Pathophysiological mechanism of seasonal affective disorder

The effect of bright light therapy on major depressive disorder: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

The increasing prevalence of major depressive disorder (MDD) has led to increased demand for psychotherapy and pharmacotherapy, yet concerns were raised regarding the cost and accessibility to these therapies. Bright light therapy (BLT) has shown promise in mitigating depressive symptoms of non-seasonal affective disorders. This meta-analysis gathered evidence from randomised controlled trials (RCTs) to assess the effectiveness of BLT on patients with non-seasonal MDD.

METHODS

Five databases were systematically searched. The primary outcome of the meta-analysis was the endpoint depression score from the BLT and control treatment groups, with the remission and response rates as the secondary outcomes. Results are presented in standardised mean difference (SMD) and log odd ratio. Subgroup analyses compared the effects of trial length and the length of daily exposure.

RESULTS

Results on 15 RCTs between 1996 and 2024 with 883 patients showed positive effects of BLT on alleviating depressive symptoms (SMD = 0.48, 95 % CI [0.22, 0.74], p <.001). Trials that lasted two weeks or less or those with 60 minutes or more of daily exposure were associated with higher therapeutic effectiveness. BLT was also associated with a higher response rate at the end of the trial.

CONCLUSION

This meta-analysis offers positive evidence that favours BLT in alleviating depressive symptoms in MDD, suggesting that it could be a convenient and easily accessible treatment modality to augment psychotherapy and pharmacotherapy.

Circadian rhythms-related disorders in diurnal fat sand rats under modern lifestyle conditions: A review

Modern lifestyle reduces environmental rhythmicity and may lead to circadian desynchrony. We are exposed to poor day-time lighting indoors and excessive night-time artificial light. We use air-conditioning to reduce ambient temperature cycle, and food is regularly available at all times. These disruptions of daily rhythms may lead to type 2 diabetes mellitus (T2DM), obesity, cardiometabolic diseases (CMD), depression and anxiety, all of which impose major public health and economic burden on societies. Therefore, we need appropriate animal models to gain a better understanding of their etiologic mechanisms, prevention, and management.We argue that the fat sand rat (Psammomys obesus), a diurnal animal model, is most suitable for studying the effects of modern-life conditions. Numerous attributes make it an excellent model to study human health disorders including T2DM, CMD, depression and anxiety. Here we review a comprehensive series of studies we and others conducted, utilizing the fat sand rat to study the underlying interactions between biological rhythms and health. Understanding these interactions will help deciphering the biological basis of these diseases, which often occur concurrently. We found that when kept in the laboratory (compared with natural and semi-wild outdoors conditions where they are diurnal), fat sand rats show low amplitude, nocturnal or arrhythmic activity patterns, dampened daily glucose rhythm, glucose intolerance, obesity and decreased survival rates. Short photoperiod acclimation exacerbates these pathologies and further dampens behavioral and molecular daily rhythms, resulting in CMD, T2DM, obesity, adipocyte dysfunction, cataracts, depression and anxiety. Increasing environmental rhythmicity by morning bright light exposure or by access to running wheels strengthens daily rhythms, and results in higher peak-to-trough difference in activity, better rhythmicity in clock genes expression, lower blood glucose and insulin levels, improved glucose tolerance, lower body and heart weight, and lower anxiety and depression. In summary, we have demonstrated that fat sand rats living under the correspondent of “human modern lifestyle” conditions exhibit dampened behavioral and biological rhythms and develop circadian desynchrony, which leads to what we have named “The Circadian Syndrome”. Environmental manipulations that increase rhythmicity result in improvement or prevention of these pathologies. Similar interventions in human subjects could have the same positive results and further research on this should be undertaken.

