Comorbidity between bipolar disorder and alcohol use disorder: association of dopamine and serotonin gene polymorphisms

The pharmacotherapeutic management of comorbid bipolar disorder and alcohol use disorder

INTRODUCTION

Comorbidity of bipolar disorder (BD) and alcohol use disorder (AUD) is very frequent resulting in detrimental outcomes, including increased mortality. Diagnosis of AUD in BD and vice versa is often delayed as symptoms of one disorder mimic and obscure the other one. Evidence for pharmacotherapies for people with comorbid BD and AUD remains limited, and further proof-of-concept studies are urgently needed.

AREAS COVERED

This paper explores the currently available pharmacotherapies for AUD, BD and their usefulness for comorbid BD and AUD. It also covers to some degree the epidemiology, diagnosis, and potential common neurobiological traits of comorbid BD and AUD.

EXPERT OPINION

The authors conclude that more controlled studies are needed before evidence-based guidance can be drawn up for clinician's use. Since there are no relevant pharmacological interactions, approved medications for AUD can also be used safely in BD. For mood stabilization, lithium should be considered first in adherent persons with BD and comorbid AUD. Alternatives include valproate, lamotrigine, and some atypical antipsychotics, with partial D2/D3 receptor agonism possibly being beneficial in AUD, too.

Incidence of and risk factors for alcohol dependence in bipolar disorder: A population-based cohort and nested case-control study

OBJECTIVES

Although alcohol dependence is highly prevalent in patients with bipolar disorder, the causal relationship is not yet well-established. This study estimated the incidence of alcohol dependence in a nationwide bipolar disorder cohort and examined risk factors for alcohol dependence.

METHODS

Patients aged 15-65 years with consistent bipolar disorder who had their first psychiatric admission between 1999 and 2012 (n = 21,791) were enrolled from the National Health Insurance Research Database in Taiwan. We calculated the adjusted incidence rate ratio of alcohol dependence in the bipolar cohort relative to the general population after stratification by age and sex. In the nested case-control study, we included patients with incident alcohol dependence as cases and four age- and sex-matched controls for each case to analyze health care utilization, comorbidities and concomitant medications between them.

RESULTS

We identified 1261 patients with bipolar disorder with incident alcohol dependence. Relative to the general population, the adjusted incidence rate ratio of alcohol dependence was 9.20 in the bipolar cohort. All adjusted incidence rate ratios were high across all age subgroups. Cases had higher psychiatric and nonpsychiatric health care utilization than did controls. Multivariate analysis revealed that cases tended to have cardiovascular disease, diabetes mellitus, chronic hepatic disease, pneumonia and delirium before alcohol dependence diagnosis. Cases had higher psychiatric comorbidities, namely drug-induced mental disorders, anxiety disorder, personality disorder, adjustment disorder and sleep disorder.

CONCLUSION

The bipolar cohort had a higher incidence of alcohol dependence. We identified specific groups with a high risk of alcohol dependence. Additional strategies for early detection, treatment and intervention for alcohol dependence should be developed.

Genetic Factors Associated With Tardive Dyskinesia: From Pre-clinical Models to Clinical Studies

Tardive dyskinesia is a severe motor adverse event of antipsychotic medication, characterized by involuntary athetoid movements of the trunk, limbs, and/or orofacial areas. It affects two to ten patients under long-term administration of antipsychotics that do not subside for years even after the drug is stopped. Dopamine, serotonin, cannabinoid receptors, oxidative stress, plasticity factors, signaling cascades, as well as CYP isoenzymes and transporters have been associated with tardive dyskinesia (TD) occurrence in terms of genetic variability and metabolic capacity. Besides the factors related to the drug and the dose and patients’ clinical characteristics, a very crucial variable of TD development is individual susceptibility and genetic predisposition. This review summarizes the studies in experimental animal models and clinical studies focusing on the impact of genetic variations on TD occurrence. We identified eight genes emerging from preclinical findings that also reached statistical significance in at least one clinical study. The results of clinical studies are often conflicting and non-conclusive enough to support implementation in clinical practice.

