INTRODUCTION: Emotional reactivity and sleep constitute key dimensions of bipolar disorder. Emotional reactivity referred to emotion response intensity and emotion response threshold. Higher emotion reactivity is described during both mood episodes and periods of remission in bipolar disorder. As well, sleep disturbances are described during both acute episodes and euthymic periods in bipolar disorder. Links between sleep and emotion regulation start to be studied in general population. Interactions between sleep and emotion systems can rely on shared neuronal structures, which involve limbic system. Future research on sleep and emotion regulation relationships is required in bipolar disorder.
METHODS: A systematic review of the scientific literature was conducted. Studies on emotional reactivity in bipolar disorder during periods of remission were presented. Sleep studies of bipolar disorder during inter-critical periods were discussed too. Researches on interactions between sleep and emotion regulation in general population were presented. Finally, therapeutic applications focusing on sleep and emotional regulation in bipolar disorder were described.
RESULTS: Patients with bipolar disorder display disturbances of sleep and emotion reactivity even during periods of remission. Indeed, bipolar patients display more intense and more labile emotions assessed by self-questionnaires, increase positive attribution to neutral stimuli corroborated by startle reflex, functional changing on imagery studies. Sleep disturbances during inter-critical periods refer to clinical poor sleep quality and to increase time in bed, more frequent nocturnal awaking, more variable sleep-wake patterns assessed by actigraphy and polysomnography. In general population some studies have shown the impact of sleep restriction on emotion dysregulation. F-MRI studies show that healthy participants present increase activation of some structures such as amygdala involved in emotion processing. Deregulation of these areas has already been noticed in previous studies of euthymic bipolar patients without sleep restriction procedure. Considering sleep and emotion processes enhance our understanding of medication action mechanisms. Lithium and sodium valproate reduce melatonin light sensitivity and increased the activity period. It can be postulated that these effects on circadian system can impact sleep regulation. Furthermore, an f-MRI study shows that mood stabilizers can reduce amygdala activation of bipolar patients compared to untreated bipolar patients during an emotional task. Emotion and sleep regulation can be targeted by specific psychotherapy. Interpersonal and social rhythm therapy, cognitive behavioral therapy of insomnia and mindfulness applied to bipolar disorder are presented and discussed.
DISCUSSION: Disturbances of sleep and emotional reactivity remain during periods of remission in bipolar disorder. Further research is required to better understand relationships between these two processes in bipolar disorder. Sleep and emotion dysgulations can be targeted by specific psychotherapy. More systematic assessment of sleep an emotional reactivity in remitted bipolar patients can lead to consider and treat this residual symptomatology that could reduce recurrences.
