Association between circadian genes, bipolar disorders and chronotypes.

Abnormalities in circadian rhythms play an important role in the pathogenesis of bipolar disorders (BD). Previous genetic studies have reported discrepant results regarding associations between circadian genes and susceptibility to BD. Furthermore, plausible behavioral consequences of at-risk variants remain unclear since there is a paucity of correlates with phenotypic biomarkers such as chronotypes. Here, we combined association studies with a genotype/phenotype correlation in order to determine which circadian genes variants may be associated with the circadian phenotypes observed in patients with BD. First, we compared the allele frequencies of 353 single nucleotide polymorphisms spanning 21 circadian genes in two independent samples of patients with BD and controls. The meta-analysis combining both samples showed a significant association between rs774045 in TIMELESS (OR = 1.49 95%CI[1.18-1.88]; p = 0.0008) and rs782931 in RORA (OR = 1.31 95%CI[1.12-1.54]; p = 0.0006) and BD. Then we used a "reverse phenotyping approach" to look for association between these two polymorphisms and circadian phenotypes in a subsample of patients and controls. We found that rs774045 was associated with eveningness (p = 0.04) and languid circadian type (p = 0.01), whereas rs782931 was associated with rigid circadian type (p = 0.01). Altogether, these findings suggest that these variants in the TIMELESS and RORA genes may confer susceptibility to BD and impact on circadian phenotypes in carriers who thus had lower ability to properly adapt to external cues.

[Management of bipolar 1 disorder in children and adolescents]. / Prise en charge du trouble bipolaire de type 1 chez l'enfant et l'adolescent.

Lifetime prevalence of child and adolescent bipolar 1 disorder (BD1) is nearly 0.1 %. Even though it is not a frequent disorder in young people, there is an increased interest for this disorder at this age, because of the poor outcome, the severe functional impairments and the major risk of suicide. Diagnosis is complex in view of the more frequent comorbidities, the variability with an age-dependant clinical presentation, and the overlap in symptom presentation with other psychiatric disorders (e.g. disruptive disorders in prepubertal the child and schizophrenia in the adolescent). The presentation in adolescents is very similar to that in adults and in prepubertal children chronic persistent irritability and rapid mood oscillation are often at the foreground. For a while, such presentations were considered as BD-not otherwise specified (BD-NOS), which can explain the outburst of the prevalence of bipolar disorder in children in the US. Longitudinal studies that look for the outcome of such emotional dysregulations have not revealed an affiliation with bipolar disorder spectrum, but with depressive disorders in adulthood. The diagnosis of Disruptive Mood Dysregulation Disorder was proposed in the DSM-5 to identify these children and to prevent confusion with bipolar disorder. The goals of the pharmacological and psychosocial treatments are to control or ameliorate the symptoms, to avoid new episodes or recurrences, to improve psychosocial functioning and well-being, and to prevent suicide. In the US, lithium and four atypical antipsychotics have been approved by the FDA for 10 to 13-year-olds (risperidone, olanzapine, aripiprazole and quetiapine). In France, only lithium salts (after the age of 16) and aripiprazole (after the age of 13) are recommended. Psychosocial treatments, such as a familial or individual approach are developing.

Chronotypes of bipolar patients in remission: validation of the French version of the circadian type inventory in the FACE-BD sample.

Circadian rhythm disturbances have been associated with bipolar disorder (BD) during both the mood episodes and the periods of remission. Circadian phase preferences for the evening have been reported for remitted patients, whereas the amplitude and stability of their rhythms have never been assessed using questionnaires. The primary aim of our study was the validation of a French version of the Circadian Type Inventory (CTI), whereas its secondary aim was the comparison between remitted patients with BD and healthy controls for rhythm stability and amplitude and for phase preference. For this purpose, we used the CTI and the Composite Scale of Morningness (CSM) that assesses phase preference ("morning" or "evening" type). First, we report here on the validation of the French version of the 11-item Circadian Type Inventory in a sample of 140 remitted patients with BD and 156 healthy controls. Principal components analysis revealed a two-factor structure (FR: flexibility/rigidity scale corresponding to rhythm stability; LV: languid/vigorous scale corresponding to rhythm amplitude) explaining 52% of the variance in the control group and 47% in the bipolar group. Cronbach's alpha was 0.75 for FR and 0.73 for LV. The test-retest reliability was 0.74 for FR and 0.86 for LV (3 wks) and 0.62 for FR and 0.72 for LV (6 mos). LV and FR scores correlated with the Composite Scale of Morningness score (p < 0.00001 and p = 0.0002, respectively). Second, as compared with controls, patients with BD were more languid (p < 0.00001) and showed an evening preference (p = 0.0003), but they did not differ from the controls with regard to flexibility/rigidity. The French version of the CTI appeared to have satisfactory psychometrics characteristics. Bipolar patients exhibited not only abnormalities in phase preference but also in amplitude as measured by languidity. Since circadian rhythm dysfunction has been shown to predict poor functioning and mood relapses in interepisodic patients with BD, this tool would appear to be a promising, easy-to-use, measure of the amplitude and flexibility of circadian rhythms that could enrich the arsenal of assessments used in clinical settings.

Genetics of circadian rhythms and mood spectrum disorders.

Mood spectrum disorders (bipolar disorder, recurrent depressive disorder and seasonal affective disorder) are accompanied by circadian deregulations, which can occur during acute mood episodes as well as during euthymic periods, and are particularly common among bipolar patients in remission. This suggests that altered circadian rhythms may be biological markers of these disorders. Rhythm dysfunctions have been observed in mood disorder patients by using actigraphic measures and by assessing social metric rhythms, diurnal preferences and melatonin secretion. Since many of these markers are heritable and therefore driven by clock genes, these genes may represent susceptibility factors for mood spectrum disorders. Indeed, several genetic association studies have suggested that certain circadian gene variants play a role in susceptibility to these disorders. Such connections to circadian genes such as CLOCK, ARNTL1, NPAS2, PER3 and NR1D1 have been repeatedly demonstrated for bipolar disorders, and to a lesser extent for recurrent depressive disorders and seasonal affective disorders. The study of circadian phenotypes and circadian genes in mood spectrum disorders represents a major field of research that may yet reveal the pathophysiological determinants of these disorders.