Sleep Interventions in the Treatment of Schizophrenia and Bipolar Disorder

Due to the effects of sleep on the central nervous system, it is thought that sleep disorders have a special importance in the onset, course and treatment of psychiatric diseases. Although the negative effects of sleep problems on the occurrence, recurrence and clinical course of psychiatric disorders are well known, it is reported that clinicians do not spend enough time for sleep problems in practice. This may be related to the fact that patients underreport their complaints for various reasons, insufficient examination time, and clinicians' lack of knowledge about the importance of the subject. Pharmacotherapy, psychological and behavioral interventions are options among the therapeutic approaches to sleep problems. But, it seems that clinicians tend to prefer pharmacological approaches for the treatment of sleep problems. However, it is important to choose the appropriate treatment option with considering the method preferred by the patients, who already use many and high doses of pharmacological agents, the nature of the psychiatric disorder and the sleep problem. In this context, chronotherapeutic approaches such as bright light, sleep deprivation, interpersonal relations and social rhythm therapy, and cognitive behavioral therapy techniques adapted for patients with bipolar disorder can be used in the treatment of suitable patients. In this article, the current literature about sleep-related problems observed in patients with schizophrenia and bipolar disorder is reviewed comprehensively with presenting clinical phenotypes and treatment approaches.

Seasonal Variation in Bright Daylight Exposure, Mood and Behavior among a Group of Office Workers in Sweden

The purpose of the study was to investigate seasonal variation in mood and behavior among a group of office workers in Sweden (56°N). Thirty subjects participated in this longitudinal study. The subjects kept a weekly log that included questionnaires for ratings of psychological wellbeing and daily sleep-activity diaries where they also noted time spent outdoors. The lighting conditions in the offices were subjectively evaluated during one day, five times over the year. There was a seasonal variation in positive affect and in sleep-activity behavior. Across the year, there was a large variation in the total time spent outdoors in daylight. The subjects reported seasonal variation concerning the pleasantness, variation and strength of the light in the offices and regarding the visibility in the rooms. Finally, the subjects spent most of their time indoors, relying on artificial lighting, which demonstrates the importance of the lighting quality in indoor environments.

Genetic Factors Affecting Seasonality, Mood, and the Circadian Clock

In healthy humans, seasonality has been documented in psychological variables, chronotype, sleep, feeding, metabolic and autonomic function, thermoregulation, neurotransmission, and hormonal response to stimulation, thus representing a relevant factor to account for, especially when considering the individual susceptibility to disease. Mood is largely recognized as one of the central aspects of human behavior influenced by seasonal variations. This historical notion, already mentioned in ancient medical reports, has been recently confirmed by fMRI findings, which showed that seasonality in human cognitive brain functions may influence affective control with annual variations. Thus, seasonality plays a major role in mood disorders, affecting psychopathology, and representing the behavioral correlate of a heightened sensitivity to factors influencing circannual rhythms in patients. Although the genetic basis of seasonality and seasonal affective disorder (SAD) has not been established so far, there is growing evidence that factors affecting the biological clock, such as gene polymorphisms of the core clock machinery and seasonal changes of the light-dark cycle, exert a marked influence on the behavior of patients affected by mood disorders. Here we review recent findings about the effects of individual gene variants on seasonality, mood, and psychopathological characteristics.

Treatment of depression with low-strength transcranial pulsed electromagnetic fields: A mechanistic point of view

BACKGROUND

Mood disorders constitute a high burden for both patients and society. Notwithstanding the large arsenal of available treatment options, a considerable group of patients does not remit on current antidepressant treatment. There is an urgent need to develop alternative treatment strategies. Recently, low-strength transcranial pulsed electromagnetic field (tPEMF) stimulation has been purported as a promising strategy for such treatment-resistant depression (TRD). The mode of action of this new technique is however largely unknown.

METHODS

We searched PubMed for literature reports on the effects of tPEMF and for information regarding its working mechanism and biological substrate.

RESULTS

Most studies more or less connect with the major hypotheses of depression and concern the effects of tPEMF on brain metabolism, neuronal connectivity, brain plasticity, and the immune system. Relatively few studies paid attention to the possible chronobiologic effects of electromagnetic fields.

LIMITATIONS

We reviewed the literature of a new and still developing field. Some of the reports involved translational studies, which inevitably limits the reach of the conclusions.

CONCLUSION

Weak magnetic fields influence divergent neurobiological processes. The antidepressant effect of tPEMF may be specifically attributable to its effects on local brain activity and connectivity.

Bright white light therapy in depression: A critical review of the evidence

BACKGROUND

Light therapy is an accepted treatment option, at least for seasonal affective disorder (SAD). Our aim was to critically evaluate treatment effects of bright white light (BWL) on the depressive symptoms in both SAD and non-seasonal depression.