SERINC2 increases the risk of bipolar disorder in the Chinese population

BACKGROUND

Although common variants in a large collection of patients are associated with increased risk for bipolar disorder (BD), studies have only been able to predict 25%-45% of risks, suggesting that lots of variants that contribute to the risk for BD haven't been identified. Our study aims to identify novel BD risk genes.

METHODS

We performed whole-exome sequencing of 27 individuals from 6 BD multi-affected Chinese families to identify candidate variants. Targeted sequencing of one of the novel risk genes, SERINC2, in additional sporadic 717 BD patients and 312 healthy controls (HC) validated the association. Magnetic resonance imaging (MRI) were performed to evaluate the effect of the variant to brain structures from 213 subjects (4 BD subjects from a multi-affected family, 130 sporadic BD subjects and 79 HC control).

RESULTS

BD pedigrees had an increased burden of uncommon variants in extracellular matrix (ECM) and calcium ion binding. By large-scale sequencing we identified a novel recessive BD risk gene, SERINC2, which plays a role in synthesis of sphingolipid and phosphatidylserine (PS). MRI image results show the homozygous nonsense variant in SERINC2 affects the volume of white matter in cerebellum.

CONCLUSIONS

Our study identified SERINC2 as a risk gene of BD in the Chinese population.

Comorbid Bipolar and Alcohol Use Disorder-A Therapeutic Challenge

Comorbidity rates in Bipolar disorder rank highest among major mental disorders, especially comorbid substance use. Besides cannabis, alcohol is the most frequent substance of abuse as it is societally accepted and can be purchased and consumed legally. Estimates for lifetime comorbidity of bipolar disorder and alcohol use disorder are substantial and in the range of 40-70%, both for Bipolar I and II disorder, and with male preponderance. Alcohol use disorder and bipolarity significantly influence each other's severity and prognosis with a more complicated course of both disorders. Modern treatment concepts acknowledge the interplay between these disorders using an integrated therapy approach where both disorders are tackled in the same setting by a multi-professional team. Motivational interviewing, cognitive behavioral and socio- therapies incorporating the family and social environment are cornerstones in psychotherapy whereas the accompanying pharmacological treatment aims to reduce craving and to optimize mood stability. Adding valproate to lithium may reduce alcohol consumption whereas studies with antipsychotics or naltrexone and acamprosate did not affect mood fluctuations or drinking patterns. In summary, there is a continuous need for more research in order to develop evidence-based approaches for integrated treatment of this frequent comorbidity.

Smoking Genes: A Case-Control Study of Dopamine Transporter Gene (SLC6A3) and Dopamine Receptor Genes (DRD1, DRD2 and DRD3) Polymorphisms and Smoking Behaviour in a Malay Male Cohort

Dopamine receptor and dopamine transporter genes polymorphisms have been associated with cigarette smoking behaviour in different populations. The aim of this case-control study was to evaluate polymorphisms in the dopamine transporter gene (SLC6A3 (rs27072)) and the dopamine receptor genes (DRD1 (rs686), DRD2 (rs1800497) and DRD3 (rs7653787)) and their contribution to smoking behaviour in a Malay male population. We identified 476 participants over the age of 18 years comprising 238 smokers and 238 non-smokers. Information such as age, height, weight, body mass index, systolic and diastolic blood pressures, marital status, and smoking status of close family members were taken. For the genetic study, we genotyped four genes (SLC6A3 (rs27072), DRD1 (rs686), DRD2 (rs1800497) and DRD3 (rs7653787)) using the polymerase chain reaction-restriction fragment length polymorphism method and further confirmed our findings with sequencing. Dopamine receptor genes (DRD1, DRD2 and DRD3) were found to be associated with smoking behaviour in a Malay male population. The dopamine transporter gene (SLC6A3) did not show this association. Significant differences were observed between smokers' and non-smokers' age, systolic blood pressure, marital status and family members who smoke. Smoking behaviour is significantly influenced by genetic variations of DRD1, DRD2 and DRD3 in a Malay male population.

