Unipolar relatives in bipolar pedigrees: a search for elusive indicators of underlying bipolarity

Development and validation of a risk calculator for major mood disorders among the offspring of bipolar parents using information collected in routine clinical practice

BACKGROUND

Family history is a significant risk factor for bipolar disorders (BD), but the magnitude of risk varies considerably between individuals within and across families. Accurate risk estimation may increase motivation to reduce modifiable risk exposures and identify individuals appropriate for monitoring over the peak risk period. Our objective was to develop and independently replicate an individual risk calculator for bipolar spectrum disorders among the offspring of BD parents using data collected in routine clinical practice.

METHODS

Data from the longitudinal Canadian High-Risk Offspring cohort study collected from 1996 to 2020 informed the development of a 5 and 10-year risk calculator using parametric time-to-event models with a cure fraction and a generalized gamma distribution. The calculator was then externally validated using data from the Lausanne-Geneva High-Risk Offspring cohort study collected from 1996 to 2020. A time-varying C-index by age in years was used to estimate the probability that the model correctly classified risk. Bias corrected estimates and 95% confidence limits were derived using a jackknife resampling approach.

FINDINGS

The primary outcome was age of onset of a major mood disorder. The risk calculator was most accurate at classifying risk in mid to late adolescence in the Canadian cohort (n = 285), and a similar pattern was replicated in the Swiss cohort (n = 128). Specifically, the time-varying C-index indicated that there was approximately a 70% chance that the model would correctly predict which of two 15-year-olds would be more likely to develop the outcome in the future. External validation within a smaller Swiss cohort showed mixed results.

INTERPRETATION

Findings suggest that this model may be a useful clinical tool in routine practice for improved individualized risk estimation of bipolar spectrum disorders among the adolescent offspring of a BD parent; however, risk estimation in younger high-risk offspring is less accurate, perhaps reflecting the evolving nature of psychopathology in early childhood. Based on external validation with a Swiss cohort, the risk calculator may not be as predictive in more heterogenous high-risk populations.

FUNDING

The Canadian High-Risk Study has been funded by consecutive operating grants from the Canadian Institutes for Health Research, currently CIHR PJT Grant 152796 he Lausanne-Geneva high-risk study was and is supported by five grants from the Swiss National Foundation (#3200-040,677, #32003B-105,969, #32003B-118,326, #3200-049,746 and #3200-061,974), three grants from the Swiss National Foundation for the National Centres of Competence in Research project "The Synaptic Bases of Mental Diseases" (#125,759, #158,776, and #51NF40 - 185,897), and a grant from GlaxoSmithKline Clinical Genetics.

Daily and weekly mood ratings using a remote capture method in high-risk offspring of bipolar parents: Compliance and symptom monitoring

OBJECTIVES

To determine the compliance and clinical utility of weekly and daily electronic mood symptom monitoring in adolescents and young adults at risk for mood disorder.

METHODS

Fifty emerging adult offspring of bipolar parents were recruited from the Flourish Canadian high-risk offspring cohort study along with 108 university student controls. Participants were assessed by KSADS/SADS-L semi-structured interviews and used a remote capture method to complete weekly and daily mood symptom ratings using validated scales for 90 consecutive days. Hazard models and generalized estimating equations were used to determine differences in summary scores and regularity of ratings.

RESULTS

Seventy-eight and 77% of high-risk offspring and 97% and 93% of controls completed the first 30 days of weekly and daily ratings, respectively. There were no differences in drop-out rates between groups over 90 days (weekly P = 0.2149; daily P = 0.9792). There were no differences in mean summary scores or regularity of weekly anxiety, depressive or hypomanic symptom ratings between high-risk offspring and control groups. However, high-risk offspring compared to controls had daily ratings indicating lower positive affect, higher negative affect and lower self-esteem (P = 0.0317). High-risk offspring with remitted mood disorder compared to those without had more irregularity in weekly anxiety and depressive symptom ratings and daily ratings of lower positive affect, higher negative affect, and higher shame and self-doubt (P = 0.0365).

CONCLUSIONS

Findings support that high-resolution electronic mood tracking may be a feasible and clinically useful approach in monitoring emerging psychopathology in young people at high-risk offspring of mood disorder onset or recurrence.

