Late, but not early, wake therapy reduces morning plasma melatonin: relationship to mood in Premenstrual Dysphoric Disorder

Sleep-light interventions that shift melatonin rhythms earlier improve perimenopausal and postmenopausal depression: preliminary findings

OBJECTIVE

Testing the hypothesis that a sleep-light intervention, which phase-advances melatonin rhythms, will improve perimenopausal-postmenopausal (P-M; by follicle-stimulating hormone) depression.

METHODS

In at-home environments, we compared two contrasting interventions: (1) an active phase-advance intervention: one night of advanced/restricted sleep from 9 pm to 1 am , followed by 8 weeks of morning bright white light for 60 min/d within 30 minutes of awakening, and (2) a control phase-delay intervention: one night of delayed/restricted sleep (sleep from 3 to 7 am ) followed by 8 weeks of evening bright white light for 60 min/d within 90 minutes of bedtime. We tested 17 P-M participants, 9 normal controls and 8 depressed participants (DPs) (by Diagnostic and Statistical Manual of Mental Disorders [Fifth Edition] criteria). Clinicians assessed mood by structured interviews and subjective mood ratings. Participants wore actigraphs to measure sleep and activity and collected overnight urine samples for the melatonin metabolite, 6-sulfatoxymelatonin (6-SMT), before, during, and after interventions.

RESULTS

Baseline depressed mood correlated with delayed 6-SMT offset time (cessation of melatonin metabolite [6-SMT] secretion) ( r = +0.733, P = 0.038). After phase-advance intervention versus phase-delay intervention, 6-SMT offset (start of melatonin and 6-SMT decrease) was significantly advanced in DPs (mean ± SD, 2 h 15 min ± 12 min; P = 0.042); advance in 6-SMT acrophase (time of maximum melatonin and 6-SMT secretion) correlated positively with mood improvement ( r = +0.978, P = 0.001). Mood improved (+70%, P = 0.007) by both 2 and 8 weeks.

CONCLUSIONS

These preliminary findings reveal significantly phase-delayed melatonin rhythms in DP versus normal control P-M women. Phase-advancing melatonin rhythms improves mood in association with melatonin advance. Thus, sleep-light interventions may potentially offer safe, rapid, nonpharmaceutical, well-tolerated, affordable home treatments for P-M depression.

Critically-timed sleep+light interventions differentially improve mood in pregnancy vs. postpartum depression by shifting melatonin rhythms

BACKGROUND

Testing the hypothesis that combined wake + light therapy improves mood in pregnant vs. postpartum depressed participants (DP) by differentially altering melatonin and sleep timing.

METHODS

Initially 89 women, 37 pregnant (21 normal controls-NC; 16 DP) and 52 postpartum (27 NCs; 25 DP), were randomized to a parallel trial of a phase-delay intervention (PDI): 1-night of early-night wake therapy (sleep 3-7 am) + 6-weeks of evening bright white light (Litebook Advantage) for 60 min starting 90 min before bedtime, vs. a Phase-advance intervention (PAI): 1-night of late-night wake therapy (sleep 9 pm-1 am) + 6-weeks of morning bright white light for 60 min within 30 min of wake time. Blinded clinicians assessed mood weekly by structured interview, and participants completed subjective ratings, a Morningness-Eveningness questionnaire, actigraphy, and collected 2 overnight urine samples for 6-sulphatoxy melatonin (6-SMT).

RESULTS

In pregnant DP, mood improved more after the PDI vs. PAI (p = .016), whereas in postpartum DP, mood improved more after the PAI vs. PDI (p = .019). After wake therapy, 2 weeks of light treatment was as efficacious as 6 weeks (p > .05). In postpartum DP, PAI phase-advanced 6-SMT offset and acrophase (p < .05), which correlated positively with mood improvement magnitude (p = .003).

LIMITATIONS

Small N.

CONCLUSIONS

Mood improved more after 2 weeks of the PDI in pregnant DP, but more after 2 weeks of PAI in postpartum DP in which improvement magnitude correlated with 6-SMT phase-advance. Thus, critically-timed Sleep + Light Interventions provide safe, efficacious, rapid-acting, well-tolerated, at-home, non-pharmaceutical treatments for peripartum DP.