Genetic polymorphisms in neuroendocrine disorder-related candidate genes associated with pre-pregnancy obesity in gestational diabetes mellitus patients by using a stratification approach

Background

Certain candidate genes have been associated with obesity. The goal of this study is to determine the association between thirteen neuroendocrine disorder-related candidate genes and pre-pregnancy obesity among gestational diabetes mellitus (GDM) patients using the stratification approach defined the Asian and International criteria-based body mass index (BMI).

Methods

This was a post-hoc case-control exploratory sub-analysis of a cross-sectional study among GDM women to determine which candidate single nucleotide polymorphisms (SNPs) related to neuroendocrine disorders may be associated with obesity. Factors were adjusted for socio-demographic characteristics and concurrent medical problems in this particular population. Pre-pregnancy BMI and concurrent medical profiles were obtained from maternal health records. Obesity is defined as BMI of ≥27.5 kg/m² for Asian criteria-based BMI and >30 kg/m² for International criteria-based BMI. Thirteen candidate genes were genotyped using Agena^® MassARRAY and examined for association with pre-pregnancy obesity using multiple logistic regression analysis. The significant difference threshold was set at P value <0.05.

Results

Three hundred and twelve GDM women were included in this study; 60.9% and 44.2% of GDM patients were obese using Asian and International criteria-based BMI, respectively. GDM patients with AA or AG genotypes in specific SNP of brain-derived neurotrophic factor (BDNF) (G > A in rs6265) are more likely to be obese (adjusted odd ratio =2.209, 95% CI, 1.305, 3.739, P=0.003) compared to those who carry the GG genotype in the SNP adjusted for parity, underlying with asthma, heart disease, anaemia, education background in the International criteria-based BMI stratification group. On the other hand, there were no associations between other candidate genes (NRG1, FKBP5, RORA, OXTR, PLEKHG1, HTR2C, LHPP, SDK2, TEX51, EPHX2, NPY5R and ANO2) and maternal obesity.

Conclusions

In summary, BDNF rs6265 is significantly associated with pre-pregnancy obesity among GDM patients. The exact role of BDNF adjusted for diet intake and lifestyle factors merits further investigation.

There is no association between rs6296 and alcoholism: a meta-analysis

Previous studies have reported controversial results about the association between rs6296 and alcoholism. Thus, a meta-analysis was performed to further explore this association. A comprehensive search was conducted to identify relevant case-control or cohort studies (up to December 1, 2017). A fixed- or random-effect model was selected as a pooling method depending on the heterogeneity among studies. The heterogeneity was measured by Q test and I² statistic. The Harbord and Peters test was used to estimate publication bias. Fifteen English articles with 16 outcomes and 5,429 participants were included in this meta-analysis. A fixed-effect model was chosen, and the pooled result showed that rs6296 was not related to alcoholism (z = 1.93, p = .053). The Harbord and Peters test showed that there was no publication bias. This meta-analysis indicated that rs6296 may be not be significantly associated with alcoholism, which needs to be further confirmed by future research.

A review of the neurobiological underpinning of comorbid substance use and mood disorders

BACKGROUND

There is evidence that substance use disorders and other mental disorders may have shared biological mechanisms. However, the neurobiological basis of this comorbidity remains only partially explained. This review describes the historical evolution of the dual disorders concept and approach, and reviews the existing literature on neurobiological findings specifically regarding comorbid substance use and mood disorders.

METHODS

Searches were conducted using PubMed and Scopus in December 2017. A Boolean search was performed using combinations of "dual diagnosis" or "dual disorder" or "depression" or "bipolar" or "affective disorder" or "mood disorder" and "substance use" or "substance abuse" and "neurobiology" or "functional neuroimaging" or "genetics" or "neurotransmitters" or "neuroendocrinology" in the title or abstract, or as keywords, using no language restriction.

