Poor daytime functioning is a frequent complaint among those suffering from insomnia. Previous studies have found that their daytime cognitive performance is not significantly degraded, seemingly suggesting it is a perceived issue that does not reflect a real impairment. A new study of individuals with sleep-onset insomnia revealed that the impairment may be real but hidden during the normal day — yet exposed after pulling an all-nighter, which impacted them much more than age-matched control subjects.