Genetic sensitivity to stress modifies the relationship between socioeconomic status and major adverse cardiovascular events

Background

Lower socioeconomic status (SES) associates with major adverse cardiovascular events (MACE), in part through stress-related neural pathways that elicit inflammation. However, it is unknown whether genes that heighten stress sensitivity modify the association between lower SES and MACE.

Purpose

To assess whether genetic predisposition to stress sensitivity would modify the link between low SES and MACE

Methods

13,154 participants (median age 60 yrs, 41% male) from the Mass General Brigham Biobank were studied. A polygenic risk score for neuroticism (nPRS) was used as a measure of genetic predisposition to stress sensitivity (GSS). Using home addresses, SES was evaluated as median income and area deprivation index (ADI). Stress-related neural activity (SNA) was assessed (N=978) using validated FDG PET/CT imaging methods. MACE, and cardiovascular disease (CVD) risk factors were evaluated. Mediation analyses were employed.

Results

Over median (IQR) 4.9 (4.1–5.9) years of follow-up, 1,030 (7.8%) individuals had MACE. Lower SES (as low income, or alternatively as high ADI) associated with incident MACE among individuals with higher GSS (nPRS ≥ median) but not lower GSS (Fig. 1A and 1B). Similarly, lower SES associated with SNA among individuals with higher but not lower GSS (Fig. 1C). SNA mediated the relationship between income and MACE (P<0.05**) among those with higher GSS.

Conclusions

Genetic predisposition to stress sensitivity appears to heighten CVD risk associated with lower SES. This relationship may result from differential activation of stress-related neural pathways.

Funding Acknowledgement

Type of funding sources: None.

Largest GWAS of PTSD (N=20 070) yields genetic overlap with schizophrenia and sex differences in heritability

The Psychiatric Genomics Consortium-Posttraumatic Stress Disorder group (PGC-PTSD) combined genome-wide case-control molecular genetic data across 11 multiethnic studies to quantify PTSD heritability, to examine potential shared genetic risk with schizophrenia, bipolar disorder, and major depressive disorder and to identify risk loci for PTSD. Examining 20 730 individuals, we report a molecular genetics-based heritability estimate (h2SNP) for European-American females of 29% that is similar to h2SNP for schizophrenia and is substantially higher than h2SNP in European-American males (estimate not distinguishable from zero). We found strong evidence of overlapping genetic risk between PTSD and schizophrenia along with more modest evidence of overlap with bipolar and major depressive disorder. No single-nucleotide polymorphisms (SNPs) exceeded genome-wide significance in the transethnic (overall) meta-analysis and we do not replicate previously reported associations. Still, SNP-level summary statistics made available here afford the best-available molecular genetic index of PTSD-for both European- and African-American individuals-and can be used in polygenic risk prediction and genetic correlation studies of diverse phenotypes. Publication of summary statistics for ∼10 000 African Americans contributes to the broader goal of increased ancestral diversity in genomic data resources. In sum, the results demonstrate genetic influences on the development of PTSD, identify shared genetic risk between PTSD and other psychiatric disorders and highlight the importance of multiethnic/racial samples. As has been the case with schizophrenia and other complex genetic disorders, larger sample sizes are needed to identify specific risk loci.

Characterizing sleep spindles in 11,630 individuals from the National Sleep Research Resource

Sleep spindles are characteristic electroencephalogram (EEG) signatures of stage 2 non-rapid eye movement sleep. Implicated in sleep regulation and cognitive functioning, spindles may represent heritable biomarkers of neuropsychiatric disease. Here we characterize spindles in 11,630 individuals aged 4 to 97 years, as a prelude to future genetic studies. Spindle properties are highly reliable but exhibit distinct developmental trajectories. Across the night, we observe complex patterns of age- and frequency-dependent dynamics, including signatures of circadian modulation. We identify previously unappreciated correlates of spindle activity, including confounding by body mass index mediated by cardiac interference in the EEG. After taking account of these confounds, genetic factors significantly contribute to spindle and spectral sleep traits. Finally, we consider topographical differences and critical measurement issues. Taken together, our findings will lead to an increased understanding of the genetic architecture of sleep spindles and their relation to behavioural and health outcomes, including neuropsychiatric disorders.

Sleep patterns vary and are associated with health and disease. Here Purcell et al characterize sleep spindle activity in 11,630 individuals and describe age-related changes, genetic influences, and possible confounding effects, serving as a resource for further understanding the physiology of sleep.

COMT Val(158) Met genotype is associated with reward learning: a replication study and meta-analysis

Identifying mechanisms through which individual differences in reward learning emerge offers an opportunity to understand both a fundamental form of adaptive responding as well as etiological pathways through which aberrant reward learning may contribute to maladaptive behaviors and psychopathology. One candidate mechanism through which individual differences in reward learning may emerge is variability in dopaminergic reinforcement signaling. A common functional polymorphism within the catechol-O-methyl transferase gene (COMT; rs4680, Val(158) Met) has been linked to reward learning, where homozygosity for the Met allele (linked to heightened prefrontal dopamine function and decreased dopamine synthesis in the midbrain) has been associated with relatively increased reward learning. Here, we used a probabilistic reward learning task to asses response bias, a behavioral form of reward learning, across three separate samples that were combined for analyses (age: 21.80 ± 3.95; n = 392; 268 female; European-American: n = 208). We replicate prior reports that COMT rs4680 Met allele homozygosity is associated with increased reward learning in European-American participants (β = 0.20, t = 2.75, P < 0.01; ΔR(2) = 0.04). Moreover, a meta-analysis of 4 studies, including the current one, confirmed the association between COMT rs4680 genotype and reward learning (95% CI -0.11 to -0.03; z = 3.2; P < 0.01). These results suggest that variability in dopamine signaling associated with COMT rs4680 influences individual differences in reward which may potentially contribute to psychopathology characterized by reward dysfunction.

