People with insomnia reporting poorer sleep compared to estimates obtained from objective assessments is common across both research and clinical settings. Typically, individuals report less sleep and more wakefulness across a given sleep opportunity compared to that captured via objective methods (e.g. polysomnography) [1–3]. Many different terms have been used to describe this phenomenon since the 1970s , including but not limited to the following: sleep misperception , sleep-state misperception , sleep-state discrepancy , subjective-objective sleep discrepancy , sleep misestimation , and paradoxical-  and pseudo-insomnia . The mechanisms underlying this phenomenon are not yet well understood  and require future research to inform developments in the diagnosis and treatment (or management) of the disorder. The aim of this letter is to facilitate such work by highlighting recent findings and proposing a new nomenclature to become standard practice for describing this phenomenon.
- sleep misperception
- sleep-wake state discrepancy