A 1-week sleep and light intervention improves mood in premenstrual dysphoric disorder in association with shifting melatonin offset time earlier

To test the hypothesis that 1 week of combined sleep and light interventions (SALI), which phase-advance (shift earlier) melatonin circadian rhythms, improves mood significantly more than phase-delay (shift later) SALI. After a 2-month diagnostic evaluation for premenstrual dysphoric disorder (PMDD per DSM-5 criteria) in a university clinical research setting, 44 participants enrolled in baseline studies were randomized in the luteal phase at home to (A) a phase-advance intervention (PAI): 1 night of late-night wake therapy (LWT: sleep 9 pm-1 am) followed by 7 days of the morning (AM) bright white light (BWL), or (B) a phase-delay intervention (PDI): 1 night of early-night wake therapy (EWT: sleep 3-7 am) plus 7 days of the evening (PM) BWL. After a month of no intervention, participants underwent the alternate intervention. Outcome measures were mood, the melatonin metabolite, 6-sulfatoxymelatonin (6-SMT), and actigraphy (to assess protocol compliance). At baseline, atypical depression correlated positively with phase delay in 6-SMT offset time (r = .456, p = .038). PAI advanced 6-SMT offset from baseline more than PDI (p < .05), and improved raw mood scores more than PDI (p < .05). As hypothesized, percent improvement in mood correlated positively with a phase advance from baseline in 6-SMT offset time (p < .001). Treatment with 1 night of advanced/restricted sleep followed by 7 days of AM BWL (PAI) was more efficacious in reducing PMDD depression symptoms than a PDI; mood improvement occurred in association with phase advance in 6-SMT offset time. Combined SALIs offer safe, efficacious, rapid-acting, well-tolerated, non-pharmacological, non-hormonal, affordable, repeatable home interventions for PMDD. Clinical Trials.gov NCT # NCT01799733.

Melatonin for premenstrual syndrome: A potential remedy but not ready

Premenstrual syndrome (PMS), a recurrent and moderate disorder that occurs during the luteal phase of the menstrual cycle and quickly resolves after menstruation, is characterized by somatic and emotional discomfort that can be severe enough to impair daily activities. Current therapeutic drugs for PMS such as selective serotonin reuptake inhibitors are not very satisfying. As a critical pineal hormone, melatonin has increasingly been suggested to modulate PMS symptoms. In this review, we update the latest progress on PMS-induced sleep disturbance, mood changes, and cognitive impairment and provide possible pathways by which melatonin attenuates these symptoms. Moreover, we focus on the role of melatonin in PMS molecular mechanisms. Herein, we show that melatonin can regulate ovarian estrogen and progesterone, of which cyclic fluctuations contribute to PMS pathogenesis. Melatonin also modulates gamma-aminobutyric acid and the brain-derived neurotrophic factor system in PMS. Interpreting the role of melatonin in PMS is not only informative to clarify PMS etiology but also instructive to melatonin and its receptor agonist application to promote female health. As a safe interaction, melatonin treatment can be effective in alleviating symptoms of PMS. However, symptoms such as sleep disturbance, depressive mood, cognitive impairment are not specific and can be easily misdiagnosed. Connections between melatonin receptor, ovarian steroid dysfunction, and PMS are not consistent among past studies. Before final conclusions are drawn, more well-organized and rigorous studies are recommended.

An Emerging Role for Sigma-1 Receptors in the Treatment of Developmental and Epileptic Encephalopathies

Developmental and epileptic encephalopathies (DEEs) are complex conditions characterized primarily by seizures associated with neurodevelopmental and motor deficits. Recent evidence supports sigma-1 receptor modulation in both neuroprotection and antiseizure activity, suggesting that sigma-1 receptors may play a role in the pathogenesis of DEEs, and that targeting this receptor has the potential to positively impact both seizures and non-seizure outcomes in these disorders. Recent studies have demonstrated that the antiseizure medication fenfluramine, a serotonin-releasing drug that also acts as a positive modulator of sigma-1 receptors, reduces seizures and improves everyday executive functions (behavior, emotions, cognition) in patients with Dravet syndrome and Lennox-Gastaut syndrome. Here, we review the evidence for sigma-1 activity in reducing seizure frequency and promoting neuroprotection in the context of DEE pathophysiology and clinical presentation, using fenfluramine as a case example. Challenges and opportunities for future research include developing appropriate models for evaluating sigma-1 receptors in these syndromic epileptic conditions with multisystem involvement and complex clinical presentation.

