mean age: 10 yrs. (6-12)) and eight independently ambulant children with SCP (5 female; mean age 9 yrs. (6-12); 3 unilaterally-affected). A combination of 3D motion capture and 2D real-time ultrasound imaging were used to compute the gastrocnemius musculo-tendinous unit (MTU) length and estimate muscle belly and tendon lengths during walking. For the TD subjects, the measurements were made for heel-toe walking and voluntary toe-walking.

RESULTS

The gastrocnemius muscle bellies of children with SCP lengthened during single support (p = 0.003). In contrast, the muscle bellies of TD subjects did not demonstrate an increase in length over the period of single support under heel-toe or toe-walking conditions.

CONCLUSION

We observed lengthening of the gastrocnemius muscle bellies in children with SCP during single support, a phase of the gait cycle in which the muscle is reported consistently to be active. Repeated lengthening of muscle bellies while they are active may lead to muscle damage and have implications for the natural history of gait in this group.

Integrating mRNA and miRNA Weighted Gene Co-Expression Networks with eQTLs in the Nucleus Accumbens of Subjects with Alcohol Dependence

Alcohol consumption is known to lead to gene expression changes in the brain. After performing weighted gene co-expression network analyses (WGCNA) on genome-wide mRNA and microRNA (miRNA) expression in Nucleus Accumbens (NAc) of subjects with alcohol dependence (AD; N = 18) and of matched controls (N = 18), six mRNA and three miRNA modules significantly correlated with AD were identified (Bonferoni-adj. p≤ 0.05). Cell-type-specific transcriptome analyses revealed two of the mRNA modules to be enriched for neuronal specific marker genes and downregulated in AD, whereas the remaining four mRNA modules were enriched for astrocyte and microglial specific marker genes and upregulated in AD. Gene set enrichment analysis demonstrated that neuronal specific modules were enriched for genes involved in oxidative phosphorylation, mitochondrial dysfunction and MAPK signaling. Glial-specific modules were predominantly enriched for genes involved in processes related to immune functions, i.e. cytokine signaling (all adj. p≤ 0.05). In mRNA and miRNA modules, 461 and 25 candidate hub genes were identified, respectively. In contrast to the expected biological functions of miRNAs, correlation analyses between mRNA and miRNA hub genes revealed a higher number of positive than negative correlations (χ² test p≤ 0.0001). Integration of hub gene expression with genome-wide genotypic data resulted in 591 mRNA cis-eQTLs and 62 miRNA cis-eQTLs. mRNA cis-eQTLs were significantly enriched for AD diagnosis and AD symptom counts (adj. p = 0.014 and p = 0.024, respectively) in AD GWAS signals in a large, independent genetic sample from the Collaborative Study on Genetics of Alcohol (COGA). In conclusion, our study identified putative gene network hubs coordinating mRNA and miRNA co-expression changes in the NAc of AD subjects, and our genetic (cis-eQTL) analysis provides novel insights into the etiological mechanisms of AD.

A genome-wide association study of anorexia nervosa

Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome-wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2907 cases with AN from 14 countries (15 sites) and 14 860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery data sets. Seventy-six (72 independent) single nucleotide polymorphisms were taken forward for in silico (two data sets) or de novo (13 data sets) replication genotyping in 2677 independent AN cases and 8629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication data sets comprised 5551 AN cases and 21 080 controls. AN subtype analyses (1606 AN restricting; 1445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01 × 10(-7)) in SOX2OT and rs17030795 (P=5.84 × 10(-6)) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76 × 10(-)(6)) between CUL3 and FAM124B and rs1886797 (P=8.05 × 10(-)(6)) near SPATA13. Comparing discovery with replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P=4 × 10(-6)), strongly suggesting that true findings exist but our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field.

Genomewide association analysis of symptoms of alcohol dependence in the molecular genetics of schizophrenia (MGS2) control sample

BACKGROUND

While genetic influences on alcohol dependence (AD) are substantial, progress in the identification of individual genetic variants that impact on risk has been difficult.

METHODS

We performed a genome-wide association study on 3,169 alcohol consuming subjects from the population-based Molecular Genetics of Schizophrenia (MGS2) control sample. Subjects were asked 7 questions about symptoms of AD which were analyzed by confirmatory factor analysis. Genotyping was performed using the Affymetrix 6.0 array. Three sets of analyses were conducted separately for European American (EA, n = 2,357) and African-American (AA, n = 812) subjects: individual single nucleotide polymorphisms (SNPs), candidate genes and enriched pathways using gene ontology (GO) categories.

RESULTS

The symptoms of AD formed a highly coherent single factor. No SNP approached genome-wide significance. In the EA sample, the most significant intragenic SNP was in KCNMA1, the human homolog of the slo-1 gene in C. Elegans. Genes with clusters of significant SNPs included AKAP9, phosphatidylinositol glycan anchor biosynthesis, class G (PIGG), and KCNMA1. In the AA sample, the most significant intragenic SNP was CEACAM6 and genes showing empirically significant SNPs included KCNQ5, SLC35B4, and MGLL. In the candidate gene based analyses, the most significant findings were with ADH1C, nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (NFKB1) and ankyrin repeat and kinase domain containing 1 (ANKK1) in the EA sample, and ADH5, POMC, and CHRM2 in the AA sample. The ALIGATOR program identified a significant excess of associated SNPs within and near genes in a substantial number of GO categories over a range of statistical stringencies in both the EA and AA sample.

