Specificity in Etiology of Subtypes of Bipolar Disorder: Evidence From a Swedish Population-Based Family Study

Differences in clinical presentation between newly diagnosed bipolar I and II disorders: A naturalistic study

AIM

This naturalistic clinical study aims to investigate differences between newly diagnosed patients with bipolar type I (BDI) and bipolar type II (BDII) disorders in socio-demographic and clinical characteristics, affective symptoms, cognition, functioning and comorbidity with personality disorders.

METHODS

The BD diagnosis and type were confirmed using the Schedules for Clinical Assessment in Neuropsychiatry. Affective symptoms were assessed with the Young Mania Rating Scale, the Hamilton Depression Rating Scale, the Major Depressive Index, and the Altman Self-Rating Mania Scale. Functional impairment was assessed with the Functional Assessment Short Test. Cognitive impairment was evaluated by the Screen for Cognitive Impairment in Psychiatry and the Cognitive Complaints in Bipolar Disorder Rating Assessment. Finally, comorbid personality disorders were assessed with the Standardized Assessment of Personality-Abbreviated Scale and structured interview Structured Clinical Interview for DSM-disorders.

RESULTS

383 newly diagnosed patients were included (BDI: n = 125; BDII: n = 258). Against expectations, we found no more depressive symptoms in BDII compared with BDI nor any differences in cognitive, childhood trauma or overall functional impairment. The only difference was lower occupational impairment in the BDII group.

LIMITATIONS

The self-reported measures of cognitive difficulties and childhood trauma involved potential bias (recall or other). Despite BD being newly diagnosed a diagnostic delay was observed.

CONCLUSION

Patients newly diagnosed with BDII and BDI had similar burdens of depressive symptoms and cognitive and overall functional impairment, however patients with BDI had lower occupational functioning. No statistically significant difference was found in prevalence of comorbid personality disorders between patients with BDI and BDII.

White and gray matter alterations in bipolar I and bipolar II disorder subtypes compared with healthy controls - exploring associations with disease course and polygenic risk

Patients with bipolar disorder (BD) show alterations in both gray matter volume (GMV) and white matter (WM) integrity compared with healthy controls (HC). However, it remains unclear whether the phenotypically distinct BD subtypes (BD-I and BD-II) also exhibit brain structural differences. This study investigated GMV and WM differences between HC, BD-I, and BD-II, along with clinical and genetic associations. N = 73 BD-I, n = 63 BD-II patients and n = 136 matched HC were included. Using voxel-based morphometry and tract-based spatial statistics, main effects of group in GMV and fractional anisotropy (FA) were analyzed. Associations between clinical and genetic features and GMV or FA were calculated using regression models. For FA but not GMV, we found significant differences between groups. BD-I patients showed lower FA compared with BD-II patients (ptfce-FWE = 0.006), primarily in the anterior corpus callosum. Compared with HC, BD-I patients exhibited lower FA in widespread clusters (ptfce-FWE < 0.001), including almost all major projection, association, and commissural fiber tracts. BD-II patients also demonstrated lower FA compared with HC, although less pronounced (ptfce-FWE = 0.049). The results remained unchanged after controlling for clinical and genetic features, for which no independent associations with FA or GMV emerged. Our findings suggest that, at a neurobiological level, BD subtypes may reflect distinct degrees of disease expression, with increasing WM microstructure disruption from BD-II to BD-I. This differential magnitude of microstructural alterations was not clearly linked to clinical and genetic variables. These findings should be considered when discussing the classification of BD subtypes within the spectrum of affective disorders.

Childhood and adolescence outcomes in offspring to parents with bipolar disorder: the impact of lifetime parental comorbidity, parental sex, and bipolar subtype

BACKGROUND

Offspring of parents with bipolar disorder have increased risks of their own psychopathology. However, a large-scale survey of psychiatric, somatic, and adverse social outcomes up to adulthood, which could aid in prioritizing and tailoring prevention, is lacking. It also remains to clarify how risks are modified by other parental factors.

METHODS

Swedish population registers were linked to compare offspring having (N = 24,788) and not having (N = 247,880) a parent with bipolar disorder with respect to psychiatric diagnoses and psychotropic medication, birth-related and somatic conditions, social outcomes, accidents, suicide attempts, and mortality. Individuals were followed until age 18. We estimated the influence of lifetime parental psychiatric comorbidity, bipolar disorder subtype, and sex on outcomes.

RESULTS

Children of parents with bipolar disorder had 2-3 times higher risks of all psychiatric diagnoses, except for bipolar disorder, for which the risk was 11-fold. Significantly increased risks were also found for several somatic conditions, low school grades, criminal behavior, victimization, accidents, and suicidal behavior. Adjusting for lifetime parental psychiatric comorbidity attenuated most associations. Offspring of a parent with bipolar disorder type 2 had statistically significantly higher risks of attention deficit hyperactivity disorder, respiratory tract conditions, and accidents compared with offspring of a parent with bipolar disorder type 1. Offspring of mothers with bipolar disorder had higher risks of several psychiatric diagnoses, respiratory tract conditions, low school grades, and accidents compared with offspring of fathers with bipolar disorder. Having two parents with bipolar disorder entailed the highest risks of psychiatric outcomes in offspring.

CONCLUSIONS

Early intervention and family support are particularly warranted for the offspring of a parent with bipolar disorder in the presence of lifetime parental psychiatric comorbidity, when the parent has bipolar disorder type 2, or when the mother or both parents have bipolar disorder.

