[Delayed sleep phase syndrome. The most frequent cause of primary chronic insomnia?]

During the past four years the author has seen six cases of chronic persistent insomnia with onset in childhood. Four of these cases had delayed sleep phase syndrome, a disturbance in sleep-wake schedule characterized by the inability to fall asleep, and by continuous sleep of normal length later in the night. The article describes the case histories of two adolescent patients and experience from using chronotherapy. It appeared that chronotherapy was effective, but the demands on the sleep-wake schedule discipline were difficult to accept. It is suggested that delayed sleep phase syndrome may be the most frequent cause of chronic insomnia with onset in childhood.