One-tenth of the population suffers from insomnia, increasing their risk on other health problems such as depression. Self-reported sleep quality only was historically leading for insomnia diagnosis, but more recently a state of 24-hour hyperarousal has been associated with insomnia, either physiological (increased heart rate, higher frequency EEG) or predominant cognitive-emotional hyperarousal (worry, rumination, repetitive thoughts). Strong evidence shows that those suffering from insomnia with physiological hyperarousal are at higher risk of short and long term severe health problems such as inflammation and hypertension than the group without physiological hyperarousal. The neurophysiological basis of these insomnia phenotypes has however barely been investigated, although its results can have major consequences for how this limiting condition will be treated.