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.

Genome-wide association study identifies SESTD1 as a novel risk gene for lithium-responsive bipolar disorder

This corrects the article DOI: 10.1038/mp.2015.165.

A genome-wide association study of kynurenic acid in cerebrospinal fluid: implications for psychosis and cognitive impairment in bipolar disorder

Elevated cerebrospinal fluid (CSF) levels of the glia-derived N-methyl-D-aspartic acid receptor antagonist kynurenic acid (KYNA) have consistently been implicated in schizophrenia and bipolar disorder. Here, we conducted a genome-wide association study based on CSF KYNA in bipolar disorder and found support for an association with a common variant within 1p21.3. After replication in an independent cohort, we linked this genetic variant-associated with reduced SNX7 expression-to positive psychotic symptoms and executive function deficits in bipolar disorder. A series of post-mortem brain tissue and in vitro experiments suggested SNX7 downregulation to result in a caspase-8-driven activation of interleukin-1β and a subsequent induction of the brain kynurenine pathway. The current study demonstrates the potential of using biomarkers in genetic studies of psychiatric disorders, and may help to identify novel drug targets in bipolar disorder.

The KMO allele encoding Arg452 is associated with psychotic features in bipolar disorder type 1, and with increased CSF KYNA level and reduced KMO expression

The kynurenine pathway metabolite kynurenic acid (KYNA), modulating glutamatergic and cholinergic neurotransmission, is increased in cerebrospinal fluid (CSF) of patients with schizophrenia or bipolar disorder type 1 with psychotic features. KYNA production is critically dependent on kynurenine 3-monooxygenase (KMO). KMO mRNA levels and activity in prefrontal cortex (PFC) are reduced in schizophrenia. We hypothesized that KMO expression in PFC would be reduced in bipolar disorder with psychotic features and that a functional genetic variant of KMO would associate with this disease, CSF KYNA level and KMO expression. KMO mRNA levels were reduced in PFC of bipolar disorder patients with lifetime psychotic features (P=0.005, n=19) or schizophrenia (P=0.02, n=36) compared with nonpsychotic patients and controls. KMO genetic association to psychotic features in bipolar disorder type 1 was studied in 493 patients and 1044 controls from Sweden. The KMO Arg(452) allele was associated with psychotic features during manic episodes (P=0.003). KMO Arg(452) was studied for association to CSF KYNA levels in an independent sample of 55 Swedish patients, and to KMO expression in 717 lymphoblastoid cell lines and 138 hippocampal biopsies. KMO Arg(452) associated with increased levels of CSF KYNA (P=0.03) and reduced lymphoblastoid and hippocampal KMO expression (P≤0.05). Thus, findings from five independent cohorts suggest that genetic variation in KMO influences the risk for psychotic features in mania of bipolar disorder patients. This provides a possible mechanism for the previous findings of elevated CSF KYNA levels in those bipolar patients with lifetime psychotic features and positive association between KYNA levels and number of manic episodes.

Psychosocial stressors and the prognosis of major depression: a test of Axis IV

BACKGROUND

Axis IV is for reporting 'psychosocial and environmental problems that may affect the diagnosis, treatment and prognosis of mental disorders'. No studies have examined the prognostic value of Axis IV in DSM-IV.

METHOD

We analyzed data from 2497 participants in the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) with major depressive episode (MDE). We hypothesized that psychosocial stressors predict a poor prognosis of MDE. Secondarily, we hypothesized that psychosocial stressors predict a poor prognosis of anxiety and substance use disorders. Stressors were defined according to DSM-IV's taxonomy, and empirically using latent class analysis (LCA).

RESULTS

Primary support group problems, occupational problems and childhood adversity increased the risks of depressive episodes and suicidal ideation by 20-30%. Associations of the empirically derived classes of stressors with depression were larger in magnitude. Economic stressors conferred a 1.5-fold increase in risk for a depressive episode [95% confidence interval (CI) 1.2-1.9]; financial and interpersonal instability conferred a 1.3-fold increased risk of recurrent depression (95% CI 1.1-1.6). These two classes of stressors also predicted the recurrence of anxiety and substance use disorders. Stressors were not related to suicidal ideation independent from depression severity.

CONCLUSIONS

Psychosocial and environmental problems are associated with the prognosis of MDE and other Axis I disorders. Although DSM-IV's taxonomy of stressors stands to be improved, these results provide empirical support for the prognostic value of Axis IV. Future work is needed to determine the reliability of Axis IV assessments in clinical practice, and the usefulness of this information to improving the clinical course of mental disorders.

Multi-locus genome-wide association analysis supports the role of glutamatergic synaptic transmission in the etiology of major depressive disorder

Major depressive disorder (MDD) is a common psychiatric illness characterized by low mood and loss of interest in pleasurable activities. Despite years of effort, recent genome-wide association studies (GWAS) have identified few susceptibility variants or genes that are robustly associated with MDD. Standard single-SNP (single nucleotide polymorphism)-based GWAS analysis typically has limited power to deal with the extensive heterogeneity and substantial polygenic contribution of individually weak genetic effects underlying the pathogenesis of MDD. Here, we report an alternative, gene-set-based association analysis of MDD in an effort to identify groups of biologically related genetic variants that are involved in the same molecular function or cellular processes and exhibit a significant level of aggregated association with MDD. In particular, we used a text-mining-based data analysis to prioritize candidate gene sets implicated in MDD and conducted a multi-locus association analysis to look for enriched signals of nominally associated MDD susceptibility loci within each of the gene sets. Our primary analysis is based on the meta-analysis of three large MDD GWAS data sets (total N=4346 cases and 4430 controls). After correction for multiple testing, we found that genes involved in glutamatergic synaptic neurotransmission were significantly associated with MDD (set-based association P=6.9 × 10(-4)). This result is consistent with previous studies that support a role of the glutamatergic system in synaptic plasticity and MDD and support the potential utility of targeting glutamatergic neurotransmission in the treatment of MDD.