Premorbid intelligence quotient and school failure as risk markers for bipolar disorder and major depressive disorder

Mood disorders significantly impact global health, with MDD ranking as the second leading cause of disability in the United States and BD ranking 18th. Despite their prevalence and impact, the relationship between premorbid intelligence and the subsequent development of BD and MDD remains inconclusive. This study investigates the potential of premorbid Intelligence Quotient (IQ) and school failure frequency as risk factors for Bipolar Disorder (BD) and Major Depressive Disorder (MDD) in a birth cohort setting. We analyze data from the Pelotas population-based birth cohort study, comprising 3580 participants aged 22, who had no prior mood disorder diagnoses. Utilizing regression models and accounting for potential confounders, we assess the impact of IQ and school failure, measured at age 18, on the emergence of BD and MDD diagnoses at age 22, using individuals without mood disorders as comparators. Results reveal that lower IQ (below 70) at 18 is associated with an increased risk of BD (Adjusted Odds Ratio [AOR] 1.75, 95%CI: 1.00-3.09, p < 0.05), while higher IQ (above 120) is linked to MDD (AOR 2.16, 95%CI: 1.24-3.75, p < 0.001). Moreover, an elevated number of school failures is associated with increased BD risk (AOR 1.23, 95%CI: 1.11-1.41, p < 0.001), particularly for BD type 1 (AOR 1.36, 95% CI: 1.17-1.58, p < 0.001). These findings offer insights into the distinct premorbid intellectual characteristics of BD and MDD and contribute to a deeper understanding of their developmental trajectories, potentially informing the development of risk assessment tools for mood disorders.

Genetic Contribution to the Heterogeneity of Major Depressive Disorder: Evidence From a Sibling-Based Design Using Swedish National Registers

OBJECTIVE

Major depressive disorder (MDD) is highly heterogeneous. Standard typology partly captures the disorder's symptomatic heterogeneity, although whether it adequately captures etiological heterogeneity remains elusive. The aim of this study was to investigate the genetic characterization of MDD heterogeneity.

METHODS

Using Swedish patient register data on 1.5 million individuals, the authors identified 46,255 individuals with specialist-diagnosed MDD. Eighteen subgroups were identified based on nine comparison groups defined by clinical and psychosocial features, including severity, recurrence, comorbidities, suicidality, impairment, disability, care unit, and age at diagnosis. A sibling-based design and classic quantitative genetic models were applied to estimate heritability of MDD subgroups and genetic correlations between subgroups.

RESULTS

Estimates of heritability ranged from 30.5% to 58.3% across subgroups. The disabled and youth-onset subgroups showed significantly higher heritability (55.1%-58.3%) than the overall MDD sample (45.3%, 95% CI=43.0-47.5), and the subgroups with single-episode MDD and without psychiatric comorbidity showed significantly lower estimates (30.5%-34.4%). Estimates of genetic correlations between the subgroups within comparison groups ranged from 0.33 to 0.90. Seven of nine genetic correlations were significantly smaller than 1, suggesting differences in underlying genetic architecture. These results were largely consistent with previous work using genomic data.

CONCLUSIONS

The findings of differential heritability and partially distinct genetic components in subgroups provide important insights into the genetic heterogeneity of MDD and a deeper etiological understanding of MDD clinical subgroups.

Bipolar II Disorder: Understudied and Underdiagnosed

Despite its inclusion as a distinct entity in APA's Diagnostic and Statistical Manual of Mental Disorders since 1994, bipolar II disorder remains a surprisingly neglected psychiatric condition. Understudied and underrecognized, bipolar II disorder is often misdiagnosed and misunderstood, even by experienced clinicians. As a result, patients typically experience symptoms for more than 10 years before receiving the correct diagnosis. Incorrect diagnosis leads to incorrect treatment, including overuse of monoaminergic antidepressant medications, with resultant declines in functioning and worse quality of life. Perhaps because of its underrecognition, treatment studies of bipolar II disorder are limited, and, too often, results of bipolar I disorder studies are applied to bipolar II disorder, with no direct evidence supporting this practice. Bipolar II disorder is an understudied and unmet treatment challenge in psychiatry. In this review, the authors provide a broad overview of bipolar II disorder, including differential diagnosis, course of illness, comorbid conditions, and suicide risk. The authors summarize treatment studies specific to bipolar II disorder, identifying gaps in the literature. This review reveals similarities between bipolar I and bipolar II disorders, including risks of suicide and predominance of depression over the course of illness, but also differences between the phenotypes in treatment response, for example, to antidepressant medications.

Specificity of affective dynamics of bipolar and major depressive disorder

OBJECTIVE

Here, we examine whether the dynamics of the four dimensions of the circumplex model of affect assessed by ecological momentary assessment (EMA) differ among those with bipolar disorder (BD) and major depressive disorder (MDD).

METHODS

Participants aged 11-85 years (n = 362) reported momentary sad, anxious, active, and energetic dimensional states four times per day for 2 weeks. Individuals with lifetime mood disorder subtypes of bipolar-I, bipolar-II, and MDD derived from a semistructured clinical interview were compared to each other and to controls without a lifetime history of psychiatric disorders. Random effects from individual means, inertias, innovation (residual) variances, and cross-lags across the four affective dimensions simultaneously were derived from multivariate dynamic structural equation models.

RESULTS

All mood disorder subtypes were associated with higher levels of sad and anxious mood and lower energy than controls. Those with bipolar-I had lower average activation, and lower energy that was independent of activation, compared to MDD or controls. However, increases in activation were more likely to perpetuate in those with bipolar-I. Bipolar-II was characterized by higher lability of sad and anxious mood compared to bipolar-I and controls but not MDD. Compared to BD and controls, those with MDD exhibited cross-augmentation of sadness and anxiety, and sadness blunted energy.

CONCLUSION

Bipolar-I is more strongly characterized by activation and energy than sad and anxious mood. This distinction has potential implications for both specificity of intervention targets and differential pathways underlying these dynamic affective systems. Confirmation of the longer term stability and generalizability of these findings in future studies is necessary.