CONCLUSIONS

While we cannot be highly confident about any single result from these analyses, a number of findings were suggestive and worthy of follow-up. Although quite large samples will be needed to obtain requisite power, the study of AD symptoms in general population samples is a viable complement to case-control studies in identifying genetic risk variants for AD.

Neurotransmitter and neuromodulator genes associated with a history of depressive symptoms in individuals with alcohol dependence

BACKGROUND

Depressive symptoms are common among individuals with alcohol use disorders and impact treatment outcome. Substantial overlap exists among the neurobiological systems proposed in the pathophysiology of depressive and alcohol use disorders; however, specific genetic effects contributing to risk for depressive comorbidity remain poorly understood.

METHODS

This study examines the association of depressive symptom scores for lifetime depression (the sum of DSM-IV major depression co-endorsed criteria for lifetime depression) with markers in 120 candidate genes in 554 alcohol-dependent individuals. The candidate genes code for molecules involved in dopamine, serotonin, glutamate, gamma-aminobutyric acid (GABA), and opioid neurotransmission, cell signaling, pharmacokinetics, stress biology, and behavioral control. Analyses were conducted at the single marker level with experimentwise permutation to control for multiple testing.

RESULTS

Results revealed nominal associations for markers in 20 genes. Following experimentwise permutation, markers in the corticotropin-releasing hormone-binding protein (CRHBP) the μ-opioid receptor (OPRM1) and the β1 subunit of GABA A (GABA(A)) receptors (GABRB1) met or exceeded the significance threshold. None of the markers associated with depressive symptom scores were significantly associated with alcohol dependence symptom scores.

CONCLUSION

These findings suggest potential risk genes for depressive symptoms in alcohol-dependent individuals.

Limited associations of dopamine system genes with alcohol dependence and related traits in the Irish Affected Sib Pair Study of Alcohol Dependence (IASPSAD)

BACKGROUND

Over 50 years of evidence from research has established that the central dopaminergic reward pathway is likely involved in alcohol dependence (AD). Additional evidence supports a role for dopamine (DA) in other disinhibitory psychopathology, which is often comorbid with AD. Family and twin studies demonstrate that a common genetic component accounts for most of the genetic variance in these traits. Thus, DA-related genes represent putative candidates for the genetic risk that underlies not only AD but also behavioral disinhibition. Many linkage and association studies have examined these relationships with inconsistent results, possibly because of low power, poor marker coverage, and/or an inappropriate correction for multiple testing.

METHODS

We conducted an association study on the products encoded by 10 DA-related genes (DRD1-D5, SLC18A2, SLC6A3, DDC, TH, COMT) using a large, ethnically homogeneous sample with severe AD (n = 545) and screened controls (n = 509). We collected genotypes from linkage disequilibrium (LD)-tagging single nucleotide polymorphisms (SNPs) and employed a gene-based method of correction. We tested for association with AD diagnosis in cases and controls and with a variety of alcohol-related traits (including age-at-onset, initial sensitivity, tolerance, maximum daily drinks, and a withdrawal factor score), disinhibitory symptoms, and a disinhibitory factor score in cases only. A total of 135 SNPs were genotyped using the Illumina GoldenGate and Taqman Assays-on-Demand protocols.

RESULTS

Of the 101 SNPs entered into standard analysis, 6 independent SNPs from 5 DA genes were associated with AD or a quantitative alcohol-related trait. Two SNPs across 2 genes were associated with a disinhibitory symptom count, while 1 SNP in DRD5 was positive for association with the general disinhibitory factor score.

CONCLUSIONS

Our study provides evidence of modest associations between a small number of DA-related genes and AD as well as a range of alcohol-related traits and measures of behavioral disinhibition. While we did conduct gene-based correction for multiple testing, we did not correct for multiple traits because the traits are correlated. However, false-positive findings remain possible, so our results must be interpreted with caution.

A threonine to isoleucine missense mutation in the pericentriolar material 1 gene is strongly associated with schizophrenia