Using electronic medical records to enable large-scale studies in psychiatry: treatment resistant depression as a model

BACKGROUND

Electronic medical records (EMR) provide a unique opportunity for efficient, large-scale clinical investigation in psychiatry. However, such studies will require development of tools to define treatment outcome.

METHOD

Natural language processing (NLP) was applied to classify notes from 127 504 patients with a billing diagnosis of major depressive disorder, drawn from out-patient psychiatry practices affiliated with multiple, large New England hospitals. Classifications were compared with results using billing data (ICD-9 codes) alone and to a clinical gold standard based on chart review by a panel of senior clinicians. These cross-sectional classifications were then used to define longitudinal treatment outcomes, which were compared with a clinician-rated gold standard.

RESULTS

Models incorporating NLP were superior to those relying on billing data alone for classifying current mood state (area under receiver operating characteristic curve of 0.85-0.88 v. 0.54-0.55). When these cross-sectional visits were integrated to define longitudinal outcomes and incorporate treatment data, 15% of the cohort remitted with a single antidepressant treatment, while 13% were identified as failing to remit despite at least two antidepressant trials. Non-remitting patients were more likely to be non-Caucasian (p<0.001).

CONCLUSIONS

The application of bioinformatics tools such as NLP should enable accurate and efficient determination of longitudinal outcomes, enabling existing EMR data to be applied to clinical research, including biomarker investigations. Continued development will be required to better address moderators of outcome such as adherence and co-morbidity.

Meta-analysis of genome-wide association studies identifies common variants in CTNNA2 associated with excitement-seeking

The tendency to seek stimulating activities and intense sensations define excitement-seeking, a personality trait akin to some aspects of sensation-seeking. This trait is a central feature of extraversion and is a component of the multifaceted impulsivity construct. Those who score high on measures of excitement-seeking are more likely to smoke, use other drugs, gamble, drive recklessly, have unsafe/unprotected sex and engage in other risky behaviors of clinical and social relevance. To identify common genetic variants associated with the Excitement-Seeking scale of the Revised NEO Personality Inventory, we performed genome-wide association studies in six samples of European ancestry (N=7860), and combined the results in a meta-analysis. We identified a genome-wide significant association between the Excitement-Seeking scale and rs7600563 (P=2 × 10(-8)). This single-nucleotide polymorphism maps within the catenin cadherin-associated protein, alpha 2 (CTNNA2) gene, which encodes for a brain-expressed α-catenin critical for synaptic contact. The effect of rs7600563 was in the same direction in all six samples, but did not replicate in additional samples (N=5105). The results provide insight into the genetics of excitement-seeking and risk-taking, and are relevant to hyperactivity, substance use, antisocial and bipolar disorders.

Using linkage information to weight a genome-wide association of bipolar disorder

Issues of multiple-testing and statistical significance in genomewide association studies (GWAS) have prompted statistical methods utilizing prior data to increase the power of association results. Using prior findings from genome-wide linkage studies on bipolar disorder (BPD), we employed a weighted false discovery approach (wFDR; [Roeder et al. 2006. Am J Hum Genet 78(2): 243–252]) to previously reported GWAS data drawn from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). Using this method, association signals are up or down-weighted given the linkage score in that genomic region. Although no SNPs in our sample reached genome-wide significance through the wFDR approach, the strongest single SNP result from the original GWAS results (rs4939921 in myosin VB) is strongly up-weighted as it occurs on a linkage peak of chromosome 18. We also identify regions on chromosome 9, 17, and 18 where modestly associated SNP clusters coincide with strong linkage scores, implicating them as possible candidate regions for further analysis. Moving forward, we believe the application of prior linkage information will be increasingly useful to future GWAS studies that incorporate rarer variants into their analysis.

Whole-genome association study of bipolar disorder

We performed a genome-wide association scan in 1461 patients with bipolar (BP) 1 disorder, 2008 controls drawn from the Systematic Treatment Enhancement Program for Bipolar Disorder and the University College London sample collections with successful genotyping for 372,193 single nucleotide polymorphisms (SNPs). Our strongest single SNP results are found in myosin5B (MYO5B; P=1.66 x 10(-7)) and tetraspanin-8 (TSPAN8; P=6.11 x 10(-7)). Haplotype analysis further supported single SNP results highlighting MYO5B, TSPAN8 and the epidermal growth factor receptor (MYO5B; P=2.04 x 10(-8), TSPAN8; P=7.57 x 10(-7) and EGFR; P=8.36 x 10(-8)). For replication, we genotyped 304 SNPs in family-based NIMH samples (n=409 trios) and University of Edinburgh case-control samples (n=365 cases, 351 controls) that did not provide independent replication after correction for multiple testing. A comparison of our strongest associations with the genome-wide scan of 1868 patients with BP disorder and 2938 controls who completed the scan as part of the Wellcome Trust Case-Control Consortium indicates concordant signals for SNPs within the voltage-dependent calcium channel, L-type, alpha 1C subunit (CACNA1C) gene. Given the heritability of BP disorder, the lack of agreement between studies emphasizes that susceptibility alleles are likely to be modest in effect size and require even larger samples for detection.

Further evidence of association between two NET single-nucleotide polymorphisms with ADHD

The norepinephrine transporter (NET) gene is an attractive candidate gene for attention-deficit hyperactivity disorder (ADHD). Noradrenergic systems are critical to higher brain functions such as attention and executive function, which are defective in ADHD. The clinical efficacy of medications that target NET also supports its role in the etiology of ADHD. Here, we have applied a dense mapping strategy to capture all genetic variations within the NET gene in a large number of ADHD families (474 trios). As a result, we found association of the same alleles from two single-nucleotide polymorphisms (rs3785143 and rs11568324) previously identified in another large-scale ADHD genetic study (International Multisite ADHD Geneproject). Furthermore, the effect sizes were consistent across both studies. This is the first time that identical alleles of NET from different studies were implicated, and thus our report provides further evidence that the NET gene is involved in the etiology of ADHD.