METHODS

The systematic review was performed according to the PRISMA guidelines. PubMed, Embase, and PsycINFO were searched (December 1974 through June 2014) for randomized controlled trials published in peer-reviewed journals. Study quality was assessed with a checklist developed by the Swedish Council on Technology Assessment in Health Care. Only studies with high or medium quality were used in the meta-analyses.

RESULTS

Eight studies of SAD and two studies of non-seasonal depression met inclusion and quality criteria. Effects on SAD were estimated in two meta-analyses. In the first, week by week, BWL reached statistical significance only at two and three weeks of treatment (Standardized Mean Difference, SMD: -0.50 (-CI 0.94, -0.05); -0.31 (-0.59, -0.03) respectively). The second meta-analysis, of endpoint data only, showed a SMD of -0.54 (CI: -0.95, -0.13), which indicates an advantage for BWL. No meta-analysis was performed for non-seasonal depression due to heterogeneity between studies.

LIMITATIONS

This analysis is restricted to short-term effects of BWL measured as mean changes in scores derived from SIGH-SAD, SIGH-SAD self-report, or HDRS rating scales.

CONCLUSIONS

Most studies of BWL have considerable methodological problems, and the results of published meta-analyses are highly dependent on the study selection. Even though quality criteria are introduced in the selection procedures of studies, when the results are carefully scrutinized, the evidence is not unequivocal.

Bright light therapy protects women from circadian rhythm desynchronization during chemotherapy for breast cancer

Circadian rhythms (CRs) are commonly disrupted in women undergoing chemotherapy for breast cancer (BC). Bright light improves and strengthens CRs in other populations. This randomized controlled study examined the effect of morning administration of bright light therapy on CRs in women undergoing chemotherapy for BC. It was hypothesized that women receiving bright light therapy would exhibit more robust rhythms than women exposed to dim light. Thirty-nine women newly diagnosed with BC and scheduled for chemotherapy were randomized into 2 groups: bright white light (BWL) or dim red light (DRL). Women were instructed to use the light box every morning for 30 min during their first 4 cycles of chemotherapy. Wrist actigraphy was recorded at 5 time points: prior to chemotherapy (baseline), Cycle-1 treatment week (C1TW), Cycle-1 recovery week (C1RW), Cycle-4 treatment week (C4TW), and Cycle-4 recovery week (C4RW). There was a Group × Time interaction at C4TW compared to baseline such that the DRL group showed significant deterioration in the mean of the activity rhythm (mesor) and amplitude, whereas the BWL group exhibited a significant increase in both mesor and amplitude. The DRL group also exhibited significant deterioration in overall rhythm robustness at C1TW, C4TW, and C4RW. Women in the BWL group also showed significant decreases in overall rhythm robustness at C1TW and C4TW, but returned to baseline levels at both recovery weeks. The results suggest that morning administration of bright light may protect women from experiencing CR deterioration during chemotherapy.

Should it matter when we record? Time of year and time of day as factors influencing frontal EEG asymmetry

Resting frontal encephalographic (EEG) asymmetry, often conceptualized as a trait marker for depression, is influenced by occasion-specific factors, including time of year and the time of day of the recording session as demonstrated recently (Peterson and Harmon-Jones, 2009). The current study examined the influence of seasonal and chronological variables on resting frontal asymmetry, and also assessed whether different reference montages or surface transformations were equally susceptible to these influences. In a direct replication attempt, contrary to previous findings, no simple time of year by time of day interaction was found. Time awake at recording, however, was an important moderating variable of the relationship between photoperiod and time of day. EEG asymmetry scores based on current-source density (CSD) transformed data, however, appeared less vulnerable to these influences, providing further evidence to suggest that the CSD transform may be advantageous for examining stable trait estimates of frontal EEG asymmetry.

Is Collegiate Athletic Participation a Protective Factor in Seasonality?