Markers at the pericentriolar material 1 gene (PCM1) have shown genetic association with schizophrenia in both a University College London (UCL) and a USA-based case-control sample. In this paper we report a statistically significant replication of the PCM1 association in a large Scottish case-control sample from Aberdeen. Resequencing of the genomic DNA from research volunteers who had inherited haplotypes associated with schizophrenia showed a threonine to isoleucine missense mutation in exon 24 which was likely to change the structure and function of PCM1 (rs370429). This mutation was found only as a heterozygote in 98 schizophrenic research subjects and controls out of 2246 case and control research subjects. Among the 98 carriers of rs370429, 67 were affected with schizophrenia. The same alleles and haplotypes were associated with schizophrenia in both the London and Aberdeen samples. Another potential aetiological base pair change in PCM1 was rs445422, which altered a splice site signal. A further mutation, rs208747, was shown by electrophoretic mobility shift assays to create or destroy a promoter transcription factor site. Five further non-synonymous changes in exons were also found. Genotyping of the new variants discovered in the UCL case-control sample strengthened the evidence for allelic and haplotypic association (P=0.02-0.0002). Given the number and identity of the haplotypes associated with schizophrenia, further aetiological base pair changes must exist within and around the PCM1 gene. PCM1 protein has been shown to interact directly with the disrupted-in-schizophrenia 1 (DISC1) protein, Bardet-Biedl syndrome 4, and Huntingtin-associated protein 1, and is important in neuronal cell growth. In a separate study we found that clozapine but not haloperidol downregulated PCM1 expression in the mouse brain. We hypothesize that mutant PCM1 may be responsible for causing a subtype of schizophrenia through abnormal cell division and abnormal regeneration in dividing cells in the central nervous system. This is supported by our previous finding of orbitofrontal volumetric deficits in PCM1-associated schizophrenia patients as opposed to temporal pole deficits in non-PCM1-associated schizophrenia patients. Caution needs to be exercised in interpreting the actual biological effects of the mutations we have found without further cell biology. However, the DNA changes we have found deserve widespread genotyping in multiple case-control populations.

A systematic gene-based screen of chr4q22-q32 identifies association of a novel susceptibility gene, DKK2, with the quantitative trait of alcohol dependence symptom counts

Studies of alcohol dependence (AD) have consistently found evidence of linkage on chromosome 4q21-q32. A genome-wide linkage scan in the Irish Affected Sib Pair Study of Alcohol Dependence (IASPSAD) sample also provided its strongest evidence of linkage on chromosome 4q22-q32 using an index of AD severity based on the count of DSM-IV AD symptoms (ADSX; LOD = 4.59). We conducted a systematic, gene-centric association study using 518 LD-tagging single nucleotide polymorphisms (SNPs) in the 65 known and predicted genes within the 1-LOD interval surrounding the linkage peak. Case-only regression analysis with the quantitative variable of ADSX was performed in the 562 genetically independent cases; nominal support for association was demonstrated by 32 tagging SNPs in 14 genes. We did not observe study-wide significance, but gene-wise correction for multiple testing with the Nyholt procedure yielded empirical evidence of association with two genes, DKK2 (dickkopf homolog 2) (P = 0.007) and EGF (epidermal growth factor) (P = 0.025) in the IASPSAD sample. Three SNPs in DKK2 (rs427983; rs419558; rs399087) demonstrated empirical significance. Assessment of possible replication in 847 cases of European descent from a large independent sample, the Collaborative Study of the Genetics of Alcoholism, yielded replication for DKK2 but not EGF. We observed genotypic and phenotypic replication for DKK2 with the three SNPs yielding significant association with ADSX in the IASPSAD sample. Haplotype-specific expression measurements in post-mortem tissue samples suggested a functional role for DKK2. This evidence notwithstanding, replication is needed before confidence can be placed in these findings.

Associations of glutamate decarboxylase genes with initial sensitivity and age-at-onset of alcohol dependence in the Irish Affected Sib Pair Study of Alcohol Dependence

BACKGROUND

The relation of gamma-aminobutyric acid (GABA) to alcohol dependence (AD) has been widely studied. Several previous studies suggest that GABA may be involved in alcohol withdrawal, tolerance, and the symptoms that form an AD diagnosis. The genes coding for glutamate decarboxylase (GAD), the rate-limiting enzyme in GABA synthesis, are of potential interest for their association to ethanol consumption and AD. There are two isoforms of GAD, GAD1 and GAD2, which were reported to be associated with AD in males of Han Taiwanese (GAD1) and Russian (GAD2) ancestry. The present study examined the association of the two GAD isoforms with AD and relevant alcohol-related traits in the Irish Affected Sib Pair Study of Alcohol Dependence [Prescott, C.A., Sullivan, P.F., Myers, J.M., Patterson, D.G., Devitt, M., Halberstadt, L.J., Walsh, D., Kendler, K.S., 2005. The Irish Affected Sib Pair Study of Alcohol Dependence: study methodology and validation of diagnosis by interview and family history. Alcohol.-Clin. Exp. Res. 29 (3) 417-429].

METHODS

Participants were recruited in Ireland, including 575 independent cases who met DSM-IV AD criteria and 530 controls, screened for heavy drinking. We first conducted case-control analyses of the GAD genes with AD and, within the cases, examined associations with age at onset of AD, withdrawal symptoms, and two quantitative measures: initial sensitivity and tolerance (based on scales from the Self-Rating of the Effects of Ethanol) [Schuckit, M.A., Smith, T.L., Tipp, J.E., 1997. The self-rating of the effects of alcohol (SRE) form as a retrospective measure of the risk for alcoholism. Addiction 92, 979-988]. A total of 29 SNPs were genotyped for GAD1 and GAD2 using the Illumina GoldenGate protocols. Statistical procedures were implemented to control for false discovery rates (FDR).