Patterns and predictors of conversion to bipolar disorder in 91 587 individuals diagnosed with unipolar depression

OBJECTIVE

Conversion from unipolar depression (UD) to bipolar disorder (BD) is a clinically important event that should lead to treatment modifications. Unfortunately, recognition of this transition is often delayed. Therefore, the objective of this study was to identify predictors of diagnostic conversion from UD to BD.

METHOD

Historical prospective cohort study based on 91 587 individuals diagnosed with UD in Danish hospital psychiatry between 1995 and 2016. The association between a series of potential predictors and the conversion from UD to BD during follow-up (702 710 person-years) was estimated by means of Cox regression with death as competing risk.

RESULTS

During follow-up, 3910 individuals with UD developed BD. The cumulative incidence of conversion was slightly higher in females (8.7%, 95% CI: 8.2-9.3) compared to males (7.7%, 95% CI: 7.0-8.4). The strongest predictor of conversion from UD to BD was parental history of BD (adjusted hazard ratio (aHR) = 2.60, 95% CI: 2.20-3.07)). Other predictors included psychotic depression at the index UD episode (aHR = 1.73, 95% CI: 1.48-2.02), a prior/concomitant non-affective psychosis (aHR = 1.73, 95% CI: 1.51-1.99), and in-patient treatment at the index episode (aHR = 1.76, 95% CI: 1.63-1.91).

CONCLUSION

Diagnostic conversion from UD to BD is predicted by severe depression requiring in-patient treatment, psychotic symptomatology, and parental history of BD.

Risk factors for conversion from unipolar psychotic depression to bipolar disorder

OBJECTIVES

Patients with unipolar psychotic depression (PD) are at high risk of developing bipolar disorder (BD). This conversion has important implications for the choice of treatment. This study, therefore, aimed to identify risk factors associated with diagnostic conversion from PD to BD.

METHODS

We conducted a population-based, historical prospective cohort study by merging data from Danish registers. Patients assigned an ICD-10 diagnosis of PD between 1 January 1995 and 31 December 2007 were identified in the Danish Central Psychiatric Research Register and were followed until the development of BD, death, loss to follow-up, or 31 December 2007. Potential risk factors for conversion to BD, also defined through various Danish registers, were tested in multiple logistic regression analyses with risk expressed as adjusted odds ratios (AOR).

RESULTS

We identified 8,588 patients with PD, of whom 609 (7.1%) developed BD during follow-up. The following characteristics were significantly associated with diagnostic conversion from PD to BD: early onset of PD [AOR = 0.99 (per year of increasing age), p = 0.044], recurrent depression [AOR = 1.02 (per episode), p = 0.036], living alone (AOR = 1.29, p = 0.007), receiving a disability pension (AOR = 1.55, p < 0.001), and the highest educational level being a technical education (AOR = 1.55, p < 0.001), short-cycle higher education (AOR = 2.65, p < 0.001), or medium-cycle higher education (AOR = 1.75, p < 0.001).

CONCLUSIONS

Diagnostic conversion to BD was prevalent among patients with PD. The following characteristics were significantly associated with this conversion: early onset of PD, recurrent depression, living alone, receiving a disability pension, and the highest educational level being a technical education, short-cycle higher education, or medium-cycle higher education.

Challenges in the treatment of major depressive disorder with psychotic features

Psychotic depression is associated with significant morbidity and mortality but is underdiagnosed and undertreated. In recent years, there have been several studies that have increased our knowledge regarding the optimal treatment of patients with psychotic depression. The combination of an antidepressant and antipsychotic is significantly more effective than either antidepressant monotherapy or antipsychotic monotherapy for the acute treatment of psychotic depression. Most treatment guidelines recommend either the combination of an antidepressant with an antipsychotic or ECT for the treatment of an acute episode of unipolar psychotic depression. The optimal maintenance treatment after a person responds to either the antidepressant/antipsychotic combination or the ECT is unclear particularly as it pertains to length of time the patient needs to take the antipsychotic medication. Little is known regarding the optimal treatment of a patient with bipolar disorder who has an episode of psychotic depression or the clinical characteristics of responders to medication treatments vs ECT treatments.

