Longitudinal studies of bipolar patients and their families: translating findings to advance individualized risk prediction, treatment and research

BACKGROUND

Bipolar disorder is a broad diagnostic construct associated with significant phenotypic and genetic heterogeneity challenging progress in clinical practice and discovery research. Prospective studies of well-characterized patients and their family members have identified lithium responsive (LiR) and lithium non-responsive (LiNR) subtypes that hold promise for advancement.

METHOD

In this narrative review, relevant observations from published longitudinal studies of well-characterized bipolar patients and their families spanning six decades are highlighted. DSM diagnoses based on SADS-L interviews were decided in blind consensus reviews by expert clinicians. Genetic, neurobiological, and psychosocial factors were investigated in subsets of well-characterized probands and adult relatives. Systematic maintenance trials of lithium, antipsychotics, and lamotrigine were carried out. Clinical profiles that included detailed histories of the clinical course, symptom sets and disorders segregating in families were documented. Offspring of LiR and LiNR families were repeatedly assessed up to 20 years using KSADS-PL format interviews and DSM diagnoses and sub-threshold symptoms were decided by expert clinicians in blind consensus reviews using all available clinical and research data.

RESULTS

A characteristic clinical profile differentiated bipolar patients who responded to lithium stabilization from those who did not. The LiR subtype was characterized by a recurrent fully remitting course predominated by depressive episodes and a positive family history of episodic remitting mood disorders, and not schizophrenia. Response to lithium clustered in families and the characteristic clinical profile predicted lithium response, with the episodic remitting course being a strong correlate. There is accumulating evidence that genetic and neurobiological markers differ between LiR and LiNR subtypes. Further, offspring of bipolar parents subdivided by lithium response differed in developmental history, clinical antecedents and early course of mood disorders. Moreover, the nature of the emergent course bred true from parent to offspring, independent of the nature of emergent psychopathology.

CONCLUSIONS

Bipolar disorders are heterogeneous and response to long-term lithium is associated with a familial subtype with characteristic course, treatment response, family history and likely pathogenesis. Incorporating distinctive clinical profiles that index valid bipolar subtypes into routine practice and research will improve patient outcomes and advance the development and translation of novel treatment targets to improve prevention and early intervention.

Predicting the risk and timing of major mood disorder in offspring of bipolar parents: exploring the utility of a neural network approach

Background

Bipolar disorder onset peaks over early adulthood and confirmed family history is a robust risk factor. However, penetrance within families varies and most children of bipolar parents will not develop the illness. Individualized risk prediction would be helpful for identifying those young people most at risk and to inform targeted intervention. Using prospectively collected data from the Canadian Flourish High-risk Offspring cohort study available in routine practice, we explored the use of a neural network, known as the Partial Logistic Artificial Neural Network (PLANN) to predict the time to diagnosis of major mood disorders in 1, 3 and 5-year intervals.

Results

Overall, for predictive performance, PLANN outperformed the more traditional discrete survival model for 3-year and 5-year predictions. PLANN was better able to discriminate or rank individuals based on their risk of developing a major mood disorder, better able to predict the probability of developing a major mood disorder and better able to identify individuals who would be diagnosed in future time intervals. The average AUC achieved by PLANN for 5-year prediction was 0.74, which indicates good discrimination.

Conclusions

This evaluation of PLANN is a useful step in the investigation of using neural networks as tools in the prediction of mood disorders in at-risk individuals and the potential that neural networks have in this field. Future research is needed to replicate these findings in a separate high-risk offspring sample.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40345-021-00228-2.

Improved Parent-Child Interactions Predict Reduced Internalizing Symptoms Among the Offspring of Parents with Bipolar Disorder Undergoing a Prevention Program: A Proof-of-Concept Study

The offspring of parents with bipolar disorder (OBD) exhibit elevated rates of psychopathology. However, preventative interventions are lacking. Using a quasi-experimental design with an assessment-only control group, we examined if a 12-week program (entitled Reducing Unwanted Stress in the Home, RUSH) decreases internalizing and externalizing symptoms in the OBD (aged 6-11 years) via intervention-related gains in parent-child interaction quality. Participants consisted of 55 offspring (26 OBD; 29 controls) and their parents. Assessments were conducted at four time points up to six months following the end of the RUSH program, during which parent and teacher ratings of child symptoms, and parent-child interaction quality (parental positivity and negativity, and dyadic mutuality) were measured. Multilevel modelling showed improved parental positivity and negativity, and dyadic mutuality among target dyads immediately and six months post-intervention. For the bootstrapping mediation analyses, intervention-related change in parental negativity fully mediated the relations between having participated in the RUSH program and lower parent-reported internalizing problems among the OBD six months later. These data provide evidence of the efficacy of the RUSH program for OBD who exhibited improved interactions with their parents post-intervention. Further investigation via a randomized controlled trial is warranted.