RESULTS

Nine of 29 markers with minor allele frequencies less than 0.01 were removed from standard analysis; the remaining 20 markers were all in Hardy-Weinberg equilibrium. Three markers in the intronic regions of GAD1 were associated with initial sensitivity to alcohol (P=0.002); the associations remained significant after a FDR based correction for multiple testing. In addition, one marker located 3kb upstream of GAD1 exhibited association with age at onset of AD (P=0.0001). Gender specific effects were observed in results of both single marker and haplotype analyses.

CONCLUSION

We found no evidence for the association of GAD genes with AD but significant association of GAD1 with initial sensitivity and age at onset of AD. Our findings suggest that the underlying pathophysiology regulated by genes like GAD1 may be more directly related to the component processes that form AD than to the clinical disorder.

Association of ADH and ALDH genes with alcohol dependence in the Irish Affected Sib Pair Study of alcohol dependence (IASPSAD) sample

BACKGROUND

The genes coding for ethanol metabolism enzymes [alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH)] have been widely studied for their influence on the risk to develop alcohol dependence (AD). However, the relation between polymorphisms of these metabolism genes and AD in Caucasian subjects has not been clearly established. The present study examined evidence for the association of alcohol metabolism genes with AD in the Irish Affected Sib Pair Study of alcohol dependence.

METHODS

We conducted a case-control association study with 575 independent subjects who met Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, AD diagnosis and 530 controls. A total of 77 single nucleotide polymorphisms (SNPs) in the seven ADH (ADH1-7) and two ALDH genes (ALDH1A1 and ALDH2) were genotyped using the Illumina GoldenGate protocols. Several statistical procedures were implemented to control for false discoveries.

RESULTS

All markers with minor allele frequency greater than 0.01 were in Hardy-Weinberg equilibrium. Numerous SNPs in ADH genes showed association with AD, including one marker in the coding region of ADH1C (rs1693482 in exon6, Ile271Gln). Haplotypic association was observed in the ADH5 and ADH1C genes, and in a long haplotype block formed by the ADH1A and ADH1B loci. We detected two significant interactions between pairs of markers in intron 6 of ADH6 and intron 12 of ALDH2 (p = 5 x 10(-5)), and 5' of both ADH4 and ADH1A (p = 2 x 10(-4)).

CONCLUSION

We found evidence for the association of several ADH genes with AD in a sample of Western European origin. The significant interaction effects between markers in ADH and ALDH genes suggest possible epistatic roles between alcohol metabolic enzymes in the risk for AD.

Alcohol dependence is associated with the ZNF699 gene, a human locus related to Drosophila hangover, in the Irish Affected Sib Pair Study of Alcohol Dependence (IASPSAD) sample

Because tolerance is an important aspect of alcohol dependence (AD) in humans, recent evidence showing that the Drosophila gene hang is critically involved in the development of alcohol tolerance in the fly suggests that variation in related human loci might be important in the etiology of alcohol-related disorders. The orthology of hang in mammals is complex, but a number of human gene products (including ZNF699) with similar levels of amino-acid identity (18-26%) and similarity (30-41%), are consistently identified as the best matches with the translated hang sequence. We tested for association between the dichotomous clinical phenotype of alcohol dependence and seven single nucleotide polymorphisms (SNPs) in ZNF699 in our sample of 565 genetically independent cases and 496 siblings diagnosed with AD, and 609 controls. In analyses of genetically independent cases and controls, four of the seven single markers show strong evidence for association with AD (0.00003<Fisher's exact P<0.001), and the most significant single marker, rs7254880, tags an associated haplotype with frequency 0.071 in cases compared to 0.034 in controls (chi2 15.563, P<0.00008, 5000 permutation P<0.001, OR 2.17); inclusion of affected siblings gives similar results. Expression analyses conducted in independent postmortem brain samples show that expression of ZNF699 mRNA is significantly reduced in the dorsolateral prefrontal cortex of individuals carrying this haplotype compared with other observed haplotype combinations.

A Joint Genomewide Linkage Analysis of Symptoms of Alcohol Dependence and Conduct Disorder

BACKGROUND

A large linkage peak for alcohol dependence (AD) was detected on chromosome 4q in the Irish Affected Sib Pair Study of Alcohol Dependence (IASPSAD). Are the susceptibility genes underlying this peak specific for AD or do they increase risk for externalizing disorders more generally? Can we, in the IASPSAD, replicate prior evidence for linkage to conduct disorder (CD)?

METHODS

The 733 all possible sibling pairs in IASPSAD were typed for 1,020 short-tandem-repeat genetic markers. Univariate and bivariate linkage analyses were conducted by the program sequential oligogenic linkage analysis routines (SOLAR), for both the raw and the transformed number of symptoms of AD (ADsx) and number of symptoms of CD (CDsx). In the bivariate analyses, specificity was assessed by the ratio of the variance accounted for in ADsx and CDsx by the quantitative trait locus.

