Personality in relation to genetic liability for schizophrenia and bipolar disorder: differential associations with the COMT Val 108/158 Met polymorphism

Association Analysis Between Catechol-O-Methyltransferase Expression and Cognitive Function in Patients with Schizophrenia, Bipolar Disorder, or Major Depression

INTRODUCTION

Schizophrenia, bipolar disorder (BD), and major depressive disorder are three common mental disorders. Although their diagnosis and treatment differ, they partially overlap.

METHODS

To explore the similarities and characteristics of these three psychiatric diseases, an intelligence quotient (IQ) assessment was performed to evaluate cognitive deficits. Relative catechol-O-methyltransferase (COMT) expression in peripheral blood mononuclear cells was examined in all three groups compared with healthy controls (HCs).

RESULTS

The results indicated that patients with any of the three psychiatric diseases presented IQ deficits, and that the first-episode schizophrenia (FES) group had even lower cognitive function than the other two groups. The relative COMT expression decreased in the FES group and increased in the BD group compared with the HC group. The correlation analysis of COMT expression level and IQ scores showed a positive correlation between relative COMT expression and full-scale IQ in the HC group. However, this correlation disappeared in all three psychiatric diseases studied.

CONCLUSION

In conclusion, this cross-disease strategy provided important clues to explain lower IQ scores and dysregulated COMT expression among three common mental illnesses.

Neural anomalies during vigilance in schizophrenia: Diagnostic specificity and genetic associations

Impaired vigilance is a core cognitive deficit in schizophrenia and may serve as an endophenotype (i.e., mark genetic liability). We used a continuous performance task with perceptually degraded stimuli in schizophrenia patients (N = 48), bipolar disorder patients (N = 26), first-degree biological relatives of schizophrenia patients (N = 55) and bipolar disorder patients (N = 28), as well as healthy controls (N = 68) to clarify whether previously reported vigilance deficits and abnormal neural functions were indicative of genetic liability for schizophrenia as opposed to a generalized liability for severe psychopathology. We also examined variation in the Catechol-O-methyltransferase gene to evaluate whether brain responses were related to genetic variation associated with higher-order cognition. Relatives of schizophrenia patients had an increased rate of misidentification of nontarget stimuli as targets when they were perceptually similar, suggestive of difficulties with contour perception. Larger early visual responses (i.e., N1) were associated with better task performance in patients with schizophrenia consistent with enhanced N1 responses reflecting beneficial neural compensation. Additionally, reduced N2 augmentation to target stimuli was specific to schizophrenia. Both patients with schizophrenia and first-degree relatives displayed reduced late cognitive responses (P3b) that predicted worse performance. First-degree relatives of bipolar patients exhibited performance deficits, and displayed aberrant neural responses that were milder than individuals with liability for schizophrenia and dependent on sex. Variation in the Catechol-O-methyltransferase gene was differentially associated with P3b in schizophrenia and bipolar groups. Poor vigilance in schizophrenia is specifically predicted by a failure to enhance early visual responses, weak augmentation of mid-latency brain responses to targets, and limited engagement of late cognitive responses that may be tied to genetic variation associated with prefrontal dopaminergic availability. Experimental results illustrate specific neural functions that distinguish schizophrenia from bipolar disorder and provides evidence for a putative endophenotype that differentiates genetic liability for schizophrenia from severe mental illness more broadly.

Association between COMT gene Val108/158Met and antidepressive treatment response: A meta-analysis

Multiple antidepressive treatment methods are widely used in the clinic, but different patients showed considerable differences in response to the same treatment. The catechol-O-methyltransferase (COMT) rs4680 polymorphism is involved in the antidepressive treatment reaction; however, the results in different studies are inconsistent. Thus, we performed a meta-analysis to explore the association of the COMT rs4680 polymorphism with the treatment response in major depressive disorder (MDD) patients. An online search was performed through PubMed, EMBASE and the Cochrane library up to December 2018. The odds ratios (ORs), 95% confidence intervals (95% CI) and heterogeneity were calculated in four genetic models. Subgroup analysis and Galbraith plot were carried out to detect the potential source of heterogeneity. Sensitivity and publication bias analyses were performed to identify the reliability of the results. A total of 11 studies involving 2845 individuals were included in this meta-analysis. The results of the subgroup analysis indicated that patients who carried the G allele had remission or a better response to electroconvulsive therapy (ECT) in four genetic models. Excluding the studies that might lead to heterogeneity, overall ORs were recalculated, and no obvious association between rs4680 polymorphism and therapeutic reaction was detected in the allelic, recessive and additive models. In the dominant model, COMT rs4680 variants showed significant associations with antidepressive treatment, but the result was highly dependent on the individual study. In addition, the patients with the GG or AG + GG genotype in comparison to AA were associated with a better response to ECT treatment. However, due to the small number of studies using ECT treatment, we suggest that more research should be performed to verify this result.

