The two‐process model of sleep regulation: a reappraisal

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Summary

The two-process model of sleep regulation, integrating homeostatic sleep pressure (Process S) with circadian pacemaker control (Process C), remains the foundational framework for understanding sleep timing and designing light-based interventions. Its principles underpin non-pharmacological psychiatric treatments involving manipulation of circadian phase and light exposure, with direct implications for therapeutic lighting protocols.

Key Findings

The model successfully simulates sleep timing and intensity across diverse experimental protocols over three decades of research.
Process S deficiency is proposed to account for both depressive sleep disturbances and the antidepressant effect of sleep deprivation.
SCN electrophysiological recordings indicate that Process S and Process C interact continuously, not only at sleep–wake transitions.
Peripheral oscillators linked to energy metabolism can dissociate from the central SCN pacemaker, supporting the concept of a sleep/fast and wake/feed cycle that segregates anabolic and catabolic metabolic processes.
The model has supported development of non-pharmacological psychiatric treatments based on manipulating circadian phase, sleep timing, and light exposure.

Categories

Sleep & Circadian Health: The paper reappraises the two-process model (homeostatic Process S + circadian Process C) that governs sleep timing and intensity, directly relevant to understanding and designing light interventions.

Mood & Mental Wellness: The model links Process S deficiency to depressive sleep disturbances and explains the antidepressant mechanism of sleep deprivation and circadian phase manipulation.