Five insomnia subtypes identified in a study
Five subtypes of insomnia disorder were identified by investigators from The Netherlands, addressing an unmet need to reduce the heterogeneity of insomnia disorder.
In the study, participants from the Netherlands Sleep Registry (n=4,322) recruited between March 2010 and October 2016 were followed up using a questionnaire to survey traits, life events and health history. Analysis revealed five novel insomnia disorder subtypes: highly distressed, moderately distressed but reward sensitive, moderately distressed and reward insensitive, slightly distressed with high reactivity, and slightly distressed with low reactivity. [Lancet Psychiatry 2019, doi: 10.1016/S2215-0366(18)30513-3]
Among patients who were reassessed 4.8 years later (n=215), the probability of maintaining their original insomnia subtype was 0.87.
“The characteristics we focused on have been shown to be rooted in brain function and structure, and are therefore stable over time,” said investigator Miss Tessa Blanken of the Department of Sleep and Cognition, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands.
Subtype 1 was termed highly distressed insomnia disorder (19 percent of the participants), which was characterized by high pre-sleep arousal, negative affect and reduced subjective happiness (p<0.0001).
Subtype 2 was termed moderately distressed, reward sensitive insomnia disorder (31 percent of the participants), and was characterized by moderate general distress, pre-sleep arousal, insomnia response to stress and negative affect (p<0.0001). Participants classified under this subtype favoured positive rumination and experiences of pleasure.
In contrast, subtype 3 (moderately distressed, reward insensitive insomnia disorder; 15 percent of the participants) is characterized mainly by reduced subjective happiness with the lowest degree of positive affect, positive rumination and experience of pleasure (p<0.0001) compared with the other subtypes.
Subtype 4 (slightly distressed, high reactive insomnia disorder; 20 percent of participants) is characterized by a longer duration of insomnia response to life events, frequent childhood trauma and fatigue (p<0.0001).
Subtype 5 (slightly distressed, low reactive insomnia disorder; 15 percent of participants) is characterized by reduced behavioural activation, reduced experience of pleasure and fatigue (p<0.0001). This subtype is also characterized by the onset of insomnia later in life, such as above 40 years of age.
“The classification also showed important differences in the way each group responds to common treatments,” added Blanken.
Those who were classified as subtype 2 reported that cognitive behavioural therapy (CBT) alleviated their symptoms of insomnia (mean change in score, -0.8; p=0.0003). In comparison, the other four subtypes reported absence of changes in their sleep patterns with CBT. Benzodiazepine treatment led to resolution of symptoms in subtypes 2 and 4, but did not have any effect on the other subtypes.
The prevalence of lifetime depression (54.3 percent; p<0.05), anxiety (37 percent; p<0.05), and bipolar disorder (4.9 percent p<0.05) was shown to be highest in the first subtype.
“Subtyping of insomnia disorder facilitates identification of the underlying causes, development of personalized treatments, and selection of patients with the highest risk of depression for inclusion in trials on prevention of depression,” the investigators concluded.
Insomnia disorder is reported to be the second most prevalent mental health disorder after anxiety disorders. [Eur Neuropsychopharmacol 2011;21:655–679] Genome-wide association studies have reported that insomnia disorder is more closely related to mood, personality and well-being than to sleep-related phenotypes. [Nat Genet 2017;49:1584-1592; bioRxiv 2018;214973]