Bipolar disorder: Diagnosis, treatment and future directions

Bipolar disorder is a relatively common mental illness, characterised by recurrent episodes of mania (or hypomania) and major depression, and associated with a significant burden of morbidity and premature mortality. Physicians across all specialities are likely to encounter individuals with the condition within their clinical practice. This short review provides an up-to-date overview of the clinical features, epidemiology, pathophysiology, evidence-based management, prognosis and future directions for treatment and research in bipolar disorder. Aspects of cross-specialty relevance are highlighted, including the physical health burden associated with the condition, and the side effects and safety considerations of medication regimes used in bipolar disorder.

Differential characteristics of bipolar I and II disorders: a retrospective, cross-sectional evaluation of clinical features, illness course, and response to treatment

BACKGROUND

The distinction between bipolar I and bipolar II disorder and its treatment implications have been a matter of ongoing debate. The aim of this study was to examine differences between patients with bipolar I and II disorders with particular emphasis on the early phases of the disorders.

METHODS

808 subjects diagnosed with bipolar I (N = 587) or bipolar II disorder (N = 221) according to DSM-IV criteria were recruited between April 1994 and March 2022 from tertiary-level mood disorder clinics. Sociodemographic and clinical variables concerning psychiatric and medical comorbidities, family history, illness course, suicidal behavior, and response to treatment were compared between the bipolar disorder types.

RESULTS

Bipolar II disorder patients were more frequently women, older, married or widowed. Bipolar II disorder was associated with later "bipolar" presentation, higher age at first (hypo)mania and treatment, less frequent referral after a single episode, and more episodes before lithium treatment. A higher proportion of first-degree relatives of bipolar II patients were affected by major depression and anxiety disorders. The course of bipolar II disorder was typically characterized by depressive onset, early depressive episodes, multiple depressive recurrences, and depressive predominant polarity; less often by (hypo)mania or (hypo)mania-depression cycles at onset or during the early course. The lifetime clinical course was more frequently rated as chronic fluctuating than episodic. More patients with bipolar II disorder had a history of rapid cycling and/or high number of episodes. Mood stabilizers and antipsychotics were prescribed less frequently during the early course of bipolar II disorder, while antidepressants were more common. We found no differences in global functioning, lifetime suicide attempts, family history of suicide, age at onset of mood disorders and depressive episodes, and lithium response.

CONCLUSIONS

Differences between bipolar I and II disorders are not limited to the severity of (hypo)manic syndromes but include patterns of clinical course and family history. Caution in the use of potentially mood-destabilizing agents is warranted during the early course of bipolar II disorder.

Family environment and polygenic risk in the bipolar high-risk context

Background

The interaction of polygenic risk (PRS) and environmental effects on development of bipolar disorder (BD) is understudied, as are high-risk offspring perceptions of their family environment (FE). We tested the association of offspring-perceived FE in interaction with BD-PRS on liability for BD in offspring at high or low familial risk for BD.

Methods

Offspring of a parent with BD (oBD; n = 266) or no psychiatric disorders (n = 174), aged 12-21 at recruitment, participated in the US and Australia. Empirically-derived profiles of FE classified offspring by their perceived levels of familial cohesion, flexibility, and conflict. Offspring BD-PRS were derived from Psychiatric Genomics Consortium BD-GWAS. Lifetime DSM-IV bipolar disorders were derived from the Schedule for Affective Disorders and Schizophrenia for School-Aged Children. We used a novel stepwise approach for latent class modeling with predictors and distal outcomes.

Results

Fifty-two offspring were diagnosed with BD. For those with well-functioning FE (two-thirds of the sample), higher BD-PRS tracked positively with liability for BD. However, for those with high-conflict FEs, the relationship between BD-PRS and liability to BD was negative, with highest risk for BD observed with lower BD-PRS. In exploratory analyses, European-ancestry offspring with BD had elevated history of suicidal ideation in high-conflict FE compared to well-functioning-FE, and of suicide attempt with low-BD-PRS and high-conflict FE.

Conclusions

The data suggest that the relationship of BD-PRS and offspring liability for BD differed between well-functioning versus high-conflict FE, potentially in line with a multifactorial liability threshold model and supporting future study of and interventions improving family dynamics.

Diagnosis and management of bipolar disorders

Bipolar disorders (BDs) are recurrent and sometimes chronic disorders of mood that affect around 2% of the world's population and encompass a spectrum between severe elevated and excitable mood states (mania) to the dysphoria, low energy, and despondency of depressive episodes. The illness commonly starts in young adults and is a leading cause of disability and premature mortality. The clinical manifestations of bipolar disorder can be markedly varied between and within individuals across their lifespan. Early diagnosis is challenging and misdiagnoses are frequent, potentially resulting in missed early intervention and increasing the risk of iatrogenic harm. Over 15 approved treatments exist for the various phases of bipolar disorder, but outcomes are often suboptimal owing to insufficient efficacy, side effects, or lack of availability. Lithium, the first approved treatment for bipolar disorder, continues to be the most effective drug overall, although full remission is only seen in a subset of patients. Newer atypical antipsychotics are increasingly being found to be effective in the treatment of bipolar depression; however, their long term tolerability and safety are uncertain. For many with bipolar disorder, combination therapy and adjunctive psychotherapy might be necessary to treat symptoms across different phases of illness. Several classes of medications exist for treating bipolar disorder but predicting which medication is likely to be most effective or tolerable is not yet possible. As pathophysiological insights into the causes of bipolar disorders are revealed, a new era of targeted treatments aimed at causal mechanisms, be they pharmacological or psychosocial, will hopefully be developed. For the time being, however, clinical judgment, shared decision making, and empirical follow-up remain essential elements of clinical care. This review provides an overview of the clinical features, diagnostic subtypes, and major treatment modalities available to treat people with bipolar disorder, highlighting recent advances and ongoing therapeutic challenges.