This study investigated seasonality in male and female college athletes and nonathletes. Given the literature on activity level and its positive impact on mood, it was predicted that athletes would benefit more than nonathletes with regards to seasonal symptoms. Participants completed measures of seasonality, depression, and cognitive processes during a winter month. Multiple measures of seasonality were administered to distinguish seasonal depression symptoms from nonseasonal symptoms. Results indicated that nonathletes reported more seasonal symptoms, seasonal attitudes, and rumination, gained more weight, socialized the least, and slept more than athletes. Female nonathletes reported the most impact from the changing seasons and more negative thoughts about the changing seasons. These results indicate that engaging in collegiate athletics may serve as a protective factor in seasonal depression.

Cognitive vulnerability in moderate, mild, and low seasonality

This study examined the association between cognitive vulnerability factors and seasonality. Students (N = 88), classified based on the Seasonal Pattern Assessment Questionnaire as experiencing moderate (n = 26) or mild (n = 32) seasonality, and nondepressed, low-seasonality controls (n = 30) completed explicit (i.e., dysfunctional attitudes, automatic negative thoughts, seasonal attitudes, and rumination) and implicit (i.e., implicit associations test) measures of cognitive vulnerability at one winter and one nonwinter assessment. Relative to low- and mild-seasonality participants, moderate-seasonality participants endorsed more automatic thoughts and rumination in winter and more dysfunctional attitudes across both seasons. Moderate- and mild-seasonality participants endorsed more maladaptive seasonal attitudes than did low-seasonality participants. All groups demonstrated increased dysfunctional attitudes, automatic thoughts, and rumination and stronger implicit associations about light and dark during the winter. The findings support a possible cognitive mechanism of winter depression onset and/or maintenance unique to individuals with moderate, as opposed to mild, seasonality.

Seasonality and winter-type seasonal depression are associated with the rs731779 polymorphism of the serotonin-2A receptor gene

Seasonal Affective Disorder (SAD), seasonality and increased sensitivity to the fluctuation of seasons in biological and psychological parameters can manifest to varying degrees across a normal population. The serotonin-2A (5-HT2A) receptor gene has long been suggested as a candidate for the genetic basis of this phenomenon. We hypothesized that functional sequence variation in this gene could contribute to seasonality and the development of winter- and/or summer-type seasonal depression. Seasonality was measured by the self-rating Global Seasonality Score (GSS) of the Seasonal Pattern Assessment Questionnaire, and SAD by the Seasonal Health Questionnaire (SHQ). We analysed associations between GSS or SAD scores and 5-HTR2A receptor gene polymorphisms rs731779, rs985934 and rs6311, in 609 individuals. People carrying the GG genotype of rs731779 were six times more likely to manifest winter or summer SAD compared to GT or TT genotypes (OR = 6.47), and the chance of having winter-type SAD was almost nine-fold (OR = 8.7) with the GG genotype. GG subjects of rs731779 also scored significantly higher on the GSS scale compared to carriers of the T allele. In the haplotype analysis subjects carrying the G allele of rs731779 scored higher on the GSS scale, while the presence of the T allele leads to lower scores. These results suggest that variations in the 5-HTR2A gene play a significant role in the development of seasonality and especially in winter-type SAD. The fact that the above polymorphism showed association not only with clinical SAD but also seasonality symptoms in a general population provides evidence for the spectrum nature of this connection.

A controlled trial of the Litebook light-emitting diode (LED) light therapy device for treatment of Seasonal Affective Disorder (SAD)

BACKGROUND

Recent research has emphasized that the human circadian rhythm system is differentially sensitive to short wavelength light. Light treatment devices using efficient light-emitting diodes (LEDs) whose output is relatively concentrated in short wavelengths may enable a more convenient effective therapy for Seasonal Affective Disorder (SAD).

METHODS

The efficacy of a LED light therapy device in the treatment of SAD was tested in a randomized, double-blind, placebo-controlled, multi-center trial. Participants aged 18 to 65 with SAD (DSM-IV major depression with seasonal pattern) were seen at Baseline and Randomization visits separated by 1 week, and after 1, 2, 3 and 4 weeks of treatment. Hamilton Depression Rating Scale scores (SIGH-SAD) were obtained at each visit. Participants with SIGH-SAD of 20 or greater at Baseline and Randomization visits were randomized to active or control treatment: exposure to the Litebook LED treatment device (The Litebook Company Ltd., Alberta, Canada) which delivers 1,350 lux white light (with spectral emission peaks at 464 nm and 564 nm) at a distance of 20 inches or to an inactivated negative ion generator at a distance of 20 inches, for 30 minutes a day upon awakening and prior to 8 A.M.

