In 2001, the ICSD (International Classification of Sleep Disorders) updated their criteria for the diagnosis of idiopathic hypersomnia. Essentially, EDS must be present for at least 6 months, sleep studies (polysomnography and multiple sleep latency test) must show certain characteristics, and all other known causes for long sleep time and EDS must be considered (see hypersomnia).[2] For the patient, this diagnostic process is often tedious, expensive and time-consuming, as other than the sleep studies, it is still basically a diagnosis of exclusion.