Environmental and familial risk factors for psychotic and non-psychotic severe depression

BACKGROUND

Severe unipolar depression can be classified as either psychotic depression (PD) or non-psychotic depression (non-PD). A number of biological and clinical differences have been detected between PD and non-PD, but it remains unknown whether risk factors for the two subtypes also differ. The aim of the present study was therefore to investigate whether a number of potential risk factors influenced the risk of developing PD and non-PD to different extents.

METHODS

This is a register-based historical prospective cohort study following all 2.4 million individuals born in Denmark between 1955 and 1990. During follow-up 2183 and 9101 individuals were registered in the Danish Psychiatric Central Research Register with PD and non-PD respectively. The association between risk factors and the development of PD and non-PD was estimated by survival analysis (Poisson regression) and expressed as incidence rate ratios (IRR).

RESULTS

The most consistent finding of the study was that of a general overlap in familial and environmental risk factors for PD and non-PD. However, a parental history of bipolar disorder was a risk factor for PD (mother, IRR=1.66, p=0.003. Father, IRR=1.56, p=0.040) and not for non-PD (mother, IRR=0.92, p=0.430. Father, IRR=1.08, p=0.552). Conversely, a positive family history of schizophrenia was associated with neither PD nor non-PD LIMITATIONS: Diagnoses were assigned as part of routine clinical practice.

CONCLUSION

Our findings justify the distinction between PD and non-PD in the current diagnostic manuals. Furthermore, the fact that parental bipolar disorder and not schizophrenia was a risk factor for PD supports the Kraepelinian dichotomy.

Paternal age effect on age of onset in bipolar I disorder is mediated by sex and family history

This study investigated for the first time in the psychiatric literature the effect of parental age on age-of-onset (AO) in bipolar I disorder (BPI) in relation to proband sex and family history (FH) for major psychoses in a sample of 564 BPI probands. All probands, 72.68% of their first-degree and 12.13% of their second-degree relatives were directly interviewed. The FH-method was used for all unavailable relatives. The diagnoses were made according to DSM-IV(TR) . The impact of parental age on proband early/late AO was evaluated through logistic regression with the cut-off for early AO determined through commingling analysis. We found evidence for a significant influence of increasing paternal age, and especially age ≥ 35 years, on AO of BPI disorder in the total sample (OR = 0.54, CI: 0.35-0.80), in the female subsample (OR = 0.44, CI: 0.25-0.78), in the sporadic subsample (OR = 0.64, CI: 0.38-0.95), and in the subsample with FH of recurrent unipolar major depression (Mdd-RUP) (OR = 0.55, CI: 0.34-0.87). No significant effect of paternal age on disease AO was found in patients with FH of bipolar (BP), schizoaffective disorders (SA), or schizophrenia (SCZ), nor in males. Mean age was significantly higher in fathers of sporadic cases and of cases with FH of Mdd-RUP than in fathers of cases with FH of BP/SA/SCZ (P = 0.011). Maternal age had no significant effect either in the total sample or in subsamples defined by proband sex or FH. In conclusion, in our sample increasing paternal age lowered the onset of BPI selectively, the effect being related to the female sex and FH-type.

Comparison of depressive episodes in bipolar disorder and in major depressive disorder within bipolar disorder pedigrees

BACKGROUND

Although genetic epidemiological studies have confirmed increased rates of major depressive disorder among the relatives of people with bipolar affective disorder, no report has compared the clinical characteristics of depression between these two groups.

AIMS

To compare clinical features of depressive episodes across participants with major depressive disorder and bipolar disorder from within bipolar disorder pedigrees, and assess the utility of a recently proposed probabilistic approach to distinguishing bipolar from unipolar depression. A secondary aim was to identify subgroups within the relatives with major depression potentially indicative of 'genetic' and 'sporadic' subgroups.

METHOD

Patients with bipolar disorder types 1 and 2 (n = 246) and patients with major depressive disorder from bipolar pedigrees (n = 120) were assessed using the Diagnostic Interview for Genetic Studies. Logistic regression was used to identify distinguishing clinical features and assess the utility of the probabilistic approach. Hierarchical cluster analysis was used to identify subgroups within the major depressive disorder sample.

RESULTS

Bipolar depression was characterised by significantly higher rates of psychomotor retardation, difficulty thinking, early morning awakening, morning worsening and psychotic features. Depending on the threshold employed, the probabilistic approach yielded a positive predictive value ranging from 74% to 82%. Two clusters within the major depressive disorder sample were found, one of which demonstrated features characteristic of bipolar depression, suggesting a possible 'genetic' subgroup.