RESULTS

In the univariate linkage analyses, no evidence for linkage to CDsx was found under the 4q peak for ADsx and the largest peaks for CDsx were seen on chromosomes 1q (LOD=3.16) and 14p (LOD=2.36). In the bivariate linkage analysis, the 4q peak had high specificity for AD (AD/CD ratio of 39.9). Several smaller peaks, on chromosomes 1, 7, and 10, had moderate specificity for CD but also impacted on risk for AD, with AD/CD ratios of 0.18 to 0.32.

CONCLUSIONS

Genes under the 4q linkage peak for AD in the IASPSAD impact specifically on risk for AD rather than more broadly on risk for externalizing syndromes. Suggestive linkages were found in several locations for CD, 2 of which broadly replicate prior findings. The bivariate analyses identified genomic locations containing susceptibility loci that impacted on risk for both CDsx and ADsx.

Identification of the Slynar gene (AY070435) and related brain expressed sequences as a candidate gene for susceptibility to affective disorders through allelic and haplotypic association with bipolar disorder on chromosome 12q24

OBJECTIVE

Three linkage studies of bipolar disorder have implicated chromosome 12q24.3, with significant lod scores of over 3.00. Several other linkage studies have found lod scores between 2.00 and 3.00. In order to identify which gene on this chromosome is responsible, the authors carried out tests of allelic association with bipolar disorder in order to fine map an affective disorder susceptibility gene.

METHOD

DNA samples from 681 bipolar disorder patients and 570 comparison subjects from Denmark and the United Kingdom were genotyped with markers close to the region at which the authors had found maximum linkage in previous studies.

RESULTS

Single marker allelic association was found with four markers in the Danish cohort. Seven markers in exactly the same region were then found to show significant allelic association in the U.K. cohort. Tests of haplotypic association were also significant, confirming the single marker allelic associations.

CONCLUSIONS

These positive fine mapping results validate earlier linkage studies and implicate a 278-kilobase region of chromosome 12 that contributes to the etiology of bipolar disorder. Several brain transcripts are transcribed from sequences in the region. The main candidate gene has no known function but is found in human brain cDNA and is homologous to a Macaque brain cDNA. Sequencing of expressed sequences and control regions in the area should identify etiological base pair changes that increase susceptibility to bipolar disorder.

Genetic association and brain morphology studies and the chromosome 8p22 pericentriolar material 1 (PCM1) gene in susceptibility to schizophrenia

CONTEXT

There is evidence of linkage to a schizophrenia susceptibility locus on chromosome 8p21-22 found by several family linkage studies.

OBJECTIVES

To fine map and identify a susceptibility gene for schizophrenia on chromosome 8p22 and to investigate the effect of this genetic susceptibility on an endophenotype of abnormal brain structure using magnetic resonance imaging.

DESIGN

Fine mapping and identification of a chromosome 8p22 susceptibility gene was carried out by finding linkage disequilibrium between genetic markers and schizophrenia in multiply affected families, a case-control sample, and a trio sample. Variation in brain morphology associated with pericentriolar material 1 (PCM1) alleles was examined using voxel-based morphometry and statistical parametric mapping with magnetic resonance imaging. Setting and Patients A family sample of 13 large families multiply affected with schizophrenia, 2 schizophrenia case-control samples from the United Kingdom and Scotland, and a sample of schizophrenic trios from the United States containing parents and 1 affected child with schizophrenia.

MAIN OUTCOME MEASURES

Tests of transmission disequilibrium between PCM1 locus polymorphisms and schizophrenia using a family sample and tests of allelic association in case-control and trio samples. Voxel-based morphometry using statistical parametric mapping.

RESULTS

The family and trio samples both showed significant transmission disequilibrium between marker D85261 in the PCM1 gene locus and schizophrenia. The case-control sample from the United Kingdom also found significant allelic association between PCM1 gene markers and schizophrenia. Voxel-based morphometry of cases who had inherited a PCM1 genetic susceptibility showed a significant relative reduction in the volume of orbitofrontal cortex gray matter in comparison with patients with non-PCM1-associated schizophrenia, who, by contrast, showed gray matter volume reduction in the temporal pole, hippocampus, and inferior temporal cortex.

CONCLUSIONS

The PCM1 gene is implicated in susceptibility to schizophrenia and is associated with orbitofrontal gray matter volumetric deficits.