RESULTS

Of the 26 participants randomized, 23 completed the trial. Mean group SIGH-SAD scores did not differ significantly at randomization. At trial end, the proportions of participants in remission (SIGH-SAD less than 9) were significantly greater (Fisher's exact test), and SIGH-SAD scores, as percent individual score at randomization, were significantly lower (t-test), with active treatment than with control, both in an intent-to-treat analysis and an observed cases analysis. A longitudinal repeated measures ANOVA analysis of SIGH-SAD scores also indicated a significant interaction of time and treatment, showing superiority of the Litebook over the placebo condition.

CONCLUSION

The results of this pilot study support the hypothesis that light therapy with the Litebook is an effective treatment for SAD.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT00139997.

The association between seasonal and premenstrual symptoms is continuous and is not fully accounted for by depressive symptoms

Seasonal affective disorder (SAD) frequently co-occurs with premenstrual dysphoric disorder. Explanations of this comorbidity highlighting the cyclical nature of female sex hormones imply that seasonal and premenstrual symptoms should correlate positively even in nonclinical samples. In a sample of 91 female college students, we found a sizable positive correlation (r = .45; p < 0.001) between seasonal and premenstrual symptoms. This relation held up even in a subsample selected on the basis of not qualifying for SAD or subsyndromal SAD on a screening measure. Although the correlation was reduced when depressive symptom severity was statistically controlled, it remained positive and significant. Future research testing possible explanations of the co-occurrence of seasonal and premenstrual symptoms should incorporate the full range of severity on symptom variables, treating them as continua rather than solely as binary categories.

The effect of colored illumination on heart rate variability

BACKGROUND

We investigated the effects of illumination with colored fluorescent light on heart rate variability (HRV) and autonomic regulation. Previous examinations have only focused on full-spectrum fluorescent bright light as it is used for the therapy of seasonal affective disorder and disturbances of circadian rhythms.

MATERIALS AND METHODS

In 3 experiments, 12 healthy volunteers were exposed for 10 min to red, green and blue fluorescent light of 700 lux, respectively. These illumination periods were followed and preceded by 15 min of darkness. HRV series were recorded within the last minutes of each illumination and darkness period. HRV analysis encompassed time domain variables, frequency domain variables and detrended fluctuation analysis (DFA).

RESULTS

DFA yielded a highly significant increase of the self-similarity parameter aDFA under red and green illumination, while blue light was accompanied by a decrease. A spectral analysis revealed parallel behavior of very low frequency components in the range of 0.003-0.04 Hz. Green light also seemed to induce a reduction in high frequency components.

CONCLUSIONS

Results show that colored light can influence HRV within minutes and that the effects of individual colors can be distinguished by HRV analysis.

Update on the biology of seasonal affective disorder

The etiology and pathophysiology of seasonal affective disorder (SAD) has been linked to the seasons and to light since its first conceptualization. Aspects of SAD that make it particularly amenable to biological investigation include the predictable recurrent episodes, the rapid response to a nonpharmacologic treatment, the specific neurovegetative features, and the availability of rich animal models of seasonality. This paper reviews new findings for the major biological hypotheses for SAD, focusing on circadian rhythms, neurotransmitters, and molecular genetics. Integrative issues and future directions for the study of SAD, including the heuristic value of a dual-vulnerability hypothesis that conceptualizes seasonality as a dimensional construct and the importance of studying endophenotypes, will be discussed.

Seasonality and seasonal affective disorder (SAD): an evolutionary viewpoint tied to energy conservation and reproductive cycles

The characteristic symptoms of SAD, including hypersomnia and weight gain, might reflect a genetically programmed attempt to conserve energy during historically predictable periods of dwindling food supply. While this basic hypothesis has obvious conceptual appeal, few authors have considered the specific positive selection pressures that might have contributed to such a process. The goal of the current paper is to further develop an evolutionary model of SAD with a focus on energy conservation in the context of seasonal reproductive cycles. To accomplish this, seasonal data on birth rates are considered from an evolutionary viewpoint. There is considerable indirect evidence that in temperate climates, the symptoms of SAD reflect a predisposition for conception to occur in late spring/early summer to ensure a peak of births in the late winter/early spring. The adaptive value of such a pattern, and its putative role in natural selection in humans, is also discussed.