CONCLUSIONS

A number of previously identified clinical differences between unipolar and bipolar depression were confirmed among participants from within bipolar disorder pedigrees. Preliminary validation of the probabilistic approach in differentiating between unipolar and bipolar depression is consistent with dimensional distinctions between the two disorders and offers clinical utility in identifying patients who may warrant further assessment for bipolarity. The major depressive disorder clusters potentially reflect genetic and sporadic subgroups which, if replicated independently, might enable an improved phenotypic definition of underlying bipolarity in genetic analyses.

Family, twin, and adoption studies of bipolar disorder

Family, twin, and adoption studies have been essential in defining the genetic epidemiology of bipolar disorder over the past several decades. Family studies have documented that first-degree relatives of affected individuals have an excess risk of the disorder, while twin studies (and to a lesser extent, adoption studies) suggest that genes are largely responsible for this familial aggregation. We review these studies, including the magnitude of familial risk and heritability estimates, efforts to identify familial subtypes of bipolar disorder, and the implications of family/genetic data for validating nosologic boundaries. Taken together, these studies indicate that bipolar disorder is phenotypically and genetically complex.

Genetic linkage and association studies in bipolar affective disorder: a time for optimism

Genetic research on complex diseases is beginning to bear fruit, with the successful identification of candidate susceptibility genes in diabetes, asthma, and other illnesses. Similar success is on the horizon for bipolar affective disorder (BPAD), but significant challenges remain. In this review, we outline the basic concepts of linkage and association mapping for complex phenotypes. We point out important caveats inherent in both approaches, and review guidelines on the interpretation of linkage statistics and significance thresholds. We then apply these concepts to an evaluation of the present status of genetic linkage and association studies in BPAD. The challenges posed by locus heterogeneity, phenotype definition, and sample size requirements are given a detailed treatment. Despite these challenges, we argue that the way ahead remains firmly rooted in linkage studies, complemented by association studies in linked regions. This is the only truly genome-wide approach currently available; it has succeeded in other complex phenotypes, and it is the surest strategy for mapping susceptibility genes in BPAD. Once these genes are identified, genetic mapping methods will yield to the other methods of 21st-century molecular biology as we begin to elucidate the pathophysiology of BPAD.

JI, Craddock N, DePaulo JR, Baron M, Gershon ES, Ekholm J, Cichon S, Turecki G, Claes S, Kelsoe JR, Schofield PR, Badenhop RF, Morissette J, Coon H, Blackwood D, McInnes LA, Foroud T, Edenberg HJ, Reich T, Rice JP, Goate A, McInnis MG, McMahon FJ, Badner JA, Goldin LR, Bennett P, Willour VL, Zandi PP, Liu J, Gilliam C, Juo SH, Berrettini WH, Yoshikawa T, Peltonen L, Lönnqvist J, Nöthen MM, Schumacher J, Windemuth C, Rietschel M, Propping P, Maier W, Alda M, Grof P, Rouleau GA, Del-Favero J, Van Broeckhoven C, Mendlewicz J, Adolfsson R, Spence MA, Luebbert H, Adams LJ, Donald JA, Mitchell PB, Barden N, Shink E, Byerley W, Muir W, Visscher PM, Macgregor S, Gurling H, Kalsi G, McQuillin A, Escamilla MA, Reus VI, Leon P, Freimer NB, Ewald H, Kruse TA, Mors O, Radhakrishna U, Blouin JL, Antonarakis SE, Akarsu N. Genome scan meta-analysis of schizophrenia and bipolar disorder, part III: Bipolar disorder