Personality traits across the psychosis spectrum: A Hierarchical Taxonomy of Psychopathology conceptualization of clinical symptomatology

Psychotic disorders have varied clinical presentations, diagnostic stability is poor and other mental disorders often co-occur with the conditions. To improve the clinical and pathophysiological utility of classification systems for psychosis, it is necessary to consider how symptoms may reflect dimensions of psychopathology that extend beyond the boundaries of traditional diagnostic classifications. We examined personality deviation as a means for explaining symptom variation across individuals with serious mental illness. Participants (N = 312) with psychosis, first-degree biological relatives and healthy controls underwent comprehensive clinical evaluations that included symptom ratings and Diagnostic Statistical Manual consensus diagnoses. They completed the Personality Inventory for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (PID-5), which provides multidimensional assessment of personality disturbances and characterizes psychosis-relevant phenomena, and the Schizotypal Personality Questionnaire (SPQ), a widely accepted measure of schizotypal traits. PID-5 was comparable with SPQ in differentiating between participants with and without psychosis. Greater psychotic symptomatology and higher scores on the SPQ Cognitive-perceptual dimension were associated with higher scores on PID-5 Psychoticism. Facet-level traits showed diverse associations with existing clinical syndromes, suggesting they have utility for quantifying separable symptom dimensions that cut across existing disorders. Yet the patient groups were similar across four of the five PID-5 personality trait domains, indicating shared patterns of personality expression that challenge existing categorical delineations. © 2019 John Wiley & Sons, Ltd.

Personality dimensions in schizophrenia: A family study

Studies have demonstrated that personality traits differ in schizophrenia patients and family members compared to controls, suggesting familial risk. This study evaluated personality traits in a family study of schizophrenia, as well as the relationship between personality traits and symptoms and social functioning in schizophrenia patients. Thirty-two schizophrenia patients, 28 adult non-psychotic relatives, and 27 community controls completed the Dimensional Assessment of Personality Pathology-Basic Questionnaire (DAPP-BQ). Schizophrenia patients differed on many dimensions of the DAPP-BQ compared to controls and/or relatives: affective lability, anxiousness, callousness, conduct problems, cognitive dysregulation, identity problem, intimacy, insecure attachment, low affiliation, narcissism, oppositionality, restricted expression, self-harm, submissiveness, and suspiciousness. No differences were found between relatives and controls. Furthermore, in schizophrenia patients, associations were found between personality and particularly general symptoms, as well as social functioning. Personality traits can be conceptualized as an extended phenotype in schizophrenia patients.

Association between neurological soft signs, temperament and character in patients with schizophrenia and non-psychotic relatives

The heritability of schizophrenia and most personality traits has been well established, but the role of personality in susceptibility to schizophrenia remains uncertain. The aim of this study was to test for an association between personality traits and Neurological Soft Signs (NSS), a well-known biological marker of schizophrenia, in non-psychotic relatives of patients with schizophrenia. For this purpose, we evaluated the NSS scale and personality measured by the Temperament and Character inventory (TCI-R) in three groups of subjects: 29 patients with schizophrenia, 24 unaffected relatives and 37 controls. The results showed that patients with schizophrenia were more asocial (higher harm avoidance and lower reward dependence), more perseverative (higher persistence), and more schizotypal (lower self-directedness and cooperativeness, higher self-transcendence). The unaffected relatives showed higher harm avoidance, lower self-directedness and cooperativeness than the healthy controls. Higher NSS scores and sub-scores were found in patients and non-psychotic relatives compared with the controls. Among all the patients, total NSS scores were positively correlated with harm avoidance but negatively correlated with novelty seeking and persistence. Total NSS were also correlated with low scores on self-directedness and cooperativeness, which are indicators of personality disorder. Our results show that susceptibility to NSS and to schizophrenia are both related to individual differences in the temperament and character features in non-psychotic relatives of patients with schizophrenia. High harm avoidance, low persistence, low self-directedness and low cooperativeness contribute to both the risk of NSS and schizophrenia. These findings highlight the value of using both assessments to study high risk populations.