Treatment of seasonal affective disorder: unipolar versus bipolar differences

Evidence-based treatments for seasonal affective disorder (SAD) include light therapy and pharmacotherapy. We briefly review the diagnosis and treatment of SAD, focusing on clinical and treatment differences between patients with unipolar and bipolar illness. Special considerations for the management of SAD in patients with bipolar disorder are discussed, including the need to monitor for emergence of manic and hypomanic mood switches, to use mood stabilizers in patients with bipolar I disorder, and to be aware of potential interactions between bright light and medications used in treating bipolar disorder. Chronobiological treatments such as bright light therapy may be combined with pharmacotherapy to enhance therapeutic effects, reduce adverse side effects, and optimize treatment in patients with seasonal and nonseasonal bipolar disorder.

Does neuroimmune dysfunction mediate seasonal mood changes in winter depression?

BACKGROUND

Animal studies have demonstrated seasonal changes in immune function mediated by nocturnal melatonin duration as a biological signal for photoperiod. Recent research has highlighted the potential role of neuroimmune dysfunction in depressive disorders. The etiology of winter depression (seasonal affective disorder, or SAD) is not known, but a number of studies have provided support for both photoperiod and neurotransmitter hypotheses.

HYPOTHESIS

A new hypothesis is presented that links the SAD data on melatonin, photoperiod, and neurotransmitters by proposing that seasonal increases in proinflammatory cytokines are critical in the pathophysiology of winter SAD.

TESTING THE HYPOTHESIS

In SAD patients, but not healthy subjects: proinflammatory cytokines will be increased and the Th1/Th2 balance will be shifted to the left in winter compared to summer; neuroimmune function will be correlated with nocturnal melatonin duration in SAD patients; and light treatment will correct neuroimmune dysfunction.

IMPLICATIONS OF THE HYPOTHESIS

Diagnostic tests for SAD may be developed using cytokine assays; neuroimmune dysfunction may be predictors of response to treatments; new treatments for SAD (immune or anti-inflammatory treatment) may be developed.

Seasonal affective disorder: an overview

Seasonal Affective Disorder (SAD) is a condition of regularly occurring depressions in winter with a remission the following spring or summer. In addition to depressed mood, the patients tend to experience increased appetite and an increased duration of sleep during the winter. SAD is a relatively common condition, affecting 1-3% of adults in temperate climates, and it is more prevalent in women. The pathological mechanisms underlying SAD are incompletely understood. Certain neurotransmitters have been implicated; a dysfunction in the serotonin system in particular has been demonstrated by a variety of approaches. The role of circadian rhythms in SAD needs to be clarified. The phase-delay hypothesis holds that SAD patients' circadian rhythms are delayed relative to the sleep/wake or rest/activity cycle. This hypothesis predicts that the symptoms of SAD will improve if the circadian rhythms can be phase-advanced. There is some experimental support for this. SAD can be treated successfully with light therapy. In classical light therapy, the SAD sufferer sits in front of a light box, exposed to 2000-10,000 lux for 30-120 min daily during the winter. Other forms of light treatments, pharmacotherapy, and other therapies are currently being tested for SAD.

Cognitive-behavioral factors in seasonal affective disorder

To longitudinally examine cognitive-behavioral correlates of seasonal affective disorder (SAD), the authors assessed women with a history of SAD and nondepressed, matched controls across fall, winter, and summer. SAD history participants reported more automatic negative thoughts throughout the year than controls and demonstrated a progression from decreased activity enjoyment during fall to reduced activity frequency during winter. Ruminative response style, measured in fall, predicted symptom severity during the winter. Across assessments, SAD history women endorsed greater depressive affect in response to low light intensity stimuli than to bright or ambiguous intensity stimuli, but less depressed mood to bright light stimuli than controls. These results suggest that the cognitive-behavioral factors related to nonseasonal depression may play a role in SAD.

