New research from the Netherlands has identified five different types of insomnia, explaining that this may be the reason it’s been a disorder that’s so hard to treat. Researchers say the finding could be a new page in the history of insomnia, promoting discoveries on mechanisms and interventions.
One out of ten people suffer from chronic insomnia: it’s the second-most prevalent and burdensome mental disorder. Findings on underlying brain mechanisms have been inconsistent. Treatment that is effective for some gives no relief to others. Insomnia has remained an enigma.
With the help of thousands of volunteers, Drs. Tessa Blanken and her colleagues at the Netherlands Institute for Neuroscience now revealed why it has been so difficult to find consistent brain mechanisms and treatment effects.
“While we have always considered insomnia to be one disorder, it actually represents five different disorders,” she said. “Underlying brain mechanisms may be very different. For comparison: progress in our understanding of dementia was propelled once we realized that there are different kinds.”
Surprisingly, the five insomnia types did not differ at all on sleep complaints like difficulty falling asleep versus early morning awakening. Some earlier attempts to define subtypes focused on these sleep complaints, and may therefore have been unsuccessful. Blanken and colleagues assessed dozens of questionnaires on personality traits that are known to be rooted in brain structure and function. Insomnia subtypes could be discovered by looking at trait profiles. Type 1 scores high on many distressing traits such as anxiety and feeling down or tense. Types 2 and 3 experienced less distress and were distinguished by their high versus low sensitivity to reward. Type 4 and 5 experienced even less distress and differed by the way their sleep responded to stressful life events. These induced severe and long-lasting insomnia in type 4, while the sleep of type 5 was unaffected by these events .
Volunteers measured again after five years mostly retained their own type, which suggested anchoring in the brain.
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