The population genetics of pharmacogenomics VIP variants in the Sherpa population

Polymorphic distributions of pharmacogenes among some ethnicities are under-represented in current pharmacogenetic research. Particularly, there is a paucity of pharmacogenetic information in the Sherpa population in Tibet. We used the Sequenom MassARRAY single nucleotide polymorphism (SNP) genotyping technology to detect 86 very important pharmacogene (VIP) variants in Sherpas and compared the genotypic frequencies of these variants with HapMap populations. Overall, 59 of the 60 previously reported variants in the HapMap populations were found in our study. We found minimal differences between populations of Sherpas and Chinese Han in Beijing (CHB), Chinese in Metropolitan Denver, Colorado (CHD), Japanese in Tokyo, Japan (JPT), and Mexicans in Los Angeles, California (MEX) after a strict Bonferroni correction. Only 8, 4, 5, 4 VIP genotypes, respectively, were different in these groups. Additionally, pairwise FST values and clustering analyses showed that the VIP variants in the Sherpa population exhibited a close genetic affinity with the CHB and JPT populations, but they were most similar to the CHD population. Our results contribute to a better understanding of the molecular basis underlying ethnic differences in drug response, which may potentially benefit the development of personalized medicine for the Sherpa population.

Prefrontal inefficiency is associated with polygenic risk for schizophrenia

Considering the diverse clinical presentation and likely polygenic etiology of schizophrenia, this investigation examined the effect of polygenic risk on a well-established intermediate phenotype for schizophrenia. We hypothesized that a measure of cumulative genetic risk based on additive effects of many genetic susceptibility loci for schizophrenia would predict prefrontal cortical inefficiency during working memory, a brain-based biomarker for the disorder. The present study combined imaging, genetic and behavioral data obtained by the Mind Clinical Imaging Consortium study of schizophrenia (n = 255). For each participant, we derived a polygenic risk score (PGRS), which was based on over 600 nominally significant single nucleotide polymorphisms, associated with schizophrenia in a separate discovery sample comprising 3322 schizophrenia patients and 3587 control participants. Increased polygenic risk for schizophrenia was associated with neural inefficiency in the left dorsolateral prefrontal cortex after covarying for the effects of acquisition site, diagnosis, and population stratification. We also provide additional supporting evidence for our original findings using scores based on results from the Psychiatric Genomics Consortium study. Gene ontology analysis of the PGRS highlighted genetic loci involved in brain development and several other processes possibly contributing to disease etiology. Our study permits new insights into the additive effect of hundreds of genetic susceptibility loci on a brain-based intermediate phenotype for schizophrenia. The combined impact of many common genetic variants of small effect are likely to better reveal etiologic mechanisms of the disorder than the study of single common genetic variants.

Temperament and character in remitted and symptomatic patients with schizophrenia: modulation by the COMT Val158Met genotype

While research on remission in schizophrenia has gained attention, personality characteristics associated with remission in schizophrenia have been under-studied. A functional valine-to-methionine (Val158Met) polymorphism in the catechol-O-methyltransferase (COMT) gene is shown to modify clinical presentation of schizophrenia despite weak or no association with the disorder itself. Studies also report that this polymorphism can affect personality traits. We aimed to examine personality traits of remitted patients with schizophrenia as compared to symptomatic patients and healthy controls and to investigate whether the COMT Val158Met polymorphism influences their personality. Scores on the Temperament and Character Inventory were compared between 34 remitted outpatients with schizophrenia, age- and sex-matched 72 symptomatic outpatients with schizophrenia, and matched 247 healthy individuals. The effect of COMT Val158Met polymorphism on personality was examined in each group. The analysis of covariance, controlling for confounding variables, revealed that compared to healthy controls, symptomatic patients exhibited a pervasively altered personality profile whereas remitted patients showed alterations in more limited personality dimensions and demonstrated normal levels of novelty-seeking, reward dependence and cooperativeness. The two-way analysis of covariance, with genotype and sex as between-subject factors and confounders as covariates, revealed that Met carriers demonstrated significantly lower reward dependence and cooperativeness than Val homozygotes in symptomatic patients; while no significant genotype effect was found in remitted patients or in healthy individuals. These findings indicate that remitted patients with schizophrenia have a relatively adaptive personality profile compared to symptomatic patients. The COMT Val158Met polymorphism might have a modulating effect on the relationship between personality and remission.