Bipolar I and bipolar II subtypes in older age: Results from the Global Aging and Geriatric Experiments in Bipolar Disorder (GAGE-BD) project

OBJECTIVES

The distinction between bipolar I disorder (BD-I) and bipolar II disorder (BD-II) has been a topic of long-lasting debate. This study examined differences between BD-I and BD-II in a large, global sample of OABD, focusing on general functioning, cognition and somatic burden as these domains are often affected in OABD.

METHODS

Cross-sectional analyses were conducted with data from the Global Aging and Geriatric Experiments in Bipolar Disorder (GAGE-BD) database. The sample included 963 participants aged ≥50 years (714 BD-I, 249 BD-II). Sociodemographic and clinical factors were compared between BD subtypes including adjustment for study cohort. Multivariable analyses were conducted with generalized linear mixed models (GLMMs) and estimated associations between BD subtype and (1) general functioning (GAF), (2) cognitive performance (g-score) and (3) somatic burden, with study cohort as random intercept.

RESULTS

After adjustment for study cohort, BD-II patients more often had a late onset ≥50 years (p = 0.008) and more current severe depression (p = 0.041). BD-I patients were more likely to have a history of psychiatric hospitalization (p < 0.001) and current use of anti-psychotics (p = 0.003). Multivariable analyses showed that BD subtype was not related to GAF, cognitive g-score or somatic burden.

CONCLUSION

BD-I and BD-II patients did not differ in terms of general functioning, cognitive impairment or somatic burden. Some clinical differences were observed between the groups, which could be the consequence of diagnostic definitions. The distinction between BD-I and BD-II is not the best way to subtype OABD patients. Future research should investigate other disease specifiers in this population.

Cohort profile: the Swedish National Quality Register for bipolar disorder(BipoläR)

PURPOSE

The Swedish National Quality Register for bipolar affective disorder, BipoläR, was established in 2004 to provide nationwide indicators for quality assessment and development in the clinical care of individuals with bipolar spectrum disorder. An ancillary aim was to provide data for bipolar disorder research.

PARTICIPANTS

Inclusion criteria for registration in BipoläR is a diagnosis of bipolar spectrum disorder (ICD codes: F25.0, F30.1-F30.2, F30.8-F31.9, F34.0) and treatment at an outpatient clinic in Sweden. BipoläR collects data from baseline and annual follow-up visits throughout Sweden. Data is collected using questionnaires administered by healthcare staff. The questions cover sociodemographic, diagnostic, treatment, outcomes and patient reported outcome variables. The register currently includes 39 583 individual patients with a total of 75 423 baseline and follow-up records.

FINDINGS TO DATE

Data from BipoläR has been used in several peer-reviewed publications. Studies have provided knowledge on effectiveness, side effects and use of pharmacological and psychological treatment in bipolar disorder. In addition, findings on the diagnosis of bipolar disorder, risk factors for attempted and completed suicide and health economics have been reported. The Swedish Bipolar Collection project has contributed to a large number of published studies and provides important information on the genetic architecture of bipolar disorder, the impact of genetic variation on disease characteristics and treatment outcome.

FUTURE PLANS

Data collection is ongoing with no fixed end date. Currently, approximately 5000 new registrations are added each year. Cohort data are available via a formalised request procedure from Centre of Registers Västra Götaland (e-mail: registercentrum@vgregion.se). Data requests for research purposes require an entity responsible for the research and an ethical approval.

Characterizing the polygenic overlaps of bipolar disorder subtypes with schizophrenia and major depressive disorder

BACKGROUND

Large-scale studies have shown that bipolar I disorder (BD-I) and bipolar II disorder (BD-II) have differences in genetic association with schizophrenia (SCZ) and major depressive disorder (MDD). However, the underlying shared genetic architectures between BD subtypes and both SCZ and MDD remain largely unknown.

METHODS

We applied univariate and bivariate causal mixture models (MiXeR) to estimate the polygenicity and polygenic overlaps on large GWASs summary statistics of BD-I (n = 25,060), BD-II (n = 6781), SCZ (n = 69,369) and MDD (n = 170,756). Then, conjunctional false discovery rate approach was used to identify specific shared genetic loci between BD subtypes and both SCZ and MDD.

RESULTS

Univariate MiXeR revealed that BD-II was substantially more polygenic (22.37 K causal variants) as compared to BD-I, SCZ and MDD (7.87-12.43 K causal variants). Bivariate MiXeR revealed substantial polygenic overlaps between BD-I and SCZ (Dice-coefficient = 0.83) and between BD-I and MDD (Dice-coefficient = 0.76), which are beyond the genetic correlation (rg = 0.71 and 0.36). Conjunctional FDR analysis identified 236 distinct shared loci between BD-I and BD-II (2 loci), BD-I and SCZ (227 loci), BD-I and MDD (19 loci), BD-II and SCZ (1 locus), and BD-II and MDD (3 loci). Most of these shared loci have concordant effect directions among BD subtypes, SCZ and MDD.

LIMITATIONS

The bivariate MiXeR model was not applied for the BD-II because of insufficient power and inadequate model fit.

CONCLUSIONS

These findings provide evidence for extensive polygenic effects across BD subtypes, SCZ and MDD, which further our understanding of the potential genetic basis for the comorbid symptoms across these disorders.

Differences in network properties of the structural connectome in bipolar and unipolar depression

BACKGROUND

Differentiation between Bipolar Disorder Depression (BDD) and Unipolar Major Depressive Disorder (MDD) is critical to clinical practice. This study investigated machine learning classification of BDD and MDD using graph properties of Diffusion-weighted Imaging (DWI)-based structural connectome.

METHODS

This study included a large number of medication-free (N =229) subjects: 60 BDD, 95 MDD, and 74 Healthy Control (HC) subjects. DWI probabilistic tractography was performed to create Fractional Anisotropy (FA) and Total Streamline (TS)-based structural connectivity matrices. Global and nodal graph properties were computed from these matrices and tested for group differences. Next, using identified graph properties, machine learning classification (MLC) between BDD, MDD, MDD with risk factors for developing BD (MDD+), and MDD without risk factors for developing BD (MDD-) was conducted.