RESULTS

32 studies met the inclusion criteria. We found robust evidence for involvement of the neurotransmitters dopamine, GABA and glutamate and their receptors, as well as by the central corticotrophin-releasing hormone, hypothalamic-pituitary-adrenal axis activation, oxidative stress and inflammation. Recent studies focusing on neuroimaging and genetics have not shown consistent results.

LIMITATIONS

Only two search tools were used; most identified studies excluded the population of interest (comorbid mood and substance abuse disorders).

CONCLUSIONS

The neurobiological relevance for the occurrence of comorbid mood and substance abuse disorders has not been fully elucidated. Considering the high levels of individuals who experience comorbidity in these areas as well as the negative associated outcomes, this is clearly an area that requires further in-depth investigation. Furthermore, findings from this area can help to inform drug abuse prevention and intervention efforts, and especially how they relate to populations with psychiatric symptoms.

Prevalence of comorbid bipolar and substance use disorders in clinical settings, 1990-2015: Systematic review and meta-analysis

BACKGROUND

Comorbidity between substance use disorders (SUDs) and bipolar disorder (BD) is highly prevalent to the extent it may almost be regarded the norm. This systematic review and meta-analysis aimed to estimate the prevalence rates of SUDs in treatment seeking patients diagnosed with BD in both inpatient and outpatient settings.

METHODS

A comprehensive literature search of Medline, EMBASE, psychINFO and CINAHL databases was conducted from 1990 to 2015. Prevalence of co-morbid SUDs and BD were extracted and odds ratios (ORs) were calculated using random effects meta-analysis.

RESULTS

There were 151 articles identified by electronic searches that yielded 22 large, multi-site studies and 56 individual studies describing comorbid rates of SUDs amongst community dwelling, BD inpatients or outpatients. The SUDs with the highest prevalence in BD were alcohol use (42%) followed by cannabis use (20%) and other illicit drug use (17%). Meta-analysis showed males had higher lifetime risks of SUDs compared to females. BD and comorbid SUDS were associated with earlier age of onset and slightly more hospitalisations than non-users.

LIMITATIONS

The results do not take into account the possibility that individuals may have more than one comorbid disorder, such as having more than one SUD, anxiety disorder, or other combination. Some of the meta-analyses were based on relatively few studies with high rates of heterogeneity. Most included studies were cross-sectional and therefore causality cannot be inferred.

CONCLUSIONS

This systematic review shows comorbidity between SUDs and bipolar illness is highly prevalent in hospital and community-based samples. The prevalence of SUDs was similar in patients with bipolar I and bipolar II disorders. This study adds to the literature demonstrating that SUDs are common in BD and reinforces the need to provide better interventions and properly conducted treatment trials to reduce the burden conferred by comorbid SUD and BD.

Glutamatergic and HPA-axis pathway genes in bipolar disorder comorbid with alcohol- and substance use disorders

Glutamatergic neurotransmission has been shown to be dysregulated in bipolar disorder (BD), alcohol use disorder (AUD) and substance use disorder (SUD). Similarly, disruption in the hypothalamic-pituitary-adrenal (HPA)-axis has also been observed in these conditions. BD is often comorbid with AUD and SUD. The effects of the glutamatergic and HPA systems have not been extensively examined in individuals with BD-AUD and BD-SUD comorbidity. The aim of this investigation was to determine whether variants in the glutamatergic pathway and HPA-axis are associated with BD-AUD and BD-SUD comorbidity. The research cohort consisted of 498 individuals with BD type I from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). A subset of the cohort had comorbid current AUD and current SUD. A total of 1935 SNPs from both the glutamatergic and HPA pathways were selected from the STEP-BD genome-wide dataset. To identify population stratification, IBS clustering was performed using the program Plink 1.07. Single SNP association and gene-based association testing were conducted using logistic regression. A pathway analysis of glutamatergic and HPA genes was performed, after imputation using IMPUTE2. No single SNP was associated with BD-AUD or BD-SUD comorbidity after correction for multiple testing. However, from the gene-based analysis, the gene PRKCI was significantly associated with BD-AUD. The pathway analysis provided overall negative findings, although several genes including GRIN2B showed high percentage of associated SNPs for BD-AUD. Even though the glutamatergic and HPA pathways may not be involved in BD-AUD and BD-SUD comorbidity, PRKCI deserves further investigation in BD-AUD.