Fine mapping of a susceptibility locus for bipolar and genetically related unipolar affective disorders, to a region containing the C21ORF29 and TRPM2 genes on chromosome 21q22.3

Linkage analyses of bipolar families have confirmed that there is a susceptibility locus near the telomere on chromosome 21q. To fine map this locus we carried out tests of allelic association using 30 genetic markers near the telomere at 21q22.3 in 600 bipolar research subjects and 450 ancestrally matched supernormal control subjects. We found significant allelic association with the microsatellite markers D21S171 (P=0.016) and two closely linked single-nucleotide polymorphisms, rs1556314 (P=0.008) and rs1785467 (P=0.025). A test of association with a three locus haplotype across the susceptibility region was significant with a permutation test of P=0.011. A two SNP haplotype was also significantly associated with bipolar disorder (P=0.01). Only two brain expressed genes, TRPM2 and C21ORF29 (TSPEAR), are present in the associated region. TRPM2 encodes a calcium channel receptor and TSPEAR encodes a peptide with repeats associated with epilepsy in the mouse. DNA from subjects who had inherited the associated marker alleles was sequenced. A base pair change (rs1556314) in exon 11 of TRPM2, which caused a change from an aspartic acid to a glutamic acid at peptide position 543 was found. This SNP showed the strongest association with bipolar disorder (P=0.008). Deletion of exon 11 of TRPM2 is known to cause dysregulation of cellular calcium homeostasis in response to oxidative stress. A second nonconservative change from arginine to cysteine at position 755 in TRPM2 (ss48297761) was also detected. A third nonconservative change from histidine to glutamic acid was found in exon 8 of TSPEAR. These changes need further investigation to establish any aetiological role in bipolar disorder.

The Epsin 4 gene on chromosome 5q, which encodes the clathrin-associated protein enthoprotin, is involved in the genetic susceptibility to schizophrenia

Chromosome 5q33 is a region that has previously shown good evidence of linkage to schizophrenia, with four LOD scores >3.00 in independent linkage studies. We studied 450 unrelated white English, Irish, Welsh, and Scottish research subjects with schizophrenia and 450 ancestrally matched supernormal controls. Four adjacent markers at the 5' end of the Epsin 4 gene showed significant evidence of linkage disequilibrium with schizophrenia. These included two microsatellite markers, D5S1403 (P=.01) and AAAT11 (P=.009), and two single-nucleotide-polymorphism markers within the Epsin 4 gene, rs10046055 (P=.007) and rs254664 (P=.01). A series of different two- and three-marker haplotypes were also significantly associated with schizophrenia, as confirmed with a permutation test (HapA, P=.004; HapB, P=.0005; HapC, P=.007; and HapD, P=.01). The Epsin 4 gene encodes the clathrin-associated protein enthoprotin, which has a role in transport and stability of neurotransmitter vesicles at the synapses and within neurons. A genetically determined abnormality in the structure, function, or expression of enthoprotin is likely to be responsible for genetic susceptibility to a subtype of schizophrenia on chromosome 5q33.3.

Genome scan of Tourette syndrome in a single large pedigree shows some support for linkage to regions of chromosomes 5, 10 and 13

OBJECTIVES

To localize genes influencing the susceptibility to Gilles de la Tourette syndrome (GTS) and associated chronic multiple tics (CMT).

METHOD

A single, large, multiple affected pedigree containing 35 subjects diagnosed with GTS and a further 14 with CMT was genotyped for markers spanning the autosomes. Linkage analysis was carried out using classical lod score analysis and model-free lod score analysis. All markers were subjected to two-point analysis, and markers producing a two-point result significant at P<0.005 were subjected to three-point analysis using adjacent markers.

RESULTS

The following markers produced at least one result significant at 0.005 using two-point analysis: D5S1981, D5S2050, D10S591, D10S189, D13S217, and D14S288. Three-point analysis with D5S2050 and D5S400 produced a lod of 2.9 with CMT. Three-point analysis of D10S591 and D10S189 produced lods of 1.9 with GTS and CMT. Three-point analysis of D13S217 and D13S171 produced a lod of 2.7 with GTS. No single haplotype appeared to account for the majority of cases within the pedigree.

CONCLUSIONS

It seems likely that more than one susceptibility allele is present in the pedigree. Although none of the three positive regions is conclusively implicated, it seems probable that at least one contains a susceptibility locus. We recommend that association-based studies be carried out in these three regions to produce further evidence for a localization and to carry out fine-mapping.

Genome scan meta-analysis of schizophrenia and bipolar disorder, part III: Bipolar disorder

Genome scans of bipolar disorder (BPD) have not produced consistent evidence for linkage. The rank-based genome scan meta-analysis (GSMA) method was applied to 18 BPD genome scan data sets in an effort to identify regions with significant support for linkage in the combined data. The two primary analyses considered available linkage data for "very narrow" (i.e., BP-I and schizoaffective disorder-BP) and "narrow" (i.e., adding BP-II disorder) disease models, with the ranks weighted for sample size. A "broad" model (i.e., adding recurrent major depression) and unweighted analyses were also performed. No region achieved genomewide statistical significance by several simulation-based criteria. The most significant P values (<.01) were observed on chromosomes 9p22.3-21.1 (very narrow), 10q11.21-22.1 (very narrow), and 14q24.1-32.12 (narrow). Nominally significant P values were observed in adjacent bins on chromosomes 9p and 18p-q, across all three disease models on chromosomes 14q and 18p-q, and across two models on chromosome 8q. Relatively few BPD pedigrees have been studied under narrow disease models relative to the schizophrenia GSMA data set, which produced more significant results. There was no overlap of the highest-ranked regions for the two disorders. The present results for the very narrow model are promising but suggest that more and larger data sets are needed. Alternatively, linkage might be detected in certain populations or subsets of pedigrees. The narrow and broad data sets had considerable power, according to simulation studies, but did not produce more highly significant evidence for linkage. We note that meta-analysis can sometimes provide support for linkage but cannot disprove linkage in any candidate region.