RESULTS

Communicability Efficiency of the left superior frontal gyrus (SFG) was significantly higher in BDD vs. MDD. In particular, Communicability Efficiency using TS-based connectivity in the left SFG as well as FA-based connectivity in the right middle anterior cingulate area was higher in the BDD vs. MDD- group. There were no significant differences in graph properties between BDD and MDD+. Direct comparison between MDD+ and MDD- showed differences in Eigenvector Centrality (TS-based connectivity) of the left middle frontal sulcus. Acceptable Area Under Curve (AUC) for classification were seen between the BDD and MDD- groups, and between the MDD+ and MDD- groups, using the differing graph properties.

CONCLUSION

Graph properties of DWI-based connectivity can discriminate between BDD and MDD subjects without risk factors for BD.

Association of Etiological Factors for Hypomanic Symptoms, Bipolar Disorder, and Other Severe Mental Illnesses

IMPORTANCE

Subsyndromal hypomanic symptoms are relatively common in the general population and are linked to the onset of bipolar disorder. Little is known about their etiology and whether this is shared with the etiology of bipolar disorder or other mental illnesses.

OBJECTIVE

To examine the genetic and environmental architecture of hypomanic symptoms in a nonclinical youth sample and compare estimates at varying severity levels and their association with diagnosed bipolar disorder.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used phenotypic and genetic data from the Child and Adolescent Twin Study in Sweden and included individuals with International Statistical Classification of Diseases and Related Health Problems, Tenth Revision diagnosis of psychiatric disorders from national registries for residents of Sweden. Associations between hypomania and polygenic risk scores for bipolar disorder, major depressive disorder and schizophrenia were also investigated. Analysis began November 2018 and ended October 2021.

MAIN OUTCOMES AND MEASURES

Hypomanic symptoms were assessed using the parent-rated Mood Disorders Questionnaire when the twins were aged 18 years. Bipolar disorder diagnosis and/or lithium prescription were ascertained from national registries for residents of Sweden. Polygenic risk scores for psychiatric disorders were calculated using independent discovery genetic data.

RESULTS

A total of 8568 twin pairs aged 18 years (9381 [54.7%] female) were included in the study. The hypomania heritability estimate was 59% (95% CI, 52%-64%) for male individuals and 29% (95% CI, 16%-44%) for female individuals. Unique environmental factors accounted for 41% (95% CI, 36%-47%) of the hypomania variance in male individuals and 45% (95% CI, 40%-50%) in female individuals. Shared environmental factors were only detected for female individuals and explained 26% (95% CI, 13%-38%) of the variance. The heritability estimates were fairly consistent across different hypomania severity groups. Moderate genetic (0.40; 95% CI, 0.21-0.58) and shared environmental (0.41; 95% CI, 0.03-0.75) correlations between hypomania and diagnosed bipolar disorder were found. Hypomania was significantly associated with the polygenic risk scores for schizophrenia (β = 0.08; SE = 0.026; P = .002) and major depressive disorder (β = 0.09; SE = 0.027; P = .001) but not bipolar disorder (β = 0.017; SE = 0.03; P = 0.57) (bipolar disorder I [β = 0.014; SE = 0.029; P = .64] or bipolar disorder II [β = 0.045; SE = 0.027; P = .10]).

CONCLUSIONS AND RELEVANCE

Higher heritability for hypomania was found for male compared with female individuals. The results highlight the shared etiologies between hypomanic symptoms, bipolar disorder, major depression, and schizophrenia in youths. Future research should focus on identifying specific shared genetic and environmental factors. These findings support a possible dimensional model of bipolar disorder, with hypomania representing a continuous trait underlying the disorder.

Schema Therapy for Patients with Bipolar Disorder: Theoretical Framework and Application

Bipolar disorder (BD) is a severe mood disorder characterized by episodes of depression and hypomania or mania. Despite its primarily biological roots, the onset and course of the disorder have also been related to psychosocial factors such as early adverse experiences and related maladaptive schemas. Several researchers proposed a schema therapeutic model to treat patients with BD. In this paper, we further develop the theoretical model and elaborate on seven elements that were found effective in the psychosocial interventions with individuals with BD: monitoring mood and early symptoms of relapse, recognizing and management of stressful situations and interpersonal conflicts, creating a relapse prevention plan, stabilizing the sleep/wake cycle and daily routine, encouraging the use of medication, and reducing self-stigma and substance use. Apart from that, we describe the elements of the schema work with patients who suffer from BD. Illustrative clinical cases accompany the theoretical framework. The research of the schema therapy with patients with severe mental illnesses has only recently started developing. The presented paper also aims to encourage further research in this area and highlight potentially beneficial research goals.

Examining the association between childhood autistic traits and adolescent hypomania: a longitudinal twin study

BACKGROUND

There is evidence that autism spectrum disorders (ASDs) co-occur with bipolar disorder (BD) relatively frequently. Individuals with BD often report symptoms of mania and hypomania during adolescence, prior to the age of onset for BD. It is unknown whether these symptoms are associated with ASDs. We examined whether diagnoses of ASDs and autistic traits were associated with hypomania in a large, population-based Swedish twin sample.

METHODS

Parental structured interviews assessed autistic traits, and were used to assign screening diagnoses of ASDs, when twins were aged 9 or 12 (N = 13 533 pairs). Parents then completed questionnaires assessing hypomania when the twins were aged 15 and 18 (N = 3852 pairs at age 15, and 3013 pairs at age 18). After investigating the phenotypic associations between these measures, we used the classical twin design to test whether genetic and environmental influences on autistic traits influence variation in adolescent hypomania.