Schizoid personality disorder

Schizoid personality disorder (ScPD) is one of the "odd cluster" or "cluster A" personality disorders in DSM-IV. In the present article, the authors review information pertaining to the psychometric characteristics of ScPD as gleaned from a search of relevant publications as well as from databases of personality disorder study groups. Comparatively little evidence exists for the validity and reliability of ScPD as a separate, multifaceted personality disorder. Some authors, moreover, have contended that the group of patients termed "schizoid" actually fall into two distinct groups--an "affect constricted" group, who might better be subsumed within schizotypal personality disorder, and a "seclusive" group, who might better be subsumed within avoidant personality disorder. The research-based justification for retaining ScPD as an independent diagnosis is sufficiently sparse for it to seem reasonable to remove ScPD from the list of personality disorders in DSM-V, and instead to invite clinicians to code for schizoid traits using a dimensional model.

A COMT gene haplotype associated with methamphetamine abuse

INTRODUCTION

Methamphetamine (MAMP) use is highly associated with psychiatric disorders with 12-13% of MAMP-dependent patients experiencing psychotic symptoms. Substance abuse and dependence may primarily involve the mesolimbic pathway and dopaminergic brain structures. It follows that dopaminergic genes, particularly COMT (encoding catechol-O-methyltransferase) and its val158met polymorphism (rs4680), are natural candidates for susceptibility loci to addiction. We have previously found an association with rs4680 and MAMP addiction.

METHODS

We present additional genotyping of rs165599 in 423 cases and 502 controls of a Taiwanese MAMP user sample. We carried out an in-silico evaluation of rs165599 for a possible impact on microRNA binding or UTR stability. We also carried out a review of transcript sequences across the COMT 3'UTR.

RESULTS

Genotype counts were (cases/controls): AA 94/110, AG 198/210 and GG 93/109. There were no significant allele or genotype differences between cases and controls for rs165599. However, a haplotype main effect was detected using both rs4680 and rs165599 using the χ²-test in UNPHASED. The global P-value was P=0.0044 with the effect appearing to derive from one haplotype that is underrepresented in cases: A/G for rs4680/rs165599 (haplotype P=0.001). rs165599 is a single nucleotide polymorphism located in the COMT 3' untranslated region (UTR), a noncoding transcript region subject to posttranscriptional down-regulation by mechanisms such as microRNA binding. A review of transcript sequences across the COMT 3'UTR found evidence to suggest antisense interference of COMT from the 3'UTR of the neighbouring 'Armadillo repeat gene deleted in velocardiofacial syndrome' gene.

Genetic structure of personality factors and bipolar disorder in families segregating bipolar disorder

BACKGROUND

Bipolar disorder (BPD) has been associated with variations in personality dimensions, but the nature of this relationship has been unclear. In this study, the heritabilities of BPD and the Big Five personality factors and the genetic correlations between BPD and personality factors are reported.

METHODS

The participants in this study were 1073 individuals from 172 families of Mexican or Central American ancestry. Heritabilities and genetic correlations were calculated under a polygenic model using the maximum-likelihood method of obtaining variance components implemented in the SOLAR software package.

RESULTS

Heritabilities of 0.49, 0.43, and 0.43 were found for the narrowest phenotype (schizoaffective bipolar and bipolar I), the intermediate phenotype (schizoaffective bipolar, bipolar I, and bipolar II), and the broadest phenotype (schizoaffective bipolar, bipolar I, bipolar II, and recurrent depression), respectively. For the Big Five personality factors, heritabilities were 0.25 for agreeableness, 0.24 for conscientiousness, 0.24 for extraversion, 0.23 for neuroticism, and 0.32 for openness to experience. For the narrowest phenotype, a significant negative correlation (-0.32) with extraversion was found. For the broadest phenotype, negative correlations were found for agreeableness (-0.35), conscientiousness (-0.39), and extraversion (-0.44). A positive correlation (0.37) was found with neuroticism.

