Subtyping insomnia disorder

I read with interest the Article by Tessa Blanken and colleagues,1Blanken TF Benjamins JS Borsboom D et al.Insomnia disorder subtypes derived from life history and traits of affect and personality.Lancet Psychiatry. 2019; 6: 151-163Summary Full Text Full Text PDF PubMed Scopus (83) Google Scholar in which the authors identified five novel insomnia disorder subtypes that were differentiated by biologically based traits and life history. In their study, participants with subtype 1 insomnia (highly distressed) showed the highest risk of lifetime depression (88/162 [54·3%]), anxiety (60/162 [37·0%]), and bipolar disorder (8/162 [4·9%]).1Blanken TF Benjamins JS Borsboom D et al.Insomnia disorder subtypes derived from life history and traits of affect and personality.Lancet Psychiatry. 2019; 6: 151-163Summary Full Text Full Text PDF PubMed Scopus (83) Google Scholar Participants with subtype 1 insomnia also showed the highest prevalence of mental and behavioural disorders classified in ICD-10: mood, anxiety, personality, and childhood onset.1Blanken TF Benjamins JS Borsboom D et al.Insomnia disorder subtypes derived from life history and traits of affect and personality.Lancet Psychiatry. 2019; 6: 151-163Summary Full Text Full Text PDF PubMed Scopus (83) Google Scholar Half of the participants classified with subtype 1 insomnia reported difficulty initiating sleep by their teenage years.1Blanken TF Benjamins JS Borsboom D et al.Insomnia disorder subtypes derived from life history and traits of affect and personality.Lancet Psychiatry. 2019; 6: 151-163Summary Full Text Full Text PDF PubMed Scopus (83) Google Scholar In my opinion, some of the participants diagnosed with depression in subtype 1 insomnia could probably also have been diagnosed with bipolar disorder or bipolar spectrum disorder. Bipolar disorder is characterised by fluctuations in mood state and the onset of symptoms occurs during the teenage years.2Grande I Berk M Birmaher B Vieta E Bipolar disorder.Lancet. 2016; 387: 1561-1572Summary Full Text Full Text PDF PubMed Scopus (820) Google Scholar Sleep disturbance and consequent dysregulation of circadian rhythms have been hypothesised to be a central mechanism in the pathophysiology of bipolar disorder or bipolar spectrum disorder, as well as being a predictor of the first onset and subsequent course of bipolar disorder.3Harvey AG Sleep and circadian rhythms in bipolar disorder: seeking synchrony, harmony, and regulation.Am J Psychiatry. 2008; 165: 820-829Crossref PubMed Scopus (415) Google Scholar, 4Alloy LB Ng TH Titone MK Boland EM Circadian rhythm dysregulation in bipolar spectrum disorders.Curr Psychiatry Rep. 2017; 19: 21Crossref PubMed Scopus (76) Google Scholar Therefore, the findings of Blanken and colleagues would be consistent with some of the participants with subtype 1 insomnia having bipolar disorder, but the questionnaires the authors used for classification did not include items that could ascertain this. The authors considered that nearly half of the participants classified with subtype 1 insomnia might have an unknown resilient factor to depression; however, I thought some of the participants had bipolarity and might develop depression intrinsically. I recommend that the authors reanalyse their data to calculate the percentage of the participants in subtype 1 insomnia who had developed a sleep disturbance by their teenage years and then went on to develop depression or bipolar disorder. By this reanalysis, I anticipate that subtype 1 insomnia could be divided into two additional groups on the basis of the presence of bipolarity. I declare no competing interests. Insomnia disorder subtypes derived from life history and traits of affect and personalityHigh-dimensional data-driven subtyping of people with insomnia has addressed an unmet need to reduce the heterogeneity of insomnia disorder. Subtyping facilitates identification of the underlying causes of insomnia, development of personalised treatments, and selection of patients with the highest risk of depression for inclusion in trials regarding prevention of depression. Full-Text PDF Subtyping insomnia disorderWe read with great interest the Article by Tessa Blanken and colleagues,1 in which the authors aimed to identify subtypes of insomnia by means of data-driven analyses on the basis of several biologically based traits. This study is highly relevant since the conception of insomnia as a heterogeneous disease is gaining more and more credit, and might represent a cornerstone by promoting discoveries of new mechanisms and different treatments. Full-Text PDF Subtyping insomnia disorder – Authors' replyWe are grateful for the opportunity to clarify our new insomnia subtypes.1 Luigi Ferini-Strambi and colleagues invite us to address common method bias. Bias by online assessment, if any, cannot underlie differences among subtypes and controls because the bias applies to all equally. Whether participants would be similarly grouped together if subtypes were sought in objective sleep electroencephalogram (EEG) features, rather than in subjectively reported traits, is a different question. We do not propose our subtyping method as a replacement for sleep EEG recordings aimed at revealing other pathological sleep conditions. Full-Text PDF