RESULTS

Autistic traits and ASD diagnoses in childhood were associated with elevated scores on the measures of adolescent hypomania. Twin analyses indicated that 6-9% of the variance in hypomania was explained by genetic influences that were shared with autistic traits in childhood. When repeating these analyses for specific autistic trait domains, we found a stronger association between social interaction difficulties and hypomania than for other autistic trait domains.

CONCLUSIONS

These results indicate a genetic link between autistic traits and hypomania in adolescence. This adds to the growing evidence base of genetic factors associated with ASDs showing links with psychiatric outcomes across childhood and into adulthood.

Limited Genetic Overlap Between Overt Hashimoto's Thyroiditis and Graves' Disease in Twins: A Population-based Study

CONTEXT

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are known to coaggregate in families, but the magnitude and nature of a shared etiology is unknown.

OBJECTIVES

To estimate the shared genetic influence on overt HT and GD and to examine if the heritability differs between men and women.

DESIGN, SETTING, AND PATIENTS

We used national health registries to identify cases of HT and GD in a cohort of 110 814 Swedish twins. By comparing intra-class and cross-twin cross-trait correlations in dizygotic and monozygotic twins, we calculated heritability and the proportions thereof shared between the diseases. Univariate estimates of heritability were calculated by sex.

RESULTS

The heritability for HT and GD was 65% (95% CI, 61-70) and 63% (95% CI, 55-72), respectively. The genetic correlation was 0.35 (95% CI, 0.20-0.50) and shared genetic effects accounted for 8% of the variance for both HT and GD. Univariate heritability was significantly higher in men than in women for HT (90% vs 60%, P < 0.001) but not for GD (79% vs 63%, P = 0.085).

CONCLUSIONS

From a genetic perspective, HT and GD appear to be only modestly related diseases. Hence, the term "autoimmune thyroid disease," used to cluster these disorders, may have limited validity in a genetic context. Moreover, the mechanisms contributing to HT are partly different for the sexes, with genetic components more important in men.

Clinical and genetic differences between bipolar disorder type 1 and 2 in multiplex families

The two major subtypes of bipolar disorder (BD), BD-I and BD-II, are distinguished based on the presence of manic or hypomanic episodes. Historically, BD-II was perceived as a less severe form of BD-I. Recent research has challenged this concept of a severity continuum. Studies in large samples of unrelated patients have described clinical and genetic differences between the subtypes. Besides an increased schizophrenia polygenic risk load in BD-I, these studies also observed an increased depression risk load in BD-II patients. The present study assessed whether such clinical and genetic differences are also found in BD patients from multiplex families, which exhibit reduced genetic and environmental heterogeneity. Comparing 252 BD-I and 75 BD-II patients from the Andalusian Bipolar Family (ABiF) study, the clinical course, symptoms during depressive and manic episodes, and psychiatric comorbidities were analyzed. Furthermore, polygenic risk scores (PRS) for BD, schizophrenia, and depression were assessed. BD-I patients not only suffered from more severe symptoms during manic episodes but also more frequently showed incapacity during depressive episodes. A higher BD PRS was significantly associated with suicidal ideation. Moreover, BD-I cases exhibited lower depression PRS. In line with a severity continuum from BD-II to BD-I, our results link BD-I to a more pronounced clinical presentation in both mania and depression and indicate that the polygenic risk load of BD predisposes to more severe disorder characteristics. Nevertheless, our results suggest that the genetic risk burden for depression also shapes disorder presentation and increases the likelihood of BD-II subtype development.

Personalized estimates of morphometric similarity in bipolar disorder and schizophrenia

Bipolar disorder and schizophrenia are associated with brain morphometry alterations. This study investigates inter-individual variability in brain structural profiles, both within diagnostic groups and between patients and healthy individuals. Brain morphometric measures from three independent samples of patients with schizophrenia (n = 168), bipolar disorder (n = 122), and healthy individuals (n = 180) were modeled as single vectors to generated individualized profiles of subcortical volumes and regional cortical thickness. These profiles were then used to compute a person-based similarity index (PBSI) for subcortical volumes and for regional cortical thickness, to quantify the within-group similarity of the morphometric profile of each individual to that of the other participants in the same diagnostic group. There was no effect of diagnosis on the PBSI for subcortical volumes. In contrast, compared to healthy individuals, the PBSI for cortical thickness was lower in patients with schizophrenia (effect size = 0.4, p ≤ 0.0002), but not in patients with bipolar disorder. The results were robust and reproducible across samples. We conclude that disease mechanisms for these disorders produce modest inter-individual variations in brain morphometry that should be considered in future studies attempting to cluster patients in subgroups.

Person-based similarity in brain structure and functional connectivity in bipolar disorder

BACKGROUND

Bipolar disorder shows significant variability in clinical presentation. Here we adopt a personalized approach to quantify the brain structural and functional similarity of each individual patient to other patients and to healthy individuals.

METHODS

Brain morphometric and resting-state functional connectivity measures from two independent samples of patients with bipolar disorder and healthy individuals (total number of participants=215) were modeled as single vectors to generated individualized morphometric and connectivity profiles. These profiles were then used to compute a person-based similarity indices which quantified the similarity in neuroimaging profiles amongst patients and between patients and health individuals.

RESULTS

The morphometric and connectivity profiles of patients showed within-diagnosis similarity which was comparable to that observed in healthy individuals. They also showed minimal deviance from those of healthy individuals; the correlation between the profiles of patients and healthy individuals was high (range: 0.71-0.94, p<10^-5). The degree of similarity between imaging profiles was associated with IQ (for cortical thickness) and age (functional integration) rather than clinical variables. Patients who were prescribed lithium, compared to those who were not, showed greater similarity to healthy individuals in terms of network integration (t = 2.2, p = 0.03).

