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What Are The Effects of Insomnia and Springtime

What Are The Effects of Insomnia and Springtime

Q.

What are the effects of springtime and its increased availability of sunlight on sleep?

Response from  Douglas E Moul, MD 
Assistant Professor, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Medical Director, Ward 8, Western Psychiatric Institute and Clinic, Pittsburgh, Pennsylvania

A.

The answer to this question might be viewed from 3 different perspectives: known human seasonal biology, epidemiology, and clinical awareness.

As the question supposes, there is good evidence that human beings have seasonal biology, just like the other kinds of large primates. Wehr and colleagues[1] performed studies of human subjects, who were required to remain in absolute darkness for 14 hours per day for approximately a month. This mimics a light/dark cycle that other creatures are exposed to in natural environments during winter at moderately northern latitudes. The study demonstrated that the period of melatonin secretion expanded, as occurs in other animals. The subjects did not have insomnia, but tended to experience a period in the middle of the night when they stayed in bed awake. This was consistent with the 2-process model of sleep regulation,[2] whereby the first bout of sleep was more related to the sleep pressure developed during the period of prior daytime wakefulness, whereas the second was more due to the circadian factor that normally increases sleep propensity from 3:00-5:00 AM. Similar natural-world findings were noted by Bratlid and Wahlund.[3] In winter-depression patients, however, the period of nocturnal melatonin secretion may be more sensitive.[4] Overall, these highly controlled studies only tell us so much if we wish to generalize about the population as a whole.

In most modern-world circumstances, humans have great control over their light/dark cycles using natural lighting sources. So in a strict sense, the effects of spring, considered as a time of increased light, are confounded by other controls that humans have over their light environment. The influence of temperature on human sleep is probably similarly confounded by the fact that humans often control the temperatures of the environments in which they live, and, unlike many other creatures, can promptly manage the thermal properties of their skin coverings. An additional consideration is that seasonality and circadian rhythms may be more important biologically early in life during the reproductive years rather than during old age, because the seasons govern the fertility cycles of many animals. Sleep normally becomes shallower and more fragmented with age in any case, and there is evidence that there is some decrement in the amplitude of biological rhythms in old age.[5] One would suspect that there is less seasonal sensitivity to insomnia in old age, although one study suggests that non-winter seasonality is greater in the aged.[6]

Insomnia and Springtime

What Are The Effects of Insomnia and Springtime

Q.

What are the effects of springtime and its increased availability of sunlight on sleep?

Response from  Douglas E Moul, MD 
Assistant Professor, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Medical Director, Ward 8, Western Psychiatric Institute and Clinic, Pittsburgh, Pennsylvania

A.

The answer to this question might be viewed from 3 different perspectives: known human seasonal biology, epidemiology, and clinical awareness.

As the question supposes, there is good evidence that human beings have seasonal biology, just like the other kinds of large primates. Wehr and colleagues[1] performed studies of human subjects, who were required to remain in absolute darkness for 14 hours per day for approximately a month. This mimics a light/dark cycle that other creatures are exposed to in natural environments during winter at moderately northern latitudes. The study demonstrated that the period of melatonin secretion expanded, as occurs in other animals. The subjects did not have insomnia, but tended to experience a period in the middle of the night when they stayed in bed awake. This was consistent with the 2-process model of sleep regulation,[2] whereby the first bout of sleep was more related to the sleep pressure developed during the period of prior daytime wakefulness, whereas the second was more due to the circadian factor that normally increases sleep propensity from 3:00-5:00 AM. Similar natural-world findings were noted by Bratlid and Wahlund.[3] In winter-depression patients, however, the period of nocturnal melatonin secretion may be more sensitive.[4] Overall, these highly controlled studies only tell us so much if we wish to generalize about the population as a whole.

In most modern-world circumstances, humans have great control over their light/dark cycles using natural lighting sources. So in a strict sense, the effects of spring, considered as a time of increased light, are confounded by other controls that humans have over their light environment. The influence of temperature on human sleep is probably similarly confounded by the fact that humans often control the temperatures of the environments in which they live, and, unlike many other creatures, can promptly manage the thermal properties of their skin coverings. An additional consideration is that seasonality and circadian rhythms may be more important biologically early in life during the reproductive years rather than during old age, because the seasons govern the fertility cycles of many animals. Sleep normally becomes shallower and more fragmented with age in any case, and there is evidence that there is some decrement in the amplitude of biological rhythms in old age.[5] One would suspect that there is less seasonal sensitivity to insomnia in old age, although one study suggests that non-winter seasonality is greater in the aged.[6]

Conducting epidemiologic studies to answer this question definitively would be very difficult. The methods required would include not only getting a large, representative sample, but also following that sample at least quarterly through the year. To my knowledge, candidate studies are the Epidemiological Catchment Area study, NHANES, or possibly the National Comorbidity Survey. None to date has approached the methodologic requirements. Even in the epidemiology of major depression, a syndrome that often includes insomnia as a symptom, the findings about the seasonality of depression are variable. One study has proposed that the prevalence of winter depression is 7% in mid-northern latitudes;[7] however, this figure is too high to be consistent with several other well-regarded studies.[8] In short, the whole question of the seasonality of insomnia and depression in the general population remains unsettled.