Dawn simulation and bright light in the treatment of SAD: a controlled study

BACKGROUND

Some small controlled studies have found that dawn simulation is effective in treating seasonal affective disorder (SAD). With a larger sample size and a longer duration of treatment, we compared dawn simulation with bright light therapy and a placebo condition in patients with SAD.

METHOD

Medication-free patients with SAD were randomly assigned to one of three conditions: bright light therapy (10,000 lux for 30 min, from 6:00 AM to 6:30 AM), dawn simulation (1.5 hour dawn signal from 4:30 AM to 6:00 AM peaking at 250 lux), and a placebo condition, a dim red light (1.5 hour dawn signal from 4:30 am to 6:00 AM peaking at 0.5 lux.) Over the subsequent 6 weeks, the subjects were blindly rated by a psychiatrist using the Structured Interview Guide for the Hamilton Depression Rating-Seasonal Affective Disorder Version (SIGH-SAD). We modeled the profiles of the remissions (SIGH-SAD < or = 8) and response (> or =50% decrease in SIGH-SAD) to treatment over time using Cox proportional hazards models.

RESULTS

The sample consisted of 95 subjects who were randomized to the three conditions: bright light (n = 33), dawn simulation (n = 31) and placebo (n = 31). Dawn simulation was associated with greater remission (p <.05) and response (p <.001) rates compared to the placebo. Bright light did not differ significantly from the placebo. Dawn simulation was associated with greater remission (p <.01) and response (p <.001) rates compared to the bright light therapy. The mean daily hours of sunshine during the week before each visit were associated with a significant increase in likelihood of both remission (p <.001) and response (p <.001).

CONCLUSIONS

Dawn simulation was associated with greater remission and response rates compared to the placebo and compared to bright light therapy. The hours of sunshine during the week before each assessment were associated with a positive clinical response.

Bright light therapy of subsyndromal seasonal affective disorder in the workplace: morning vs. afternoon exposure

OBJECTIVE

Bright light therapy in seasonal affective disorder (SAD) has been studied extensively. However, little attention has been given to subsyndromal seasonal affective disorder (SSAD) or the use of bright light in the workplace. Many patients using bright light boxes complain of the inconvenience of use. Much of this inconvenience involves the often-recommended early timing of the bright light therapy. Patients, who already have difficulty awakening, often have difficulty using the bright light therapy soon after awakening before going to work. If bright light could be used effectively in the workplace, the treatment would be more convenient; the improved convenience would probably improve compliance. In this study, we studied the effectiveness of bright light therapy in subjects with SSAD in the workplace, comparing morning bright light with afternoon bright light.

METHOD

Morning and afternoon bright light treatment (2500 lux) were compared in 30 subsyndromal seasonal affective disorder patients using the bright light therapy in the workplace. Hamilton Depression Ratings and subjective measures of mood, energy, alertness and productivity were assessed before and after 2 weeks of light therapy.

RESULTS

Both morning and evening bright light significantly decreased the depression ratings and improved the subjective mood, energy, alertness and productivity scores. However, there were no significant differences between the two times of administration of the bright light treatment. Both bright light treatments were well tolerated.

CONCLUSION

Bright light given in the workplace improves subjective ratings of mood, energy, alertness and productivity in SSAD subjects. Morning and afternoon bright lights resulted in similar levels of improvement.

Seasonality, social zeitgebers and mood variability in entrainment of mood. Implications for seasonal affective disorder

BACKGROUND

Seasonal variations in mood (seasonality) appear to be entrained to light, a physical zeitgeber. We hypothesised that people high in seasonality may be responsive to a range of zeitgebers, because of greater mood variability. We investigated whether the moods of people high in seasonality were more strongly entrained to the calendar week, a social zeitgeber, and whether any such effect was dependent on variability of mood.

METHODS

53 participants (14 male, 39 female; overall mean age=30) completed a daily mood report, over 56 consecutive days. Participants also completed the Seasonality Score Index (SSI) of the Seasonal Pattern Assessment Questionnaire. Each participant's time series of daily mood was analysed by spectral analysis to quantify the strength of their weekly mood cycle.

RESULTS

Participants with high SSI scores (> or =11) had significantly stronger weekly mood cycles than those with low SSI scores (<11), and significantly greater variability in mood. Covarying for mood variability reduced the difference between high and low SSI groups in mean strength of weekly mood cycle to non-significance.