LIMITATIONS

We focused on patients with Bipolar disorder, type I only.

CONCLUSIONS

High inter-individual similarity in neuroimaging profiles was observed amongst patients with bipolar disorder and between patients and healthy individuals. We infer that brain alterations associated with bipolar disorder may be nested within the normal biological diversity consistent with the high prevalence of mood symptoms in the general population.

Sick leave due to back pain, common mental disorders and disability pension: Common genetic liability

BACKGROUND

Back pain and common mental disorders are often comorbid and known risk factors for future disability pension. However, the reason for the covariation is not known. The aim was to investigate the common genetic and environmental influences on the covariation between sick leave due to back pain, sick leave due to common mental disorders and disability pension.

METHODS

Register data from the Swedish Social Insurance Agency on sick leave due to back pain, common mental disorders and disability pension between 2005 and 2018, in a population-based sample of 56,686 working age twins was used to construct biometric twin models to calculate if the covariation between the traits were due to Additive (A) or Dominant (D) genetic factors, Common environmental factors (C) or unique Environmental factors (E), for women and men.

RESULTS

The phenotypic correlations ranged between 0.17 and 0.25. A common factor common pathway AE model fitted best for both women and men. The latent underlying common factor, that explained the covariation was mostly explained by genetic factors (87% for women and 90% for men). Each trait was also influenced by its own unique genetic and unique environment factors. A higher heritability was found for disability pension than for sick leave.

CONCLUSIONS

The covariation between sick leave due to back pain and common mental disorders, and disability pension were mostly explained by common genetic factors, while the unique variation in each trait was influenced by both genetic and environmental factors not shared within the twin pairs.

SIGNIFICANCE

A common genetic liability seems to be of importance in the comorbidity of sick leave due to back pain and common mental disorders and the transition to disability pension, both among women and men. However, the proportion in each trait that was explained by genetic factors was somewhat higher for men than for women in all traits. This may be of importance to consider in intervention or prevention efforts.

Markers of Regenerative Processes in Patients with Bipolar Disorder: A Case-control Study

Progress in medical science has allowed the discovery of many factors affecting the pathogenesis of bipolar disorder, and among the most recent research directions are found regenerative and inflammatory processes. The role of regenerative processes remains particularly poorly explored, but available data encourage further research, which may explain the pathogenesis of bipolar disorder (BD). The aim of this study was to evaluate the mobilization of stem cells into peripheral blood, in patients with bipolar disorder during stable phase, not treated with lithium salts. The study included 30 unrelated individuals with the diagnosis of bipolar disorder, with disease duration of at least 10 years, not treated with lithium salts for at least five years prior to the study. The control group consisted of 30 healthy subjects, matched for age, sex, body mass index (BMI), origin, socio-demographic factors and nicotine use. Blood samples underwent cytometric analyses to assess concentrations of: Very Small Embryonic Like (VSEL) CD34+, VSEL AC133+, HSC CD34+, HSC AC133+. There were no significant differences in stem cell levels between patients with BD and healthy controls. However, the level of VSEL cells AC133 + was significantly higher in type I BD patients compared to healthy controls. Our results indicate a disturbance in regenerative processes in patients with bipolar disorder.

Investigating gender-specific effects of familial risk for attention-deficit hyperactivity disorder and other neurodevelopmental disorders in the Swedish population

BACKGROUND

Many psychiatric disorders show gender differences in prevalence. Recent studies suggest that female patients diagnosed with anxiety and depression carry more genetic risks related to attention-deficit hyperactivity disorder (ADHD) compared with affected males.

AIMS

In this register-based study, we aimed to test whether female patients who received clinical diagnoses of anxiety, depressive, bipolar and eating disorders are at higher familial risk for ADHD and other neurodevelopmental disorders, compared with diagnosed male patients.

METHOD

We analysed data from a record-linkage of several Swedish national registers, including 151 025 sibling pairs from 103 941 unique index individuals diagnosed with anxiety, depressive, bipolar or eating disorders, as well as data from 646 948 cousin pairs. We compared the likelihood of having a relative diagnosed with ADHD/neurodevelopmental disorders in index males and females.

RESULTS

Female patients with anxiety disorders were more likely than affected males to have a brother with ADHD (odd ratio (OR) = 1.13, 95% CI 1.05-1.22). Results for broader neurodevelopmental disorders were similar and were driven by ADHD diagnoses. Follow-up analyses revealed similar point estimates for several categories of anxiety disorders, with the strongest effect observed for agoraphobia (OR = 1.64, 95% CI 1.12-2.39). No significant associations were found in individuals with depressive, bipolar or eating disorders, or in cousins.

CONCLUSIONS

These results provide modest support for the possibility that familial/genetic risks for ADHD may show gender-specific phenotypic expression. Alternatively, there could be gender-specific biases in diagnoses of anxiety and ADHD. These factors could play a small role in the observed gender differences in prevalence of ADHD and anxiety.

Trends in the incidence and DALYs of bipolar disorder at global, regional, and national levels: Results from the global burden of Disease Study 2017

The objective of this study is to assess the global, regional, and national burden of bipolar disorder (BPD) from 1990 to 2017, by gender, age, and social-demographic index (SDI) from the 2017 Global Burden of Disease (GBD) study. We collected detailed information from GBD on the numbers of incidence cases and disability-adjusted life years (DALYs), age-standardized incidence rate (ASIR), and age-standardized DALYs rate (ASDR) during 1990-2017. Estimated annual percentage changes (EAPCs) were calculated to assess ASIR and ASDR trends. GBD data estimated that BPD incidences increased by 47.74%, from 3.06 million in 1990 to 4.53 million in 2017, and the DALYs increased by 54.4%, from 6.02 million in 1990 to 9.29 million in 2017. Over the 28-year period between 1990 and 2017, the ASIR and ASDR increased only slightly (EAPC = 0.14 and 0.05 for ASIR and ASDR, respectively). Subjects aged 10-19 years contributed the most to the total number of incidence cases, while those aged 20-44 years contributed the most to the number of DALYs. The ASIR and ASDR were highest in tropical Latin America and lowest in East Asia. Areas in the lowest sociodemographic index (SDI) quintile showed the highest ASIR (about 64/100,000), and those in the highest SDI quintile showed the highest ASDR (about 140/100,000). In conclusion, while the ASIR and ASDR due to BPD have been stable, the absolute incidence and DALYs remain high, which represents an increasing burden on health-care systems.

