Hansen T, Bratlid T, Lingjärde O, Brenn T
Acta Psychiatr Scand. 1987 Apr;75(4):428-34. doi: 10.1111/j.1600-0447.1987.tb02811.x.
"Midwinter insomnia" (MI), mainly characterized by difficulties in falling asleep at night, is a common complaint during the period of obscuration or "dark period" north of the arctic circle. We hypothesize that MI is a result of a phase delay of the sleep-wake cycle due to insufficient exposure to daylight. In the present study based on this hypothesis, we wanted to find out whether otherwise healthy subjects with MI show abnormalities in the endocrine markers melatonin and cortisol late in the evening, and whether exposure to intensive light for one half hour in the morning for 5 days has any effect on the insomnia and on the endocrine variables. Nine subjects with typical MI were compared to eight controls. Before light exposure, the MI group had a significantly lower level of plasma melatonin in the evening than the controls, and a nonsignificant increase of plasma cortisol. After light exposure, the following results were seen in the MI group: sleep latency was moderately but significantly shortened, plasma melatonin increased to the same level as in the controls, and there was a nonsignificant increase of plasma cortisol. These results are largely in accordance with the predictions made from the phase delay hypothesis. However, other explanations cannot be ruled out.
“仲冬失眠症”（MI）主要表现为夜间入睡困难，是北极圈以北昏暗期或“黑暗期”常见的一种症状。我们推测，MI是由于日照不足导致睡眠-清醒周期相位延迟的结果。基于这一假设，在本研究中，我们想弄清楚，患有MI的健康受试者在傍晚时，其褪黑素和皮质醇这两种内分泌标志物是否存在异常，以及连续5天每天早晨接受半小时强光照射是否对失眠症及内分泌变量有任何影响。我们将9名典型MI患者与8名对照组进行了比较。在光照前，MI组傍晚时血浆褪黑素水平显著低于对照组，血浆皮质醇水平有不显著的升高。光照后，MI组出现了以下结果：睡眠潜伏期适度但显著缩短，血浆褪黑素升高至与对照组相同水平，血浆皮质醇有不显著的升高。这些结果在很大程度上与相位延迟假设的预测相符。然而，其他解释也不能排除。