Investigation of variation in SNAP-25 and ADHD and relationship to co-morbid major depressive disorder

Synaptosomal-associated protein of 25 kDa (SNAP-25), a protein involved in presynaptic neurotransmitter release, is a candidate gene for attention deficit/hyperactivity disorder (ADHD). Previous investigators have reported association initially with two single nucleotide polymorphisms (SNPs) (rs3746544, rs1051312) and their associated haplotypes. Subsequently, additional SNPs across the region were also reported to be associated with ADHD. We attempted to replicate these observations in a sample of 229 families with ADHD offspring by genotyping 61 SNPs spanning the region containing SNAP-25. A single SNP (rs3787283) which is in strong linkage disequilibrium (LD) with rs3746544 and rs1051312 (D' = 0.89-0.94) resulted in a nominally significant association (P = 0.002). When we pooled our data with those from prior studies, results were modestly significant for rs3746544 (P = 0.048) and rs6077690 (P = 0.031). As an attempt to determine if specific ADHD-related phenotypes may be more relevant to SNAP-25 than the categorical diagnosis, we carried out exploratory subgroup analysis in our ADHD sample according to co-morbid status. We found the strongest association result in the ADHD patients with co-morbid major depressive disorder (MDD). Six SNPs were nominally associated with the ADHD and co-morbid MDD cases (P = 0.012-0.045). Furthermore, a haplotype block located 11 kb 3' of the gene showed positive evidence for association with this phenotype (global P = 0.013). In conclusion, we report some evidence supporting the association of previously implicated SNPs (rs3746544, rs1051312) of SNAP-25 to ADHD. We further suggest that co-morbidity with MDD may enhance detection of the association between SNAP-25 and ADHD.

Evidence for an Association of the Dopamine D5 Receptor Gene on Age at Onset of Attention Deficit Hyperactivity Disorder

The purpose of this study was to determine whether the single nucleotide polymorphisms (SNPs) within candidate genes for attention deficit hyperactivity disorder (ADHD) are associated with the age at onset for ADHD. One hundred and forty-three SNPs were genotyped across five candidate genes (DRD5, SLC6A3, HTR1B, SNAP25, DRD4) for ADHD in 229 families with at least one affected offspring. SNPs with the highest estimated power to detect an association with age at onset were selected for each candidate gene, using a power-based screening procedure that does not compromise the nominal significance level. A time-to-onset analysis for family-based samples was performed on these SNPs to determine if an association exists with age at onset for ADHD. Seven consecutive SNPs surrounding the D5 dopamine receptor gene (DRD5), were associated with the age at onset for ADHD; FDR adjusted q-values ranged from 0.008 to 0.023. This analysis indicates that individuals with the risk genotype develop ADHD earlier than individuals with any other genotype. A haplotype analysis across the 6 significant SNPs that were in linkage disequilibrium with one another, CTCATA, was also found to be significant (p-value = 0.02). We did not observe significant associations with age at onset for the other candidate loci tested. Although definitive conclusions await independent replication, these results suggest that a variant in DRD5 may affect age at onset for ADHD.

A study of how socioeconomic status moderates the relationship between SNPs encompassing BDNF and ADHD symptom counts in ADHD families

Recent animal research suggests that brain-derived neurotrophic factor (BDNF), may mediate response to different environmental stimuli. In this paper, we evaluated the possible role of BDNF as a moderator of attention deficit hyperactivity disorder (ADHD) in the context of different socioeconomic classes. We genotyped ten single nucleotide polymorphisms (SNPs) in and around BDNF in 229 families and evaluate whether there are SNP-by-socioeconomic status (SES) interactions for attention deficit hyperactivity. We developed three quantitative phenotypes for ADHD from nine inattentive and nine hyperactive-impulsive symptoms that were used in SNP-by-SES interaction analyses using a new methodology implemented in the computer program PBAT. Findings were adjusted for multiple comparisons using the false discovery rate. We found multiple significant SNP-by-SES interactions using the inattentive symptom count. This study suggests that different SES classes may modify the effect of the functional variant(s) in and around BDNF to have an impact on the number of ADHD symptom counts that are observed. The two exons within BDNF represent potential functional variants that may be causing the observed associations.

Childhood history of anxiety disorders among adults with social phobia: rates, correlates, and comparisons with patients with panic disorder

We examined the rates and correlates of a childhood history of anxiety disorders in 100 adults with a primary diagnosis of social phobia (social anxiety disorder). Adulthood and childhood disorders were assessed by experienced clinicians with structured clinical interviews. Rates of childhood anxiety disorders were evaluated to diagnostic comorbidity and a comparison group of patients with panic disorder. Onset of social phobia occurred before age 18 in 80% of the sample. Over half of the sample (54%) met criteria for one or more childhood anxiety disorders other than social phobia: 47% for overanxious disorder, 25% for avoidant disorder, 13% for separation anxiety disorder, and 1% for childhood agoraphobia. A history of childhood anxiety was associated with an early age of onset of social phobia, greater severity of fear and avoidance of social situations, greater fears of negative evaluation, and greater anxiety and depression morbidity. Rates of childhood social phobia, overanxious disorder, and avoidant disorder were significantly higher in patients with social phobia relative to our panic-disordered comparison group. We found approximately equal rates of a childhood history of separation anxiety disorder in patients with social phobia and panic disorder, providing further evidence against a unique relationship between separation anxiety disorder and panic disorder.