On the diagnostic and neurobiological origins of bipolar disorder

Psychiatry is constructed around a taxonomy of several hundred diagnoses differentiated by nuances in the timing, co-occurrence, and severity of symptoms. Bipolar disorder (BD) is notable among these diagnoses for manic, depressive, and psychotic symptoms all being core features. Here, we trace current understanding of the neurobiological origins of BD and related diagnoses. To provide context, we begin by exploring the historical origins of psychiatric taxonomy. We then illustrate how key discoveries in pharmacology and neuroscience gave rise to a generation of neurobiological hypotheses about the origins of these disorders that facilitated therapeutic innovation but failed to explain disease pathogenesis. Lastly, we examine the extent to which genetics has succeeded in filling this void and contributing to the construction of an objective classification of psychiatric disturbance.

Clinical phenotype and genetic risk factors for bipolar disorder with binge eating: an update

Introduction: Clinical and genetic study of psychiatric conditions has underscored the co-occurrence of complex phenotypes and the need to refine them. Bipolar Disorder (BD) and Binge Eating (BE) behavior are common psychiatric conditions that have high heritability and high co-occurrence, such that at least one quarter of BD patients have BE (BD + BE). Genetic studies of BD alone and of BE alone suggest complex polygenic risk models, with many genetic risk loci yet to be identified. Areas covered: We review studies of the epidemiology of BD+BE, its clinical features (cognitive traits, psychiatric comorbidity, and role of obesity), genomic studies (of BD, eating disorders (ED) defined by BE, and BD + BE), and therapeutic implications of BD + BE. Expert opinion: Subphenotyping of complex psychiatric disorders reduces heterogeneity and increases statistical power and effect size; thus, it enhances our capacity to find missing genetic (and other) risk factors. BD + BE has a severe clinical picture and genetic studies suggests a distinct genetic architecture. Differential therapeutic interventions may be needed for patients with BD + BE compared with BD patients without BE. Recognizing the BD + BE subphenotype is an example of moving towards more precise clinical and genetic entities.

Differences in Psychopathology between Offspring of Parents with Bipolar I Disorder and Those with Bipolar II Disorder: A Cross-Sectional Study

OBJECTIVE

The aim of this study was to evaluate differences in psychopathology between offspring of parents with bipolar I disorder (BP-I) and those with bipolar II disorder (BP-II).

METHODS

The sample included 201 offspring between 6 and 17 years of age who had at least one parent with BP-I or BP-II. The offspring were diagnostically evaluated using the Korean Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version. Psychopathology and Clinical characteristics were evaluated, including lifetime DSM-5 diagnoses, depression, and childhood trauma. Lifetime DSM-5 diagnoses were also compared between schoolchildren aged 6 to 11 years and adolescents aged 12 to 17 years.

RESULTS

In lifetime DSM-5 diagnoses, offspring of parents with BP-I had significantly increased risk of developing MDD and BP-I than those with BP-II. Regarding clinical characteristics, ADHD rating scale and childhood trauma scale were significantly higher in offspring of parents with BP-I than that in those with BP-II.

CONCLUSION

The present study supports that BP-I may be etiologically distinct from BP-II by a possible genetic liability. Our findings indicate that additional research related to bipolar offspring is needed to enhance understanding of differences between BP-I and BP-II.

Fronto-limbic dysconnectivity leads to impaired brain network controllability in young people with bipolar disorder and those at high genetic risk

Recent investigations have used diffusion-weighted imaging to reveal disturbances in the neurocircuitry that underlie cognitive-emotional control in bipolar disorder (BD) and in unaffected siblings or children at high genetic risk (HR). It has been difficult to quantify the mechanism by which structural changes disrupt the superimposed brain dynamics, leading to the emotional lability that is characteristic of BD. Average controllability is a concept from network control theory that extends structural connectivity data to estimate the manner in which local neuronal fluctuations spread from a node or subnetwork to alter the state of the rest of the brain. We used this theory to ask whether structural connectivity deficits previously observed in HR individuals (n = 84, mean age 22.4), patients with BD (n = 38, mean age 23.9), and age- and gender-matched controls (n = 96, mean age 22.6) translate to differences in the ability of brain systems to be manipulated between states. Localized impairments in network controllability were seen in the left parahippocampal, left middle occipital, left superior frontal, right inferior frontal, and right precentral gyri in BD and HR groups. Subjects with BD had distributed deficits in a subnetwork containing the left superior and inferior frontal gyri, postcentral gyrus, and insula (p = 0.004). HR participants had controllability deficits in a right-lateralized subnetwork involving connections between the dorsomedial and ventrolateral prefrontal cortex, the superior temporal pole, putamen, and caudate nucleus (p = 0.008). Between-group controllability differences were attenuated after removal of topological factors by network randomization. Some previously reported differences in network connectivity were not associated with controllability-differences, likely reflecting the contribution of more complex brain network properties. These analyses highlight the potential functional consequences of altered brain networks in BD, and may guide future clinical interventions.

•

Control theory estimates how neuronal fluctuations spread from local networks.

•

We compare brain controllability in bipolar disorder and their high-risk relatives.

•

These groups have impaired controllability in networks supporting cognitive and emotional control.

•

Weaker connectivity as well as topological alterations contribute to these changes.