LIMITATIONS

It is not possible to determine whether aspects of personality are factors in the development of bipolar disorder or vice versa. The short form of the NEO does not provide the ability to examine in detail which facets of extraversion are most closely related to bipolar disorder or to compare our results with studies that have used the long version of the scale.

CONCLUSIONS

This study establishes a partial genetic basis for the Big Five personality factors in this set of families, while the environmental variances demonstrate that non-genetic factors are also important in their influence on bipolar and personality phenotypes. BPD may be most associated with decreased extraversion (less interaction with one's surroundings) because patients spend more time in depressive than manic states.

Personality disorder types proposed for DSM-5

The Personality and Personality Disorders Work Group has proposed five specific personality disorder (PD) types for DSM-5, to be rated on a dimension of fit: antisocial/psychopathic, avoidant, borderline, obsessive-compulsive, and schizotypal. Each type is identified by core impairments in personality functioning, pathological personality traits, and common symptomatic behaviors. The other DSM-IV-TR PDs and the large residual category of personality disorder not otherwise specified (PDNOS) will be represented solely by the core impairments combined with specification by individuals' unique sets of personality traits. This proposal has three main features: (1) a reduction in the number of specified types from 10 to 5; (2) description of the types in a narrative format that combines typical deficits in self and interpersonal functioning and particular configurations of traits and behaviors; and (3) a dimensional rating of the degree to which a patient matches each type. An explanation of these modifications in approach to diagnosing PD types and their justifications--including excessive co-morbidity among DSM-IV-TR PDs, limited validity for some existing types, lack of specificity in the definition of PD, instability of current PD criteria sets, and arbitrary diagnostic thresholds--are the subjects of this review.

Clinical endophenotypes for bipolar disorder

Although twin, family, and adoption studies demonstrate that bipolar disorder (BPD) is substantially heritable, the molecular genetic basis for this illness remains elusive. Given evidence that genes predisposing to BPD may be transmitted without expression of the clinical phenotype, interest has arisen in developing endophenotypes - indicators of processes mediating between genotype and phenotype. Patients with BPD have subtle neuropsychological abnormalities, even during periods of symptom remission. Some of these neurocognitive deficits are present in unaffected family members of probands with BPD, suggesting that these measures may be quantitative endophenotypes for the disorder. Similarly, BPD is associated with specific personality traits (e.g., reduced inhibition, increased risk-taking) that have been observed in both affected individuals and their family members. In this chapter, we review the evidence for candidate neurocognitive and personality endophenotypes for BPD. We conclude that neurocognitive and personality traits appear to be appropriate endophenotypes for BPD, suggesting that these measures share some genetic factors with the illness.

Association between catechol-O-methyltransferase Val(108/158)Met polymorphism and psychotic features of bipolar disorder

BACKGROUND

Catechol-O-methyltransferase (COMT) inactivates catecholamines, and a G-A transition in the COMT gene (rs4680) influences the enzyme activity and the interaction between cortical and subcortical dopaminergic neurotransmission. Studies in healthy participants and in patients affected by schizophrenia suggested that rs4680 can influence the propensity to develop psychotic symptoms, with the Met low-activity allele exerting a protective role. Previous studies in bipolar patients reported non-significant trends in the same direction.

METHODS

We genotyped rs4680 in a sample of 467 patients affected by bipolar disorder type I with or without a previous illness episode with psychotic features (DSM-IV criteria: delusions or hallucinations).

RESULTS

We observed a significant association between homozygosis for the rs4680 COMT low-activity variant and a reduced risk of experiencing illness episodes with psychotic features during the course of the illness. The Met/Met genotype was more common among patients without psychotic features, and while in the non-psychotic group the Val/Val genotype had a distribution similar to Met/Met, in the group of patients who experienced episodes with psychotic symptoms the proportion of Val/Val homozygotes was the double of Met/Met.

CONCLUSIONS

We suggest that rs4680 could be an inheritable aspect of the mechanisms of dopamine regulation that could influence the individual susceptibility of patients with bipolar disorder to develop psychotic symptoms.