Genome scan meta-analysis of schizophrenia and bipolar disorder, part II: Schizophrenia

Schizophrenia is a common disorder with high heritability and a 10-fold increase in risk to siblings of probands. Replication has been inconsistent for reports of significant genetic linkage. To assess evidence for linkage across studies, rank-based genome scan meta-analysis (GSMA) was applied to data from 20 schizophrenia genome scans. Each marker for each scan was assigned to 1 of 120 30-cM bins, with the bins ranked by linkage scores (1 = most significant) and the ranks averaged across studies (R(avg)) and then weighted for sample size (N(sqrt)[affected casess]). A permutation test was used to compute the probability of observing, by chance, each bin's average rank (P(AvgRnk)) or of observing it for a bin with the same place (first, second, etc.) in the order of average ranks in each permutation (P(ord)). The GSMA produced significant genomewide evidence for linkage on chromosome 2q (PAvgRnk<.000417). Two aggregate criteria for linkage were also met (clusters of nominally significant P values that did not occur in 1,000 replicates of the entire data set with no linkage present): 12 consecutive bins with both P(AvgRnk) and P(ord)<.05, including regions of chromosomes 5q, 3p, 11q, 6p, 1q, 22q, 8p, 20q, and 14p, and 19 consecutive bins with P(ord)<.05, additionally including regions of chromosomes 16q, 18q, 10p, 15q, 6q, and 17q. There is greater consistency of linkage results across studies than has been previously recognized. The results suggest that some or all of these regions contain loci that increase susceptibility to schizophrenia in diverse populations.

Genome scan of pedigrees multiply affected with bipolar disorder provides further support for the presence of a susceptibility locus on chromosome 12q23-q24, and suggests the presence of additional loci on 1p and 1q

OBJECTIVE

To localize genes conferring susceptibility to bipolar affective disorder.

METHODS

Seven families were selected on the basis of containing multiple cases of bipolar affective disorder present in three or more generations, an absence of schizophrenia and unilineal transmission. DNA samples from these families were genotyped with 365 microsatellite markers spaced at approximately 10 cM intervals across the whole genome. All markers were subjected to initial two-point and three-point analyses using LOD score and model-free analysis. All regions producing a result significant at P<0.01 were then subjected to four-point LOD score analysis under the assumption of heterogeneity. RESULTSA four-point LOD score of 2.8 was obtained using a dominant model and including unipolar cases as affected in the region of D12S342. Four-point LOD scores of 2 were obtained around D1S243, D1S251 and D3S1265. The positive results around D1S243 were accounted for by a LOD score of 3.1 occurring in a single pedigree.

CONCLUSIONS

Since there has been previous strong support for linkage to the region of 12q23-q24 around D12S342, it now seems very probable that it does indeed contain a gene influencing susceptibility to bipolar affective disorder. Some evidence for linkage in the region of 1q near to D1S251 has been reported in one previous study. It therefore seems that this region of 1q and the region of 1p close to D1S243 may also harbour susceptibility genes.

Variation in the DCP1 gene, encoding the angiotensin converting enzyme ACE, is not associated with increased susceptibility to Alzheimer's disease

OBJECTIVES

To attempt to replicate previous reports that polymorphic variation in the DCP1 gene causes increased susceptibility to the development of Alzheimer's disease, either on its own or in interaction with the effects of the gene for apolipoprotein E (APOE).

METHOD

Subjects older than 65 years of age consisting of 81 dementia patients diagnosed as having possible or probable Alzheimer's disease and 68 controls were obtained from Camden, Islington and Harlow psychiatric services. Subjects were genotyped for APOE alleles e2, e3 and e4, and the common insertion/deletion polymorphisms for DCP1* I/D were genotyped.

RESULTS

There was no statistically significant difference in the frequency of the DCP1* insertion/deletion alleles between the cases and controls (X2 =0.04, 1 degree of freedom, not significant). When subjects were subdivided according to whether they possessed at least one copy of the APOE e4 allele, there were still no differences in DCP1 allele frequencies between cases and controls.

CONCLUSIONS

Further research is needed to elucidate any role that the DCP1 polymorphism may play in relation to Alzheimer's disease. Previous studies may be false positive, or inconsistency in replication may be due to heterogeneity.