Genetic association analysis of behavioral inhibition using candidate loci from mouse models

Genes influence the development of anxiety disorders, but the specific loci involved are not known. Genetic association studies of anxiety disorders are complicated by the complexity of the phenotypes and the difficulty in identifying appropriate candidate loci. We have begun to examine the genetics of behavioral inhibition to the unfamiliar (BI), a heritable temperamental predisposition that is a developmental and familial risk factor for panic and phobic disorders. Specific loci associated with homologous phenotypes in mouse models provide compelling candidate genes for human BI. We conducted family-based association analyses of BI using four genes derived from genetic studies of mouse models with features of behavioral inhibition. The sample included families of 72 children classified as inhibited by structured behavioral assessments. We observed modest evidence of association (P = 0.05) between BI and the glutamic acid decarboxylase gene (65 kDA isoform), which encodes an enzyme involved in GABA synthesis. No significant evidence of association was observed for the genes encoding the adenosine A(1A) receptor, the adenosine A(2A) receptor, or preproenkephalin. This study illustrates the potential utility of using candidate genes derived from mouse models to dissect the genetic basis of BI, a possible intermediate phenotype for panic and phobic disorders.

On the validity of the TDT test in the presence of comorbidity and ascertainment bias

Comorbidity, the association of two disorders, occurs commonly with complex diseases. In this paper, we investigate the effects of both true (within-family) comorbidity and spurious comorbidity due to ascertainment bias on the validity of both the parental and sibling control transmission/disequilibrium test. Specifically, we consider settings in which a candidate gene is unlinked to the target phenotype but is in linkage disequilibrium with a comorbid phenotype. We derive conditions under which the presence of true and/or spurious comorbidity will result in an artificial correlation between the target phenotype and the candidate gene.

The genetics of panic disorder

Of the anxiety disorders, panic disorder (PD) has been the most extensively studied from a genetic standpoint. Results of family studies have consistently demonstrated that PD runs in families, and twin studies indicate that genes contribute to this familiality. However, phenotypic and genetic complexity has made finding the specific genes involved in PD a challenge. There is still uncertainty about how best to define the phenotype for genetic studies and whether it is the clinical phenotype of PD or more latent psychologic and biologic traits that are inherited. To date, molecular genetic studies have suggested some chromosomal regions and genes that may contribute to risk, but none of these have been established. We review the genetic epidemiology of PD as well as recent molecular genetic studies of the disorder, and conclude with a discussion of promising strategies that attempt to uncover specific genetic loci involved in the etiology of PD.

Targeted genome screen of panic disorder and anxiety disorder proneness using homology to murine QTL regions

Family and twin studies have indicated that genes influence susceptibility to panic and phobic anxiety disorders, but the location of the genes involved remains unknown. Animal models can simplify gene-mapping efforts by overcoming problems that complicate human pedigree studies including genetic heterogeneity and high phenocopy rates. Homology between rodent and human genomes can be exploited to map human genes underlying complex traits. We used regions identified by quantitative trait locus (QTL)-mapping of anxiety phenotypes in mice to guide a linkage analysis of a large multiplex pedigree (99 members, 75 genotyped) segregating panic disorder/agoraphobia. Two phenotypes were studied: panic disorder/agoraphobia and a phenotype ("D-type") designed to capture early-onset susceptibility to anxiety disorders. A total of 99 markers across 11 chromosomal regions were typed. Parametric lod score analysis provided suggestive evidence of linkage (lod = 2.38) to a locus on chromosome 10q under a dominant model with reduced penetrance for the anxiety-proneness (D-type) phenotype. Nonparametric (NPL) analysis provided evidence of linkage for panic disorder/agoraphobia to a locus on chromosome 12q13 (NPL = 4.96, P = 0.006). Modest evidence of linkage by NPL analysis was also found for the D-type phenotype to a region of chromosome 1q (peak NPL = 2.05, P = 0.035). While these linkage results are merely suggestive, this study illustrates the potential advantages of using mouse gene-mapping results and exploring alternative phenotype definitions in linkage studies of anxiety disorder.

Implications of comorbidity and ascertainment bias for identifying disease genes

Comorbidity, the co-occurrence of disorders, is frequently observed to occur at higher rates in clinically ascertained samples than in population-based samples. An explanation for this finding is that subjects suffering from multiple illnesses are more likely to seek medical care and receive a diagnostic evaluation. We refer to the component of the comorbidity between illnesses due to such ascertainment bias as "spurious comorbidity." When spurious comorbidity is present, an apparent association between a candidate locus and the phenotype of interest may actually be attributable to an association between the locus and a comorbid phenotype. This phenomenon, which we call "spurious comorbidity bias," could thus produce misleading association findings. In this article, we describe this phenomenon and demonstrate that it may produce marked bias in the conclusions of family-based association studies. Because of the extremely high rates of comorbidity among psychiatric disorders in clinical samples, this problem may be particularly salient for genetic studies of neuropsychiatric disorders. We conclude that ascertainment bias may contribute to the frequent difficulty in replicating candidate gene study findings in psychiatry. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:817-822, 2000.

Genetic polymorphism at the CLOCK gene locus and major depression

Genetic analysis in both mouse and Drosophila has indicated that the product of the CLOCK gene is an essential component of a circadian rhythm timing system. A single nucleotide polymorphism (SNP), T3111C, in the 3' flanking region of the human CLOCK gene has been identified. Homozygotes or heterozygotes for the 3111C allele have been reported to have higher mean scores on a measure of evening preference for activity (vs. morning preference) than subjects homozygous for the 3111T allele. Since major depression is hypothesized to be closely linked to circadian rhythms, we explored whether this polymorphism might be related to susceptibility to major depression. We also ascertained allele frequency in an African-American control population, to begin to evaluate population variation at this locus. CLOCK T3111C allele frequencies were determined in 280 European American (EA) subjects, 143 with a history of major depression and 137 screened controls, and in 58 African American (AA) screened control subjects, using a polymerase chain reaction (PCR) - restriction fragment length polymorphism (RFLP) method. There was no significant difference between EA depressed and control subjects in allele frequency. There was a significant difference in allele frequency between EA and AA subjects, demonstrating a potential for population stratification. In none of these groups were significant deviations from Hardy-Weinberg equilibrium found. The present data do not support an association between CLOCK gene alleles at the T3111C locus and major depression.