LIMITATIONS

The time series of moods obtained was relatively short, and moods among high seasonal participants may have been affected by seasonal weather variability.

CONCLUSIONS

People high in seasonality appear to be more responsive to external zeitgebers, and this could be linked to their greater variability in mood. The integration of research on mood variability with research on SAD appears to be warranted.

Suppression of melatonin by 2000-lux light in humans with closed eyelids

BACKGROUND

In order to clarify the role of light in regulating body functions in sleeping humans, we studied whether the light-sensitive pineal hormone melatonin can be suppressed by facial light exposure in subjects with closed eyelids.

METHODS

Eight healthy volunteers participated in 3 nightly sessions: a dim-light control session (< 10 lux) and two light-exposure sessions (2000 lux, 60 min between 2400 and 0200 h). One light exposure occurred with eyes open and the other with eyes closed. Saliva samples were collected at least every hour from 1900 to 0300 h. Melatonin concentrations were measured by radioimmunoassay.

RESULTS

Salivary melatonin concentrations decreased only in 2 of the 8 volunteers during light-exposure sessions with eyes closed. On average, light exposure did not decrease the salivary melatonin concentration.

CONCLUSIONS

Because indoor illuminance is usually much lower than 2000 lux, light is probably ineffective in regulating the neuroendocrine hypothalamic functions in people during their sleep. Nevertheless, the possibility remains that higher illuminances, often used for therapeutic purposes, can inhibit the secretion of melatonin even in sleeping patients.

Dehydroepiandrosterone and Melatonin: Two Neurohormones

Complementary or alternative medicines in the United States have received prominent attention during recent years. Though there seems to be little rigorous support for the long-term efficacy and safety of these treatments in humans,1-2 the popularity of these natural products persists. It has been estimated that, for 1997, 12 percent of the U.S. population (approximately 24 million people) had used herbal medicines within the previous 12 months, and that 5 billion dollars had been spent on these products during that same year.3 Two of the alternative medicines included are dehydroepiandrosterone (DHEA) and melatonin. DHEA is a hormone produced primarily by the adrenal glands, and is a precursor for endogenous steroid production (e.g., testosterone, estrogen). DHEA is also believed to exert central pharmacologic effects. Melatonin is a hormone produced by the pineal gland and is involved in circadium rhythm maintenance and sleep regulation. Because of extensive physiological effects, these two neuro-hormones are being advocated for the treatment of several medical disorders, as well as for routine ailments. The purpose of this article is to discuss salient, pharmacotherapeutic-related characteristics of each hormone, and to briefly review supporting evidence from studies using human subjects.

Dose-response relationship of phototherapy for seasonal affective disorder: a meta-analysis

OBJECTIVE

The therapeutic effect of phototherapy for seasonal affective disorder (SAD) has been widely investigated. However, the antidepressant effect of various light intensities is inconclusive. The purpose of this study was to evaluate the dose-response relationship of phototherapy for SAD.

METHOD

A meta-analytical methodology was applied to 39 studies of phototherapy for SAD. The studies collected were screened for study quality by a threats-to-validity method before inclusion. The fixed-effects-model analysis of variance procedures were used for data analysis.

RESULTS

The results indicated that different light intensities produced different effects in reducing the typical symptoms, as measured by the Hamilton Depression Rating Scale, of patients with SAD. However, no significant differences in these effects were revealed between strong, medium and dim light in reducing the atypical symptoms of patients.

CONCLUSION

These findings showed that light intensity varied positively with the antidepressant effect for typical but not for atypical symptoms of SAD, suggesting that light intensity tended to have different therapeutic effects on the typical and atypical symptoms of SAD.

On abandoning life when it is least difficult

Suicide data from Sweden (1911-1993) and New Zealand (1975-1995) were used to test a hypothesis derived as an extension of the Seasonal Affective Disorder concept. Contrary to the hypothesis, but similar to what Durkheim had reported regarding Central Europe in the nineteenth century, suicides peaked in late spring (May in Sweden, November in New Zealand). Durkheim's hypothesis that there would be more monthly variation in suicides in rural areas was strongly supported. Our hypothesis is that people abandon life when it is least difficult because of a disjuncture between experience and expectation.