A novel polymorphism in exon 11 of the WKL1 gene, shows no association with schizophrenia

A missense mutation in exon 11 of the WKL1 gene on chromosome 22 was found to be associated with cases of catatonic schizophrenia in a single large pedigree. We have screened exon 11 of the WKL1 gene in 174 cases of schizophrenia, including cases of 22 cases of catatonic schizophrenia, but could not detect the previously reported mis-sense mutation. However in exon 11, we observed an insertion/deletion polymorphism, one-missense substitution and two synonymous substitutions. In addition, we also identified a nucleotide substitution in intron 11. All these polymorphisms appeared to be in complete linkage disequilibrium with one another. The polymorphisms were also identified in a UK pedigree with schizophrenia, however the polymorphisms did not segregate with the disease. To test for potential association between these polymorphisms and schizophrenia we sequenced an equal number of UK control individuals who were free of all psychiatric symptoms and had negative family histories for mental illness; the frequency of the insertion/deletion polymorphism was not significantly different in schizophrenia cases (42 out of 348 chromosomes, allele frequency 12%) compared to normal controls (40 out of 356 chromosomes, allele frequency 11%). The insertion/deletion was found to be in Hardy Weinberg equilibrium in both the schizophrenic and control groups. The insertion/deletion is composed of repeated sequence from exon 11 and intron 11 and is predicted to affect WKL1 protein structure.

Linkage disequilibrium and demographic history of the isolated population of the Faroe Islands

The isolated population of the Faroe Islands has a history of recent expansion after being limited to a small size for centuries. Such an isolated population may be ideal for linkage disequilibrium mapping of disease genes if linkage disequilibrium (LD) extends over large regions. Analyses of 18 markers on 12q24.3, spanning a region of 4.3 Mb (16 cM), revealed extensive LD in the Faroese population. Maximum LD was found between marker pairs separated by more than 3.8 Mb. The same region had a maximum LD of only 1.2 and 1.4 Mb respectively in two outbred Danish and British populations analysed here for comparison. The analyses of gene diversity excess at 15 unlinked microsatellite markers did not reveal any sign of a severe bottleneck to have occurred within approximately 1200 years' history of the Faroese population. The extensive LD in this population may, therefore, have arisen primarily by random genetic drift. The implications for future gene mapping studies are discussed.

Genetic association studies of schizophrenia using the 8p21-22 genes: prepronociceptin (PNOC), neuronal nicotinic cholinergic receptor alpha polypeptide 2 (CHRNA2) and arylamine N-acetyltransferase 1 (NAT1)

Schizophrenia is a common, genetically heterogeneous disorder with a lifetime prevalence of approximately 1% in the general population. Linkage studies of affected families have now strongly implicated a susceptibility locus on chromosome 8p21-22. Tests of allelic association with markers on 8p21-22 should be able to localise any quantitative trait nucleotides (QTN's) or susceptibility mutations to within a few hundred kilobases. Three brain expressed candidate susceptibility genes, prepronociceptin (PNOC), neuronal cholinergic receptor, nicotinic, alpha polypeptide 2 (CHRNA2) and arylamine N-acetyltransferase 1 (NAT1) have been mapped to chromosome 8p21-22. A case-control, allelic association study was performed using a novel highly polymorphic dinucleotide repeat, D8S2611 near the PNOC gene, two previously characterised dinucleotide repeats, D8S131 and D8S131P at the CHRNA2 locus and an RFLP at the 3'UTR of the arylamine N-acetyltransferase 1 (NAT1) gene. No differences were found in allele frequencies between the patient and control groups. DNA variations or mutations at or near the three genes under study are unlikely to increase susceptibility to schizophrenia in our population sample.

Genomewide genetic linkage analysis confirms the presence of susceptibility loci for schizophrenia, on chromosomes 1q32.2, 5q33.2, and 8p21-22 and provides support for linkage to schizophrenia, on chromosomes 11q23.3-24 and 20q12.1-11.23

We have performed genetic linkage analysis in 13 large multiply affected families, to test the hypothesis that there is extensive heterogeneity of linkage for genetic subtypes of schizophrenia. Our strategy consisted of selecting 13 kindreds containing multiple affected cases in three or more generations, an absence of bipolar affective disorder, and a single progenitor source of schizophrenia with unilineal transmission into the branch of the kindred sampled. DNA samples from these families were genotyped with 365 microsatellite markers spaced at approximately 10-cM intervals across the whole genome. We observed LOD scores >3.0 at five distinct loci, either in the sample as a whole or within single families, strongly suggesting etiological heterogeneity. Heterogeneity LOD scores >3.0 in the sample as a whole were found at 1q33.2 (LOD score 3.2; P=.0003), 5q33.2 (LOD score 3.6; P=.0001), 8p22.1-22 (LOD score 3.6; P=.0001), and 11q21 (LOD score 3.1; P=.0004). LOD scores >3.0 within single pedigrees were found at 4q13-31 (LOD score 3.2; P=.0003) and at 11q23.3-24 (LOD score 3.2; P=.0003). A LOD score of 2.9 was also found at 20q12.1-11.23 within in a single family. The fact that other studies have also detected LOD scores >3.0 at 1q33.2, 5q33.2, 8p21-22 and 11q21 suggests that these regions do indeed harbor schizophrenia-susceptibility loci. We believe that the weight of evidence for linkage to the chromosome 1q22, 5q33.2, and 8p21-22 loci is now sufficient to justify intensive investigation of these regions by methods based on linkage disequilibrium. Such studies will soon allow the identification of mutations having a direct effect on susceptibility to schizophrenia.