However, populations are composed of subgroups. In very northern latitudes, there is evidence that there is a clinical group that suffers from winter insomnia.[6-9] This might be biologically related to the syndrome of winter depression described by Rosenthal and colleagues,[10] with the difference being that winter depressions are usually described as characterized more by hypersomnia rather than insomnia. Whether winter insomnia might be classified as a depression, as a hypomania, or as a variant of primary insomnia is unclear. Among winter-depression patients, however, the hypersomnia of winter tends to go away as spring advances. If the patient is bipolar, he or she may evolve into hyperthymic, hypomanic, or even (more rarely) manic phases during the summer in association with the abeyance of hypersomnia.[11,12] In noting this possibility, though, it is not as though this relationship is firmly established, as a number of studies — for example that of Silverstone and colleagues[13] — fail to confirm any consistent and particular pattern of seasonality in affective illnesses. Nonetheless, should the abeyance of hypersomnia turn into frank insomnia, it may be important to monitor such patients more closely in the spring for manic symptoms. Although insomnia can be a premonitory symptom of impending mania, sleep difficulties are often present even in euthymic bipolar patients,[14] so it is probably unwarranted to conclude that all bipolar patients are at risk in the spring. But some bipolar patients clearly are, making the question about insomnia in the spring an important one to ask regarding the seasonally sensitive patient.

Even without considering seasonality, though, insomnia can be considered a risk marker for the development or recurrence of a variety of mental illnesses.[15] If treating insomnia prevents the development or recurrence of other mental disorders, then doing so would be an example of the targeted primary prevention of mental disorders. In some patients, insomnia and hypersomnia do appear to be linked to seasonality. Thus, assessing the seasonal sensitivity of patients may be an important diagnostic focus for the prevention-minded clinician.

 



References

  1. Wehr TA, Moul DE, Barbato G, Giesen HA, Seidel JA, Barker C, Bender C. Conservation of photoperiod-responsive mechanisms in humans. Am J Physiol. 1993;265(4 pt 2):R846-R857.
  2. Borbely AA, Achermann P: Sleep homeostasis and models of sleep regulation. In: Kryger MH, Roth T, Dement WC, eds. Principles and Practices of Sleep Medicine. Philadelphia: Elsevier; 2005:405-417.
  3. Bratlid T, Wahlund B. Alterations in serum melatonin and sleep in individuals in a sub-arctic region from winter to spring. Int J Circumpolar Health. 2003;62:242-254. Abstract
  4. Wehr TA, Duncan WC Jr, Sher L, et al. A circadian signal of change of season in patients with seasonal affective disorder. Arch Gen Psychiatry. 2001;58:1108-1114. Abstract
  5. Carrier J, Monk TH, Buysse DJ, Kupfer DJ: Amplitude reduction of the circadian temperature and sleep rhythms in the elderly. Chronobiol Int. 1996;13:373-386. Abstract
  6. Husby R, Lingjaerde O: Prevalence of reported sleeplessness in northern Norway in relation to sex, age and season. Acta Psychiatr Scand. 1990;81:542-547. Abstract
  7. Kasper S, Wehr TA, Bartko JJ, Gaist PA, Rosenthal NE. Epidemiological findings of seasonal changes in mood and behavior. A telephone survey of Montgomery County, Maryland. Arch Gen Psychiatry. 1989;46:823-833. Abstract
  8. Regier DA, Kaelber CT, Rae DS, et al. Limitations of diagnostic criteria and assessment instruments for mental disorders. Implications for research and policy. Arch Gen Psychiatry. 1998;55:109-115. Abstract
  9. Lingjaerde O, Bratlid T, Hansen T: Insomnia during the “dark period” in northern Norway. An explorative, controlled trial with light treatment. Acta Psychiatr Scand. 1985;71:506-512. Abstract
  10. Rosenthal NE, Sack DA, Gillin JC, et al. Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy. Arch Gen Psychiatry. 1984;41:72-80. Abstract
  11. Faedda GL, Tondo L, Teicher MH, Baldessarini RJ, Gelbard HA, Floris GF. Seasonal mood disorders. Patterns of seasonal recurrence in mania and depression. Arch Gen Psychiatry. 1993;50:17-23. Abstract
  12. Shapira A, Shiloh R, Potchter O, Hermesh H, Popper M, Weizman A. Admission rates of bipolar depressed patients increase during spring/summer and correlate with maximal environmental temperature. Bipolar Disord. 2004;6:90-93. Abstract
  13. Silverstone T, Romans S, Hunt N, McPherson H. Is there a seasonal pattern of relapse in bipolar affective disorders? A dual northern and southern hemisphere cohort study. Br J Psychiatry. 1995;167:58-60. Abstract
  14. Harvey AG, Schmidt DA, Scarna A, Semler CN, Goodwin GM: Sleep-related functioning in euthymic patients with bipolar disorder, patients with insomnia, and subjects without sleep problems. Am J Psychiatry. 2005;162:50-57. Abstract
  15. State-of-the-Science Panel Draft Report. In: NIH State-of-the Science Conference on Manifestations and Management of Chronic Insomnia in Adults. Bethesda, Md: National Institutes of Health; June 13-15, 2005.

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