Possible involvement of the circadian pathway in alcohol use disorder in a South African adolescent cohort

Alcoholism has an estimated heritability of between 40 and 60% and it is thought that several genes of small effect may contribute to the risk of developing this disorder. Studies of the genetics of alcohol use disorder (AUD) may, however, be confounded by issues of comorbidity. The aim of this investigation was to assess associations between variants in a range of candidate genes and AUD in a unique sample of adolescents without comorbidity. Our cohort consisted of 80 adolescents with an AUD diagnosis and 80 matched controls of mixed ancestry ethnicity. An Illumina Infinium iSelect custom 6000 bead chip was used to genotype 5348 SNPs in 378 candidate genes. Association analysis, gene-based analysis and polygenic scoring were performed. There was no statistical association between any of the investigated SNPs and AUD after correction for multiple testing. However, from the gene-based analysis it was found that the circadian rhythm genes NR1D1 and BHLHE41 are associated with AUD. While preliminary, these data provide some evidence that the circadian pathway may be relevant to the pathophysiology of AUD. Study of early onset non-comorbid populations with AUD may be useful in identifying target genes for study in larger more representative samples.

DRD3 variation associates with early-onset heroin dependence, but not specific personality traits

Dopamine D3 receptor-mediated pathways are involved in the mechanism of addiction, and genetic factors play a role in the vulnerability to heroin dependence. The aim of this study was to examine whether the corresponding gene, DRD3, is associated with the development of heroin dependence and specific personality traits in HD patients. Eight polymorphisms in DRD3 were analyzed in 1067 unrelated Han Chinese subjects (566 heroin dependence patients and 501 controls). All participants were screened using the same assessment tool and all patients met the criteria for heroin dependence. A Tridimensional Personality Questionnaire was used to assess personality traits in 276 heroin dependence patients. In addition, heroin dependence patients were divided into 4 clinical subgroups based on age-of-onset and family history of substance abuse, to reduce the clinical heterogeneity. The rs6280 and rs9825563 variants showed association with the development of early-onset heroin dependence. The GTA haplotype frequency in the block (rs324029, rs6280, rs9825563) was significantly associated with early-onset heroin dependence (p=0.003). However, these significant associations were weaker after Bonferroni's correction. In addition, these DRD3 polymorphisms did not influence novelty seeking and harm avoidance scores in HD patients. DRD3 is possibly a genetic factor in the development of early-onset heroin dependence, but is not associated with specific personality traits in these patients among the Han Chinese population.

Prevalence, correlates, comorbidity and severity of bipolar disorder: results from the Singapore Mental Health Study

BACKGROUND

Bipolar disorder (BPD) is a serious mental disorder and a leading cause of premature mortality worldwide. Prevalence and risk factors of BPD have not been well studied in multi-ethnic Asian populations. The study aimed to establish the prevalence of BPD and examine the associated socio-demographic correlates, comorbidity, severity, impairment and treatment contact in the Singapore resident population.

METHODS

The Singapore Mental Health Study was a cross-sectional epidemiological survey of a nationally representative sample of the resident (citizens and permanent residents) population in Singapore. The diagnoses were established using the World Mental Health Composite International Diagnostic Interview version 3.0 (CIDI 3.0) diagnostic modules for lifetime and 12-month prevalence of select mental illnesses including BPD.

RESULTS

The lifetime and 12-month prevalence estimates for BPD were 1.2% and 0.6%, respectively. More than two-thirds (69.4%) of respondents with lifetime BPD had other lifetime mental disorders, and approximately half (52.6%) of respondents with lifetime BPD also had at least one chronic physical condition; chronic pain was the most prevalent comorbid condition.

LIMITATIONS

The data was based on respondents' self-report and there could be an element of recall bias and under-reporting. We also did not obtain information on mixed episodes and rapid cycling disorders.