Adversity and Depression: The Moderating Role of Stress Reactivity among High and Low Risk Youth

Adverse life events have been causally linked to depression among youth at high risk for depression. But given that not all high-risk youth develop depression following adversity, individual differences in various processes, including physiological reactivity to stress, are likely to be at play. This longitudinal prospective study tested the hypothesis that, among high-risk youth exposed to adversities, extent of physiological reactivity to laboratory stress (indexed as respiratory sinus arrhythmia; RSA) would predict subsequent depressive symptoms. Subjects were youth at high (n = 80) and low (n = 74) familial risk for depression. At Time 1 (T1), RSA was assessed during a cognitive stress task. At Time 2 (T2) about 2 years later, parents reported on adversities experienced by their offspring during the interim. At T1 and T2, youth received a diagnostic evaluation, which included assessment of their depressive symptoms. The three-way interaction of group-X-adversities-X-RSA predicted T2 depressive symptoms (controlling for T1 depressive symptoms). This interaction was mostly driven by the moderating effect of RSA among high-risk youth, such that adversities predicted higher depressive symptoms for those who displayed greater RSA reactivity to stress. Among low-risk youth, an inverse marginal moderating effect of RSA was found, such that adversities tended to predict depressive symptoms for those who displayed blunted RSA reactivity to stress. Thus, high physiological stress reactivity appears to be an additional risk factor for depressive symptoms only among youth at elevated risk for such outcomes, and should be taken into consideration in efforts to prevent depression in these populations.

Affective lability in offspring of parents with major depressive disorder, bipolar disorder and schizophrenia

Affective lability, defined as the propensity to experience excessive and unpredictable changes in mood, has been proposed as a potential transdiagnostic predictor of major mood and psychotic disorders. A parental diagnosis of bipolar disorder has been associated with increased affective lability in offspring. However, the association between affective lability and family history of other mood and psychotic disorders has not been examined. We measured affective lability using the self- and parent-reported Children's Affective Lability Scale in a cohort of 320 youth aged 6-17 years, including 137 offspring of a parent with major depressive disorder, 68 offspring of a parent with bipolar disorder, 24 offspring of a parent with schizophrenia, and 91 offspring of control parents. We tested differences in affective lability between groups using mixed-effects linear regression. Offspring of a parent with major depressive disorder (β = 0.46, 95% CI 0.17-0.76, p = 0.002) or bipolar disorder (β = 0.47, 95% CI 0.12-0.81, p = 0.008) had significantly higher affective lability scores than control offspring. Affective lability did not differ significantly between offspring of a parent with schizophrenia and offspring of control parents. Our results suggest that elevated affective lability during childhood is a marker of familial risk for mood disorders.

Epigenetic markers in inflammation-related genes associated with mood disorder: a cross-sectional and longitudinal study in high-risk offspring of bipolar parents

Bipolar disorder is highly heritable and typically onsets in late adolescence or early adulthood. Evidence suggests that immune activation may be a mediating pathway between genetic predisposition and onset of mood disorders. Building on a prior study of mRNA and protein levels in high-risk offspring published in this Journal, we conducted a preliminary examination of methylation profiles in candidate immune genes from a subsample of well-characterized emergent adult (mean 20 years) offspring of bipolar parents from the Canadian Flourish high-risk cohort. Models were adjusted for variable age at DNA collection, sex and antidepressant and mood stabilizer use. On cross-sectional analysis, there was evidence of higher methylation rates for BDNF-1 in high-risk offspring affected (n = 27) and unaffected (n = 23) for mood disorder compared to controls (n = 24) and higher methylation rates in affected high-risk offspring for NR3C1 compared to controls. Longitudinal analyses (25 to 34 months) provided evidence of steeper decline in methylation rates in controls (n = 24) for NR3C1 compared to affected (n = 15) and unaffected (n = 11) high-risk offspring and for BDNF-2 compared to affected high-risk. There was insufficient evidence that changes in any of the candidate gene methylation rates were associated with illness recurrence in high-risk offspring. While preliminary, findings suggest that longitudinal investigation of epigenetic markers in well-characterized high-risk individuals over the peak period of risk may be informative to understand the emergence of bipolar disorder.