Anxiety disorders and tic severity in juveniles with Tourette's disorder

OBJECTIVE

It was hypothesized that comorbidity with anxiety disorders would predict tic severity in youths with Tourette's disorder (TD).

METHOD

Subjects were 190 youths meeting DSM-III-R diagnostic criteria for TD who were consecutively referred to a pediatric psychopharmacology program between 1994 and 1997. Subjects were initially evaluated with a clinical interview and the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Epidemiologic version. Statistical analysis used t tests, chi 2 tests, and logistic regression analysis.

RESULTS

One hundred thirty-four subjects were classified as mild/moderate and 56 as severe TD cases. No meaningful differences were found in socioeconomic status, gender distribution, or age at onset of TD between the 2 groups. The 2 groups could not be differentiated by the presence of comorbid mood or disruptive behavior disorders including attention-deficit hyperactivity disorder. Although obsessive-compulsive disorder (OCD) was overrepresented among the severe TD cases, the difference failed to reach statistical significance. Excluding social and simple phobias, all other anxiety disorders were more clearly overrepresented among subjects with severe TD; separation anxiety disorder most robustly predicted tic severity, irrespective of the presence of OCD or other anxiety disorders.

CONCLUSION

Findings suggest that non-OCD anxiety disorders in general and separation anxiety disorder in particular may be significantly associated with tic severity in referred TD patients.

Using recursive partitioning for exploration and follow-up of linkage and association analyses

We first conducted a genome-wide screen for association with discordant sibships using the multi allelic and diallelic SDT. Markers at D4S1628, D8S1109, D9S66 and D7S1797 showed multi-allelic association. Deleterious diallelic association was found for markers at D1S1613, D1S534, D3S2459, D7S1817, and D9S131. Protective association was found at markers D8S1109, D8S1136, and D9S66. We then incorporated these findings with previous linkage findings in the exploration of oligogenes and epistasis using recursive partitioning. We conclude that recursive partitioning can be a useful adjunct to traditional linkage and association analyses in the exploration of these effects.

Exploring linkage for alcoholism using affection status and quantitative event related potential phenotypes

Using genome-scan data from the Collaborative Study on the Genetics of Alcoholism (COGA), we compared results of linkage analyses using a qualitative alcoholism phenotype to results of linkage analyses using event related potential (ERP) quantitative phenotypes, and compared our results to the results of Reich et al. [1998] and Begleiter et al. [1998]. We describe a general and simple strategy for identifying regions of the genome which may harbor genes involved in alcohol dependence which takes into consideration the results of both the affection status and ERP linkage analyses.

Anxiety in patients with pulmonary disease: comorbidity and treatment

Anxiety is a common and sometimes disabling symptom among patients with respiratory disease. Anxiety disorders appear to be the most prevalent psychiatric disorders in clinical samples of patients with pulmonary disease. Recognition that the differential diagnosis of dyspnea and anxiety includes both pulmonary and psychiatric conditions can be crucial to appropriate medical management and minimizing iatrogenic harm. This article reviews the epidemiology, comorbidity, diagnosis, and treatment of anxiety syndromes in patients with pulmonary disease. Successful treatment of anxiety disorders can substantially improve quality of life and a variety of treatment options are available. Safe and effective pharmacotherapy requires attention to potential adverse drug effects on pulmonary function and drug-to-drug interactions. Nonpharmacological treatments such as cognitive/behavioral therapies offer effective treatment without the risk of medication side effects.

Panic and phobic anxiety: defining phenotypes for genetic studies

OBJECTIVE

With recent advances in molecular genetics, the rate-limiting step in identifying susceptibility genes for psychiatric disorders has become phenotype definition. The success of psychiatric genetics may require the development of a "genetic nosology" that can classify individuals in terms of the heritable aspects of psychopathology. The authors' aim is to begin to apply this analysis to the anxiety disorders, focusing on panic and phobic disorders.

METHOD

Two parallel traditions of defining anxiety phenotypes are reviewed: the first, more closely identified with clinical psychiatry, has identified categorical diagnoses (e.g., panic disorder and social phobia). The other, more closely identified with psychological studies of personality development, has examined dimensional traits (e.g., neuroticism) and anxious temperament (e.g., behavioral inhibition).

RESULTS

The authors suggest that a genetic nosology of panic and phobic disorders may incorporate features of both traditions and discuss strategies for optimizing genetic approaches to anxiety including 1) studying phenotypic extremes, 2) identifying biological trait markers, and 3) using animal models to identify candidate loci.

CONCLUSIONS

An important dividend from the effort to define the boundaries of heritable phenotypes for genetic studies of anxiety may be a refinement of the nosology of anxiety disorders.

How do clinicians respond to patients who miss appointments?

BACKGROUND

Although patients miss up to 60% of scheduled outpatient appointments, little is known about how clinicians respond to "no-shows." In an effort to determine how clinicians customarily handle missed appointments, we surveyed mental health clinicians and internists at 2 academic hospitals: a private psychiatric hospital and an urban general hospital.

METHOD

An anonymous questionnaire survey was mailed to psychiatrists, psychologists, and social workers at both hospitals and to internists at the general hospital. Clinicians were surveyed about their usual response to psychotherapy, psychopharmacology, and internal medicine patients who miss appointments.

RESULTS

Among the 356 responses (39.5%) to 902 mailed questionnaires, there was substantial variability in clinicians' reported handling of "no-show" patients, although psychiatrists tended to be initially less active in pursuing patients than were nonphysician therapists and internists. A number of clinical variables were associated with clinicians' responses including the perceived risk of a bad outcome, hospital site, support staff availability, and billing practices.