CONCLUSIONS

The high comorbidity, clinical severity, and role impairment associated with BPD exert a heavy toll at an individual and societal level.

Do alcohol use disorders destabilize the course of bipolar disorder?

OBJECTIVES

To determine whether long-term data implicate a negative effect of alcohol-use disorders (AUDs) on time to remission, risk of mood episode recurrence, and risk of mood switch/cycling in patients with bipolar disorder (BD). The short-term temporal sequence between alcohol use and onset of mood episodes was also examined.

METHODS

A MEDLINE literature search was conducted for measurement-based reports of alcohol and course of bipolar disorder.

RESULTS

Twenty-three original data publications were identified. Three out of 5 studies addressing the impact of AUDs on recovery from a mood episode demonstrated that alcohol did not prolong index mood episodes of any type. Six out of 11 reports evaluating the relationship between alcohol and the long term risk of mood episode recurrences suggested that high levels of alcohol intake increase the risk of a mood recurrence. Five out of 7 studies evaluating the short-term temporal sequence of AUDs and development of mood episodes among BD patients found that increased alcohol use preceded the development of new mood episodes. Four out of 5 studies examining the association between alcohol and rapid cycling indicated that AUDs were associated with higher rates of rapid-cycling.

LIMITATIONS

We limited our review to studies that were large enough to perform statistical testing, which may have led us to overlook informative smaller studies.

CONCLUSIONS

Although alcohol does not seem to affect time to mood episode remission, alcohol use destabilizes the course of illness over the long run as evidenced by associations with more rapid cycling and mood episode recurrence.

Bipolar disorder and alcohol use disorder: a review

Bipolar disorder and alcohol use disorder represent a significant comorbid population, which is significantly worse than either diagnosis alone in presentation, duration, co-morbidity, cost, suicide rate, and poor response to treatment. They share some common characteristics in relation to genetic background, neuroimaging findings, and some biochemical findings. They can be treated with separate care, or ideally some form of integrated care. There are a number of pharmacotherapy trials, and psychotherapy trials that can aid program development. Post-treatment prognosis can be influenced by a number of factors including early abstinence, baseline low anxiety, engagement with an aftercare program and female gender. The future development of novel therapies relies upon increased psychiatric and medical awareness of the co-morbidity, and further research into novel therapies for the comorbid group.

Association of genetic copy number variations at 11 q14.2 with brain regional volume differences in an alcohol use disorder population

This study investigates the relationship between genetic copy number variations and brain volume differences in an alcohol use disorder (AUD) population. We hypothesized that copy number variations may influence subject's risk for alcohol use disorders through variations in regional gray and white matter brain volumes. Since genetic influences upon behavior are the result of many complicated interactions we focus on differences in brain volume as a putative intermediate phenotype between genetic variation and behavior. Copy number variation, alcohol use assessments and brain structural magnetic resonance images from 283 subjects, 199 male and 84 females who were enrolled in two AUD studies were obtained and analyzed using a combination of the Freesurfer image analysis suite and independent component analysis. Because brain volume varies by age we compared participant's volume variation with that derived from a control cohort of 75 subjects. In addition we also regressed out the possible brain volume changes induced by long term alcohol consumption. Small cerebral cortex, cerebellar and caudate along with large cerebral white matter and 5th ventricle volumes are shown to be significantly associated with increased AUD severity. When these volume variations are compared with control subject volumes; the variations seen in subjects with AUD are markedly different from normal aging effects. CNVs at 11 q14.2 are marginally (p < 0.05 uncorrected) correlated with such brain volume variations and the correlation holds true after controlling for long-term alcohol consumption; deletion carriers have smaller cerebral cortex, cerebellar, caudate and larger cerebral white matter and 5th ventricle volumes than insertion carriers or subjects with no variation in this region. Similarly, deletion carriers also demonstrate higher AUD severity scores than insertion carriers or subjects with no variation. The results presented here suggest that copy number variation and in particular the variation at chromosome 11 q14.2 may have an impact in brain volume variation, potentially influencing AUD behavior.