Resting-state fMRI signals in offspring of parents with bipolar disorder at the high-risk and ultra-high-risk stages and their relations with cognitive function

BACKGROUND

Bipolar disorder (BD) has been associated with dysfunctional resting-state brain functioning. However, it is still not known whether the aberrant functioning occurs and predict cognitive functioning before illness onset.

AIMS

We examined the resting-state regional and network dysfunctioning, and their correlates with neurocognitive performance, in the high-risk (HR) and ultra-high-risk (UHR) stages of bipolar disorder.

METHODS

Using amplitude of low-frequency fluctuations (ALFF), region homogeneity (ReHo) and hypothesis-driven region-of-interest (ROI)-based connectivity, we examined resting-state fMRI data of 8- to 25-year-old healthy offspring (HR, n = 28) and offspring with subthreshold syndromes (UHR, n = 22) of a BD parent, and age-matched healthy controls without any personal or family psychopathology (HC, n = 46). Participants' neurocognitive profiles were assessed using the MATRICS Consensus Cognitive Battery (MCCB).

RESULTS

ALFF signals in the left putamen and right rolandic operculum were lower in the HR group compared to the HC group. In contrast, ALFF signals were increased in the UHR group in the right middle pars orbitalis of the inferior frontal gyrus, right calcarine sulcus and right cerebellum. Connectivities between the right amygdala and left inferior temporal gyrus, between the left hippocampus and inferior occipital gyrus, and between the left hippocampus and middle pars orbitalis gyrus were decreased in the HR group compared to the HC group. In UHR versus HC group, connectivity between the right amygdala and the left hippocampus and left insula was increased, and connectivity between the left hippocampus and the left insula and the cerebellum was also increased. Among cognitive measures, processing speed was positively correlated with ALFF signals in the left putamen in the HR offspring. In the UHR offspring, processing speed, attention, and verbal learning/memory were positively correlated with the functional connectivity between the left hippocampus and cerebellum.

CONCLUSIONS

Offspring of parents with BD in the HR and UHR stages show largely non-overlapping patterns of atypical resting-state signals and functional connectivity that predicted cognitive functioning, possibly reflecting inherited abnormalities and/or complimentary reactions.

Gray matter volumes in symptomatic and asymptomatic offspring of parents diagnosed with bipolar disorder

Children of parents diagnosed with bipolar disorder (BD), termed high-risk offspring (HRO), are at greater risk of developing psychiatric disorders compared to healthy children of healthy parents (HCO). Gray matter volume (GMV) abnormalities have been observed in HRO, however, these reports are inconsistent. We posit that this variability may be attributed to differences in methodology among offspring studies; in particular, the presence of psychiatric symptoms in HRO. Here, we directly compared GMVs between symptomatic and asymptomatic HRO, and HCO. High-resolution T1-weighted MR images were collected from 31 HRO (18 symptomatic and 13 asymptomatic) and 20 age- and sex-matched HCO. HRO had at least one parent diagnosed with BD. Symptomatic HRO were defined as having a psychiatric diagnosis other than BD, while asymptomatic HRO were required to be free of any psychiatric diagnosis. Scans were processed using voxel-based morphometry methods and between group analyses were performed in SPM. Compared to HCO, the HRO group showed decreased GMV in the right inferior orbitofrontal, right middle frontal, and bilateral superior and middle temporal regions. Both symptomatic and asymptomatic HRO groups showed decreased GMV in these regions separately when compared to HCO. When comparing symptomatic and asymptomatic HRO, GMVs were comparable in all regions except the lateral occipital cortex. Our study compared symptomatic and asymptomatic HRO directly. In doing so, we provided further support for the presence of discrete GMV deficits in HRO, and confirmed that these deficits are present irrespective of the presence of symptoms in HRO.

Repeated salivary daytime cortisol and onset of mood episodes in offspring of bipolar parents

Background

Differences in cortisol secretion may differentiate individuals at high compared to low genetic risk for bipolar disorder (BD) and predict the onset or recurrence of mood episodes. The objectives of this study were to determine if salivary cortisol measures are: (1) different in high-risk offspring of parents with BD (HR) compared to control offspring of unaffected parents (C), (2) stable over time, (3) associated with the development of mood episode onset/recurrence, and (4) influenced by comorbid complications.

