Lewy Alfred J, Emens Jonathan S, Songer Jeannie B, Sims Neelam, Laurie Amber L, Fiala Steven C, Buti Allie L
Oregon Health & Science University, Portland, OR; phone: 503-494-7746, fax: 503-494-5329,
Sleep Med Clin. 2009 Jun 1;4(2):285-299. doi: 10.1016/j.jsmc.2009.02.003.
The phase shift hypothesis (PSH) states that most patients with SAD become depressed in the winter because of a delay in circadian rhythms with respect to the sleep/wake cycle: According to the PSH, these patients should preferentially respond to the antidepressant effects of bright light exposure when it is scheduled in the morning so as to provide a corrective phase advance and restore optimum alignment between the circadian rhythms tightly coupled to the endogenous circadian pacemaker and those rhythms that are related to the sleep/wake cycle. Recent support for the PSH has come from studies in which symptom severity was shown to correlate with the degree of circadian misalignment: it appears that a subgroup of patients are phase advanced, not phase delayed; however, the phase-delayed type is predominant in SAD and perhaps in other disorders as well, such as non-seasonal unipolar depression. It is expected that during the next few years the PSH will be tested in these and other conditions, particularly since healthy subjects appear to have more severe symptoms of sub-clinical dysphoria correlating with phase-delayed circadian misalignment; critically important will be the undertaking of treatment trials to investigate the therapeutic efficacy of morning bright light or afternoon/evening low-dose melatonin in these disorders in which symptoms are more severe as the dim light melatonin onset (DLMO) is delayed with respect to the sleep/wake cycle (non-restorative sleep should also be evaluated, as well as bipolar disorder). The possibility that some individuals (and disorders) will be of the phase-advanced type should be considered, taking into account that the correct timing of phase-resetting agents for them will be bright light scheduled in the evening and/or low-dose melatonin taken in the morning. While sleep researchers and clinicians are accustomed to phase-typing patients with circadian-rhythm sleep disorders according to the timing of sleep, phase typing based on the DLMO with respect to the sleep/wake cycle may lead to quite different recommendations for the optimal scheduling of phase-resetting agents, particularly for the above disorders and conditions.
相位偏移假说（PSH）指出，大多数季节性情感障碍（SAD）患者在冬季会出现抑郁，原因是昼夜节律相对于睡眠/觉醒周期出现延迟：根据PSH，这些患者在早晨安排明亮光照时，应优先对其抗抑郁作用产生反应，以便提供一个矫正性的相位提前，并恢复与内源性昼夜节律起搏器紧密耦合的昼夜节律与那些与睡眠/觉醒周期相关的节律之间的最佳同步。最近对PSH的支持来自一些研究，这些研究表明症状严重程度与昼夜节律失调程度相关：似乎有一部分患者是相位提前，而非相位延迟；然而，相位延迟型在SAD中占主导地位，可能在其他疾病中也是如此，比如非季节性单相抑郁症。预计在未来几年，PSH将在这些及其他情况下得到检验，特别是因为健康受试者似乎有更严重的亚临床烦躁症状，这与相位延迟的昼夜节律失调相关；至关重要的是开展治疗试验，以研究早晨明亮光照或下午/晚上低剂量褪黑素对这些疾病的治疗效果，在这些疾病中，随着暗光褪黑素起始（DLMO）相对于睡眠/觉醒周期延迟，症状会更严重（还应评估非恢复性睡眠以及双相情感障碍）。应考虑到一些个体（和疾病）可能是相位提前型，因为对他们而言，相位重置剂的正确给药时间将是晚上安排明亮光照和/或早晨服用低剂量褪黑素。虽然睡眠研究人员和临床医生习惯于根据睡眠时间对患有昼夜节律性睡眠障碍的患者进行相位分型，但基于DLMO相对于睡眠/觉醒周期的相位分型可能会对相位重置剂的最佳给药时间提出截然不同的建议，特别是对于上述疾病和情况。
