Findings on underlying brain mechanisms for insomnia have been inconsistent. Treatment that is effective for some, gives no relief to others. Now researchers at the Netherlands Institute for Neuroscience find there are are 5 distinct types of insomnia.

This finding was published January 7 by The Lancet Psychiatry. A commentary in the journal stated that the finding could be a new page in the history of insomnia, promoting discoveries on mechanisms and interventions.

Tessa Blanken, MSc, and her colleagues at the Netherlands Institute for Neuroscience, say, “While we have always considered insomnia to be one disorder, it actually represents¬†5 different disorders. 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, such as Alzheimer-, vascular-, and frontal-temporal dementia.”

Surprisingly, the 5 insomnia types identified by these researchers did not differ at all on sleep complaints, like difficulty falling asleep versus early morning awakening. Blanken and colleagues instead identified subtypes by looking beyond sleep complaints. They assessed dozens of questionnaires on personality traits that are known to be rooted in brain structure and function, then looking at trait profiles.

Type 1 scores high on many distressing traits such as neuroticism 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 .

After 5 years, participants who were measured again mostly retained their own type, which suggested anchoring in the brain. Indeed, types also differed in their EEG response to environmental stimuli.

Underlying mechanisms can now be better mapped with brain research, the researchers say, adding that subtyping was clinically relevant. Effectiveness of treatment with sleeping pills or cognitive behavioral therapy differed per type. And the risk of developing depression varied dramatically. Subtyping enables much more efficient research into the prevention of depression, by inviting specifically those with the highest risk. The researchers have now started a study into prevention of depression in people with insomnia who run the highest risk.

The institute, in collaborating with other organizations and with the help of volunteers, have launched an internet registry, available at slaapregister.nl, which it hopes will provide a database for faster discoveries in the future.