Genome scans of bipolar disorder (BPD) have not produced consistent evidence for linkage. The rank-based genome scan meta-analysis (GSMA) method was applied to 18 BPD genome scan data sets in an effort to identify regions with significant support for linkage in the combined data. The two primary analyses considered available linkage data for "very narrow" (i.e., BP-I and schizoaffective disorder-BP) and "narrow" (i.e., adding BP-II disorder) disease models, with the ranks weighted for sample size. A "broad" model (i.e., adding recurrent major depression) and unweighted analyses were also performed. No region achieved genomewide statistical significance by several simulation-based criteria. The most significant P values (<.01) were observed on chromosomes 9p22.3-21.1 (very narrow), 10q11.21-22.1 (very narrow), and 14q24.1-32.12 (narrow). Nominally significant P values were observed in adjacent bins on chromosomes 9p and 18p-q, across all three disease models on chromosomes 14q and 18p-q, and across two models on chromosome 8q. Relatively few BPD pedigrees have been studied under narrow disease models relative to the schizophrenia GSMA data set, which produced more significant results. There was no overlap of the highest-ranked regions for the two disorders. The present results for the very narrow model are promising but suggest that more and larger data sets are needed. Alternatively, linkage might be detected in certain populations or subsets of pedigrees. The narrow and broad data sets had considerable power, according to simulation studies, but did not produce more highly significant evidence for linkage. We note that meta-analysis can sometimes provide support for linkage but cannot disprove linkage in any candidate region.

The prevalence of migraine in patients with bipolar and unipolar affective disorders

There is a well-known association between migraine and affective disorders, but the information is sparse concerning the prevalence of migraine in subgroups of the affective disorders. The present study was undertaken to investigate the prevalence of migraine in unipolar depressive, bipolar I and bipolar II disorders. Patients with major affective disorders (n = 62), consecutively admitted to an open psychiatric ward, were examined with a semi-structured interview based on DSM-IV diagnostic criteria, combined with separate criteria for affective temperaments. Diagnosis of unipolar and bipolar I disorders followed the DSM-IV criteria, while bipolar II disorder encompassed patients with either discrete hypomanic episodes or a cyclothymic temperament. Migraine was diagnosed according to IHS-criteria. Symptoms of migraine were found to be common in these patients, both in those with unipolar depression (46% prevalence of migraine) and in those with bipolar disorders (44% prevalence). Among the bipolar patients there was, however, a striking difference between the two diagnostic subgroups, with a prevalence of 77% in the bipolar II group compared with 14% in the bipolar I group (P = 0.001). These results support the contention that bipolar I and II are biologically separate disorders and point to the possibility of using the association of bipolar II disorder with migraine to study both the pathophysiology and the genetics of this affective disorder.

Bipolar versus unipolar psychotic outpatient depression

BACKGROUND

The relationship between bipolar and unipolar psychotic depression has not been well studied. Therefore, the aim of the present study was to compare bipolar with unipolar psychotic outpatient depression.

METHODS

Seventy consecutive unipolar (n = 40) and bipolar (n = 30) psychotic depressed outpatients were interviewed with the Structured Clinical Interview for DSM-IV, the Montgomery Asberg Depression Rating Scale, the Global Assessment of Functioning Scale, and the Brief Psychiatric Rating Scale.

RESULTS

Of the variables studied (age, duration of illness, severity, recurrences, atypical features, chronicity, gender, comorbidity, hallucinations, delusions), none was significantly different between unipolar and bipolar psychotic patients.

CONCLUSIONS

Bipolar psychotic depression was similar to unipolar psychotic depression on variables reported in the literature to distinguish bipolar from unipolar disorder.

CLINICAL IMPLICATIONS

The findings might suggest, but do not necessarily imply, that psychotic depression might be a distinct clinical entity.

LIMITATIONS

Single interviewer, nonblind cross-sectional assessment, outpatient sample, sample size.

Mode of inheritance in mood disorder families according to fluvoxamine response

Mood disorders are known to cluster within families, but the mode of transmission remains largely unknown. The purpose of our analysis was to determine whether selection of a sample that was homogeneous in its response to an antidepressant provided stronger evidence for a single major locus. Complex segregation analysis was applied to a sample of 171 Italian families of bipolar and unipolar probands that were responsive to the antidepressant fluvoxamine. We used regressive logistic analyses to determine the best fit from among environmental, arbitrary Mendelian, dominant, recessive and additive models. For the 171 affective families with probands that were responsive to the antidepressant fluvoxamine, a Mendelian model of inheritance was rejected. When considering 68 families of bipolar probands, the best fit was obtained for a Mendelian dominant model of transmission. The identification of a Mendelian mode of transmission in bipolar subjects who were selected according to their response to fluvoxamine supports the use of a pharmacological criterion as a tool for identifying true genetic disorders.