Methods

Fifty-three HR and 22 C completed salivary cortisol sampling annually for up to 4 years in conjunction with semi-structured clinical interviews. The cortisol awakening response (CAR), daytime cortisol [area under the curve (AUC)], and evening cortisol (8:00 p.m.) were calculated.

Results

There were no differences in baseline CAR, AUC and evening cortisol between HR and C (p = 0.38, p = 0.30 and p = 0.84), respectively. CAR, AUC and evening cortisol were stable over yearly assessments in HR, while in Cs, evening cortisol increased over time (p = 0.008), and CAR and AUC remained stable. In HR, AUC and evening cortisol increased the hazard of a new onset mood disorder/recurrence by 2.7 times (p = 0.01), and 3.5 times (p = 0.01), respectively, but this was no longer significant after accounting for multiple comparisons.

Conclusions

Salivary cortisol is stable over time within HR offspring. However, between individuals, basal salivary cortisol is highly variable. More research is needed, with larger samples of prospectively studied HR youth using a more reliable method of cortisol measurement, to determine the potential role of cortisol in the development of mood disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s40345-016-0053-5) contains supplementary material, which is available to authorized users.

Accuracy of emotion labeling in children of parents diagnosed with bipolar disorder

BACKGROUND

Emotion labeling deficits have been posited as an endophenotype for bipolar disorder (BD) as they have been observed in both patients and their first-degree relatives. It remains unclear whether these deficits exist secondary to the development of psychiatric symptoms or whether they can be attributed to risk for psychopathology. To explore this, we investigated emotion processing in symptomatic and asymptomatic high-risk bipolar offspring (HRO) and healthy children of healthy parents (HCO).

METHODS

Symptomatic (n:18, age: 13.8 ± 2.6 years, 44% female) and asymptomatic (n:12, age: 12.8 ± 3.0 years, 42% female) HRO and age- and sex-matched HCO (n:20, age: 13.3 ± 2.5 years, 45% female) performed an emotion-labeling task. Total number of errors, emotion category and intensity of emotion error scores were compared. Correlations between total error scores and symptom severity were also investigated.

RESULTS

Compared to HCO, both HRO groups made more errors on the adult face task (pcor=0.014). The HRO group were 2.3 times [90%CI:0.9-6.3] more likely and 4.3 times [90%CI:1.3-14.3] more likely to make errors on sad and angry faces, respectively. With the exception of sad face type errors, we observed no significant differences in error patterns between symptomatic and asymptomatic HRO, and no correlations between symptom severity and total number of errors.

LIMITATIONS

This study was cross-sectional in design, limiting our ability to infer trajectories or heritability of these deficits.

CONCLUSIONS

This study provides further support for emotion labeling deficits as a candidate endophenotype for BD. Our study also suggests these deficits are not attributable to the presence of psychiatric symptoms.

Childhood anxiety: an early predictor of mood disorders in offspring of bipolar parents

BACKGROUND

Anxiety disorders are common among the offspring of parents with bipolar disorder (BD). This study investigated the nature of the association between anxiety disorders and mood disorders in a prospectively studied high-risk cohort.

METHODS

High-risk offspring were identified from families in which one parent had confirmed BD based on SADS-L interviews and best estimate diagnostic procedures. All agreeable offspring aged 8-25 years were enrolled in a longitudinal study involving repeated KSADS-PL format clinical assessments. Control (C) offspring from families in which neither parent met lifetime criteria for a psychiatric disorder were similarly assessed. All DSM-IV diagnoses in the offspring were confirmed on blind consensus review. Cumulative incidence and adjusted Cox Proportional Hazards models were used to calculate the risk of anxiety disorders and the predictive association with mood disorders.

RESULTS

The cumulative incidence of anxiety disorders was higher (23.40% vs. 10.42%; HR=2.136; p=.0382) and occurred earlier (9.79 vs. 14.84 years; p=.0125) in high-risk compared to C offspring. In high-risk offspring generalized anxiety disorders (GAD) followed by social phobia were the most incident anxiety subtypes; while high emotionality (HR 1.111; p=.0096) and shyness (HR 1.144; p=.0053) increased the risk of anxiety disorders. Anxiety disorders increased the adjusted risk of mood disorders (HR 2.166; p=.0004), on average 8.49 years later (SD 5.97).

LIMITATIONS

The cumulative incidence of BD is relatively low, as the cohort is still in the period of risk.

CONCLUSIONS

Findings highlight the need for longitudinal surveillance of symptomatic high-risk children and suggest anxiety disorders are an important early intervention target.