CONCLUSION

The results suggest that clinicians' responses to missed appointments are determined by a complex mixture of influences rather than adherence to a readily definable "standard of care."

Sertraline effects on dyspnea in patients with obstructive airways disease

Dyspnea can have a debilitating effect on psychosocial and physical functioning in patients with chronic obstructive airways disease. Previous research has suggested that treatment of concomitant mood or anxiety symptoms can improve dyspnea and exercise intolerance among patients with respiratory disease. The authors report here on a case series of 7 patients with obstructive airways disease who reported improvements in dyspnea after sertraline 25-100 mg/day was added to their medication regimens. Four of the seven patients did not appear to meet syndromal criteria for a mood or anxiety disorder. Subjective improvements in dyspnea may have been related to relief of mood or anxiety symptoms or to direct effects on central respiratory systems. Controlled studies are needed to clarify the potential antidyspneic effects of sertraline.

Panic, dyspnea, and asthma

Dyspnea, a cardinal symptom of asthma, is also a common feature of panic attacks. Patients with asthma have high rates of anxiety disorders, and respiratory illness may be a risk factor in the development of panic disorder. The diagnosis of anxiety disorders in patients with asthma can be challenging, but successful identification and treatment of anxiety can reduce morbidity and improve quality of life in these patients. Serotonergic anxiolytic medications and cognitive-behavioral therapy appear to be the treatments of choice for pathologic anxiety in patients with asthma.

Intermittent luteal phase sertraline treatment of dysphoric premenstrual syndrome

BACKGROUND

Dysphoric premenstrual syndrome (PMS) has been associated with serotonergic dysregulation, and serotonergic medications have been reported to alleviate the symptoms of PMS. We investigated the effects of the serotonin reuptake inhibitor sertraline given during only the luteal phase in women with dysphoric PMS.

METHOD

After baseline ratings were obtained during two menstrual cycles, 15 women with dysphoric PMS who also met DSM-IV criteria for premenstrual dysphoric disorder (PMDD) entered single-blind treatment with sertraline 100 mg/day for one full menstrual cycle. Women who responded to this treatment were randomly assigned to a four-cycle double-blind placebo-controlled crossover study in which sertraline 100 mg/day or placebo was each given only during luteal phases of two consecutive menstrual cycles.

RESULTS

Eleven (79%) of fourteen women responded to single-blind full-cycle treatment with sertraline and were randomly assigned to the double-blind crossover study. Three patients dropped out of the study while taking placebo owing to nonresponse. For the remaining patients, sertraline given during the luteal phase produced significant improvements in depression, impairment, and global ratings compared with placebo and was equivalent in efficacy to sertraline given during the entire menstrual cycle.

CONCLUSION

Women with dysphoric PMS who responded to continuous sertraline treatment responded equally well to sertraline treatment that was restricted to the luteal phase. Luteal phase treatment may have advantages in side effect burden and costs. Larger controlled trials are warranted to confirm this finding.

Panic anxiety, dyspnea, and respiratory disease. Theoretical and clinical considerations

There is intriguing evidence suggesting pathophysiologic relationships among dyspnea, hyperventilation, and panic anxiety. The symptoms of panic attacks and pulmonary disease overlap, so that panic anxiety can reflect underlying cardiopulmonary disease and dyspnea can reflect an underlying anxiety disorder. The pathogenesis of panic may be related to respiratory physiology by several mechanisms: the anxiogenic effects of hyperventilation, the catastrophic misinterpretation of respiratory symptoms, and/or a neurobiologic sensitivity to CO2, lactate, or other signals of suffocation. In a subset of patients with PD, incipient pulmonary dysfunction may also contribute to their anxiety symptoms. Patients with pulmonary disease, particularly those with obstructive lung disease, have a high rate of panic symptoms and PD. There is reason to believe that pulmonary disease constitutes a risk factor for the development of panic related to repeated experiences with dyspnea and life-threatening exacerbations of pulmonary dysfunction, repeated episodes of hypercapnia or hyperventilation, the use of anxiogenic medications, and the stress of coping with chronic disease. Panic in pulmonary patients may carry significant morbidity, including phobic avoidance of activity, overly aggressive treatment with anxiogenic medications, and more prolonged and frequent hospitalization. Successful treatment of panic in these patients can improve functional status and quality of life by relieving anxiety and dyspnea. Nonpharmacologic treatment of panic, including cognitive-behavioral approaches, can be useful in patients with concomitant respiratory disease. Sedating medications such as benzodiazepines should be used with caution in patients with pulmonary disease to avoid respiratory depression. Serotonergic antidepressants (SSRIs) and anxiolytics (buspirone) may be effective treatments for panic or generalized anxiety in pulmonary patients and have relatively little potential for significant adverse effects.

The longitudinal course and outcome of panic disorder

Converging lines of evidence from a variety of methods of inquiry support a developmental model for panic disorder that includes a constitutional predisposition for anxiety influenced by genetic, familial, cognitive-behavioral and psychosocial factors, early expression during childhood, and variable manifestations during the life-cycle. Studies of patients followed up after acute pharmacotherapy trials and those treated naturalistically are consistent with this model and portray panic disorder as a generally chronic condition with a longitudinal course marked by relatively brief intervals of remission and high rates of recurrence and relapse. Longitudinal and follow-up studies suggest that panic attack frequency responds more readily and rapidly to pharmacotherapy than do other aspects of panic disorder such as agoraphobia and generalized anxiety. In general, the presence of agoraphobia is associated with more severe symptoms, greater chronicity, and more limited response to treatment. Other variables associated with chronicity and treatment resistance include patient-related factors (psychiatric and medical comorbidity, anxiety sensitivity) and pharmacologic factors (adequacy of dose, duration, and compliance). Although it is currently difficult to predict the duration of treatment needed for an individual patient, available evidence suggests that a substantial proportion of patients may require chronic treatment for panic disorder.

