Quantitative genetic analysis of anxiety trait in bipolar disorder

The role of lithium treatment on comorbid anxiety symptoms in patients with bipolar depression

BACKGROUND

Comorbid anxiety is pervasive and carries an immense psychosocial burden for patients with bipolar disorder. Despite this, trials reporting anxiety-related outcomes in this population are uncommon, particularly with regards to monotherapies.

METHODS

Patients (n = 31) with both bipolar I or II disorder in current depressive episodes were enrolled in a six-week, open-label, single-center trial assessing the efficacy of lithium monotherapy in treating symptoms depression and comorbid anxiety. Patients were mostly medication-free and lithium-naïve at baseline.

RESULTS

Significant improvements in depression (HAMD) and anxiety (HAM-A) were observed at the six-week endpoint, with remission and response rates greater than 50%. There was a positive correlation between endpoint HAM-A scores and HAM-D scores, r = 0.80, (p < 0.01). Improvements were realized at low serum lithium concentrations (0.49 ± 0.20 mEq/L).

LIMITATIONS

Lack of placebo control and small sample size warrants validation in larger randomized studies.

CONCLUSIONS

Taken in the context of prior evidence, lithium may have an important role in treating comorbid anxiety in bipolar disorder, both as adjunct and monotherapy. Lower doses of lithium may provide equivalent efficacy and enhance tolerability and compliance.

Psychological predictors of bipolarity in panic disorder

BACKGROUND

Panic disorders frequently occur with affective disorders, particularly bipolar disorder. Patients with panic disorder and bipolar disorder are more likely to present with severe symptoms, such as high rates of suicidal behavior, poor symptomatic and functional recovery, and poor drug responses.

AIM

To investigate the psychological characteristics of panic disorder patients related to bipolarity.

METHODS

A total of 254 patients (136 men and 118 women, mean age = 33.48 ± 3.2 years) who were diagnosed with panic disorder were included in the study. Panic disorder with bipolarity (BP+) was defined as a score of ≥ 7 on the Korean version of the Mood Disorder Questionnaire (K-MDQ), and a score lower than 7 was considered as a panic disorder without bipolarity (BP-). Self-report questionnaires were analyzed to examine their association with bipolarity. Psychological tests used in the study were the Mood Disorder Questionnaire (MDQ), Panic Disorder Severity Scale, Beck Depression Inventory, State-Trait Anxiety Inventory (STAI), Temperament and Character Inventory (TCI), and Minnesota Multiphasic Personality Inventory (MMPI). Statistical analyses were performed to evaluate the correlation between bipolarity of panic disorder patients and various psychological test results indicative of psychological characteristics.

RESULTS

Patients with a K-MDQ score of 7 or more were considered to have a history of manic or hypomanic episodes (BP+ group, n = 128), while patients with K-MDQ scores below 7 were defined as those without bipolarity (BP- group, n = 126). The BP+ group were more likely to be unmarried (single 56.2% vs 44.4%, P = 0.008) and younger (30.78 ± 0.59 vs 37.11 ± 3.21, P < 0.001). Additionally, the BP+ group had significantly higher scores on psychological assessment scales, such as the hypochondriasis, psychopathic deviate, masculinity-femininity, psychasthenia, schizophrenia, and hypomania (Ma) in MMPI, and novelty seeking, harm avoidance and self-transcendence in TCI, and STAI (state and trait) compared to the BP- group. In logistic regression analysis, depression in MMPI, self-directedness in TCI, and age were negatively associated with MDQ score, meanwhile, Ma in MMPI and STAI (trait) were positively associated with MDQ score.

CONCLUSION

The result of this study suggests that almost 50% of patients with panic disorder are likely to have hypomanic or manic symptoms, and certain psychological factors are associated bipolarity in panic disorder.

Clinical and genetic validity of quantitative bipolarity

Research has yet to provide a comprehensive understanding of the genetic basis of bipolar disorder (BP). In genetic studies, defining the phenotype by diagnosis may miss risk-allele carriers without BP. The authors aimed to test whether quantitatively detected subclinical symptoms of bipolarity identifies a heritable trait that infers risk for BP. The Quantitative Bipolarity Scale (QBS) was administered to 310 Old Order Amish or Mennonite individuals from multigenerational pedigrees; 110 individuals had psychiatric diagnoses (20 BP, 61 major depressive disorders (MDD), 3 psychotic disorders, 26 other psychiatric disorders). Familial aggregation of QBS was calculated using the variance components method to derive heritability and shared household effects. The QBS score was significantly higher in BP subjects (31.5 ± 3.6) compared to MDD (16.7 ± 2.0), other psychiatric diagnoses (7.0 ± 1.9), and no psychiatric diagnosis (6.0 ± 0.65) (all p < 0.001). QBS in the whole sample was significantly heritable (h² = 0.46 ± 0.15, p < 0.001) while the variance attributed to the shared household effect was not significant (p = 0.073). When subjects with psychiatric illness were removed, the QBS heritability was similar (h² = 0.59 ± 0.18, p < 0.001). These findings suggest that quantitative bipolarity as measured by QBS can separate BP from other psychiatric illnesses yet is significantly heritable with and without BP included in the pedigrees suggesting that the quantitative bipolarity describes a continuous heritable trait that is not driven by a discrete psychiatric diagnosis. Bipolarity trait assessment may be used to supplement the diagnosis of BP in future genetic studies and could be especially useful for capturing subclinical genetic contributions to a BP phenotype.

Genome-wide QTL analysis for anxiety trait in bipolar disorder type I

BACKGROUND

Genetic studies have been consistent that bipolar disorder type I (BPI) runs in families and that this familial aggregation is strongly influenced by genes. In a preliminary study, we proved that anxiety trait meets endophenotype criteria for BPI.

METHODS

We assessed 619 individuals from the Central Valley of Costa Rica (CVCR) who have received evaluation for anxiety following the same methodological procedure used for the initial pilot study. Our goal was to conduct a multipoint quantitative trait linkage analysis to identify quantitative trait loci (QTLs) related to anxiety trait in subjects with BPI. We conducted the statistical analyses using Quantitative Trait Loci method (Variance-components models), implemented in Sequential Oligogenic Linkage Analysis Routines (SOLAR), using 5606 single nucleotide polymorphism (SNPs).

RESULTS

We identified a suggestive linkage signal with a LOD score of 2.01 at chromosome 2 (2q13-q14).

LIMITATIONS

Since confounding factors such as substance abuse, medical illness and medication history were not assessed in our study, these conclusions should be taken as preliminary.

CONCLUSIONS

We conclude that region 2q13-q14 may harbor a candidate gene(s) with an important role in the pathophysiology of BPI and anxiety.