Sleep patterns in bipolar disorder: systematic literature review

Abstract

Introduction Bipolar disorder (BD), also known as manic depression, is a chronic mood disorder defined by repetitive relapse of mood episodes between depression and mania. Sleep problems are commonly noted during the depressive episodes, manic episodes, and even euthymic episodes in patients with BD, as per the ICD -10 [1] a reduced need for sleep is a symptom of mania, whereas insomnia and hypersomnia are commonly noted in bipolar depression [2]. Aim To discuss common types of sleep disturbances, explore contributing factors, and evaluate their impact on the course of bipolar disorder. Methods A systematic literature review was performed according to PRISMA guidelines. The search with combination of keywords “bipolar disorder”, “sleep”, ‘’circadian rhythm” was performed up to November 11th, 2022, in PubMed, Google Scholar databases. Inclusion criteria: research articles published less than 10 years ago, full-text articles in the English language, prospective studies. Exclusion criteria: research articles are older than 10 year and were not written in English, clinical cases. Of the 1215 results, only those which specifically identified the associations between childhood sexual abuse and adult mental disorder. Selection criteria were applied, and 42 studies were selected for full-text analysis, 7 of them were included in this review. The titles and abstracts were analysed by the authors, followed by the selection of complete articles for reviewing and analysis according to the eligibility criteria. Results Sleep impairments are common in patients with BD, even in the euthymic state. However, the type of sleep disturbance depends on the prevailing mood state. Throughout the manic state, most patients encounter a reduced need for sleep (66–99%), while patients in the depressive state undergo insomnia (40–100%) and hypersomnia (23–78%) [2], [3]. It has been noted that irregularities in melatonin secretion are prevalent in BD patients [4]. Advanced melatonin peak time and increased secretion was recognized in patients in manic episodes, whereas patients in depressive episodes or euthymic states had delayed melatonin peak time and decreased secretion, suggesting that these dissimilarities are determined by predominant mood states [2], [5], [6]. It is notable that BD patients with impaired sleep patterns had considerably lower mood and worse psychosocial functioning opposed to patients with normal sleep [5], [7]. Bipolar disorder patients’ circadian rhythm dysfunctions interfere with the sleep–wake cycle and the secretion of serotonin and dopamine, hence, cause sleep difficulties and mood dysregulations [2]. Studies suggested that sleep disturbances were among the first prodromal signs of relapse of a mood episode, that aggravate during an episode [4], [6]. Conclusions In conclusion, bipolar disorder often co-occurs with sleep disturbances such as insomnia, hypersomnia, and reduced sleep time, which significantly affect patients' mood. Sleep and circadian rhythm abnormalities are prevalent throughout all stages of bipolar disorder and frequently signal the onset of a mood episode, emphasizing their importance as target symptoms for early intervention. Given these findings, improving sleep should be considered a crucial aspect of early treatment.