Genetic map of rat chromosome 5 including the fatty (fa) locus

Thirteen loci, including the obesity gene fatty (fa), were incorporated into a linkage map of rat Chromosome (Chr) 5. These loci were mapped in obese (fa/fa) progeny of a cross between BN x 13M-fal+F1 animals. Obese rats were scored for BN and 13M alleles at four loci (Ifna, D1S85h, C8b, and Lck1) by restriction fragment length polymorphisms and at eight additional loci (Glut1, Sv4j2, R251, R735, R980, R252, R371, and R1138) by simple sequence length polymorphisms (SSLP). The resulting map spans 67.3 cM of Chr5, presenting nine previously unmapped loci and one locus (Lck1) previously assigned to Chr 5 by use of somatic cell hybrid lines. Seven of the eight SSLP loci are newly identified; the SSLP linkage group alone spans 56.8 cM. The order of the loci is Sv4j2-R251-R735-R980-R1138-Ifna-fa-+ ++D1S85h-C8b-(Glut1-R252-R371)-Lck1. One locus, D1S85h, was found to lie only 0.4 cM from fa, close enough to serve as a reliable marker for the prediction of phenotype from genotype, and will be useful also for studies on the development of obesity in the fatty rat.

The Zucker fatty (fa) gene is not a mutation of corticotropin-releasing factor

Corticotropin-releasing factor (CRF) appears to regulate several physiological systems that display prominent abnormalities in Zucker fatty (fa/fa) rats, including the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and feeding behavior. Moreover, central administration of CRF ameliorates the obese phenotype. In light of these observations, the gene for CRF is a plausible candidate for the defective gene in the Zucker fatty rat. We report here the use of molecular genetic linkage analysis to test the hypothesis that fa is a mutant allele of the CRF gene. A restriction fragment length polymorphism for CRF between Zucker (13M) and Brown Norway (BN) DNA allowed us to examine segregation of 13M and BN CRF alleles relative to fa in 58 obese (fa/fa) F2 progeny of a 13MBN fa/+F1 intercross. If fa = CRF, all animals homozygous for the fatty mutation should be homozygous for the 13M CRF allele. However, only 10/58 fa/fa animals were homozygous for the 13M CRF allele, indicating that fa and CRF are not allelic. Thus, although CRF may be important in the physiology of Zucker rat obesity, fa is not a CRF mutation. Using a mouse C57BL/6J Spretus F1 x C57BL DBA/2J F1 intercross, we were able to demonstrate that the mouse CRF gene is linked to the carbonic anhydrase II (Car-2) gene on mouse chromosome 3, in a region of synteny-homology with rat chromosome 2. Thus the rat CRF gene is probably located on chromosome 2.

A molecular genetic method for genotyping fatty (fa/fa) rats

After three decades of physiological research, the precise nature of the genetic lesion in Zucker fatty (fa/fa) rats remains unknown. Several methods have been used to identify preobese rats to detect the earliest phenotypic effects of the fa mutation. Most of these methods have used phenotypic characteristics that are not reliable until the second week of life, when increased adiposity is already evident. We have used a restriction fragment length polymorphism (RFLP) for a human genomic DNA probe (VC85) that is tightly linked to the fa locus on rat chromosome 5 to genotype the F2 progeny of a Zucker (13M) x Brown Norway (BN) fa/+ F1 intercross. Sixty-four rats, comprising five litters, were killed at 5-6 wk of age. DNA was isolated either from tail at age 4-7 days (36 rats) or from organs at the time of death (28 rats). Adiposity was scored using inguinal fat pad weight as a percentage of body weight. RFLP analysis was > 99% accurate in identifying obese (fa/fa) rats. This molecular genetic method can be used to genotype fatty rats from an appropriate genetic cross at any age, even prenatally. Moreover, this method can distinguish heterozygous from homozygous littermates, enabling an analysis of gene dosage effects.

Skin malignancies in the elderly. Diagnosable, treatable, and potentially curable

Cutaneous malignancies are the most common tumors seen in the elderly population. They are often easily diagnosed while still in an early and potentially curable state. Basal cell carcinoma is the most frequently seen malignant neoplasm, followed by squamous cell carcinoma and malignant melanoma. Correct diagnosis depends on complete physical examination of the skin by health-care personnel who have been trained to recognize these lesions and appropriate referral to dermatologists or other experts in skin cancer.

Dieting and depression: a critical review

Investigations of affective changes during weight reduction have produced sharply conflicting results. Studies conducted through the 1950s and 1960s indicated that weight reduction was accompanied by a high incidence of affective disturbance ranging from simple dysphoria to clinical depression and psychosis. More recently, studies of behavioral programs have suggested that weight reduction may actually improve mood. A critical and systematic review of the literature revealed that the conflicting evidence is best explained by differences in mood assessment. The method of mood assessment consistently predicted the affective changes observed in previous reports. Other variables previously thought to influence affective response to weight reduction, including duration of treatment and weight loss, did not independently predict outcome.

Psychological and social aspects of the surgical treatment of obesity

New surgical procedures have revolutionized the treatment of morbid obesity (more than 100% overweight), a condition associated with serious medical complications and for which conservative treatment has been largely ineffective. These procedures, which are surprisingly safe, produce large weight losses and marked improvement in hypertension, diabetes, and other disorders influenced by obesity. Striking changes also occur in vocational and psychosocial functioning, including marital and sexual relations, in eating behavior, in food preferences, and in body image. The emotional state of patients during weight loss following surgery is far superior to that during attempts at weight reduction by other methods. The surgical procedures appear to produce a major biological change, perhaps lowering a body weight set point.