Insomnia and menopause: a narrative review on mechanisms and treatments

The menopausal transition is associated with an increased frequency of sleep disturbances. Insomnia represents one of the most reported symptoms by menopausal women. According to its pathogenetic model (3-P Model), different predisposing factors (i.e. a persistent condition of past insomnia and aging per se) increase the risk of insomnia during menopause. Moreover, multiple precipitating and perpetuating factors should favor its occurrence across menopause, including hormonal changes, menopausal transition stage symptoms (i.e. hot flashes, night sweats), mood disorders, poor health and pain, other sleep disorders and circadian modifications. Thus, insomnia management implies a careful evaluation of the psychological and somatic symptoms of the individual menopausal woman by a multidisciplinary team. Therapeutic strategies encompass different drugs but also behavioral interventions. Indeed, cognitive behavioral therapy represents the first-line treatment of insomnia in the general population, regardless of the presence of mood disorders and/or vasomotor symptoms (VMS). Different antidepressants seem to improve sleep disturbances. However, when VMS are present, menopausal hormone therapy should be considered in the treatment of related insomnia taking into account the risk-benefit profile. Finally, given its good tolerability, safety, and efficacy on multiple sleep and daytime parameters, prolonged-released melatonin should represent a first-line drug in women aged ≥ 55 years.

Comorbid Premenstrual Dysphoric Disorder in Women with Bipolar Disorder: Management Challenges

Bipolar disorder (BD) and premenstrual dysphoric disorder (PMDD) are two cyclic mood illnesses, sometimes presenting together. Their comorbidity appears to be linked to common biological mechanisms and usually results in more severity of mood symptoms and a poorer long-term outcome. Nevertheless, the management of comorbid PMDD/BD has been scarcely studied. Therefore, the aim of the present paper was to review the published literature on the treatment of comorbid PMDD/BD and to provide point-by-point hypotheses to address these complex clinical cases. We searched PubMed to identify the studies focused on the treatment and management of comorbid PMDD/BD using the following search words, alone and in combination: premenstrual dysphoric disorder, bipolar disorder, comorbid, treatment, management, pharmacotherapy, psychotherapy. The search was conducted on the 1st of June 2019 and yielded 55 records. Four papers met our inclusion/exclusion criteria and were therefore included in our qualitative synthesis. Integrating the few data pertaining to the treatment of comorbid PMDD/BD with the large amount of published data on the two conditions separately, we can suggest that the management of comorbid PMDD/BD needs as a first step to stabilize the bipolar symptoms by means of optimal dosages of mood stabilizers. Then, in euthymic BD patients, the PMDD symptoms could be treated with estroprogestins (first-line treatment). On the contrary, during acute phases of BD, antidepressants (for major depressive episodes) and atypical antipsychotics/hormonal modulators (for manic episodes) could be considered as promising add-on treatments to mood stabilizers. In case of resistant PMDD/BD symptoms, combined strategies should be taken into account, as well as alternative treatments, such as lifestyle changes. In conclusion, RCTs on comorbid PMDD/BD are still lacking. The management of this complex condition is therefore challenging and it requires a tailored treatment.

Early versus late wake therapy improves mood more in antepartum versus postpartum depression by differentially altering melatonin-sleep timing disturbances

BACKGROUND

Peripartum major depression (MD) disables mothers and impairs emotional and neurocognitive development of offspring. We tested the hypothesis that critically-timed wake therapy (WT) relieves peripartum MD by altering melatonin and sleep timing, differentially, in antepartum vs. postpartum depressed patients (DP).

METHODS

In a university clinical research center, we initially randomized 50 women - 26 antepartum (17 healthy comparison-HC, 9 DP) and 24 postpartum (8 HC, 16 DP) - to a cross-over trial of one night of early-night wake therapy (EWT: sleep 3:00-7:00 am) vs. late-night wake therapy (LWT: sleep 9:00 pm-01:00 am). Ultimately, we obtained mood, overnight plasma melatonin and polysomnography for: 15 antepartum women receiving EWT, 18 receiving LWT; 15 postpartum women receiving EWT, 14 receiving LWT.

RESULTS

EWT improved mood more in antepartum vs. postpartum DP in conjunction with reduced (normalized) melatonin-sleep phase-angle differences (PADs) due to delayed melatonin onsets and advanced sleep onsets, and increased (from baseline) total sleep times (TST). LWT improved mood more in postpartum vs. antepartum DP in conjunction with increased TST.

LIMITATIONS

Small samples potentially rendered the study underpowered to detect group differences, making confirmation with larger samples essential. Sufficient follow-up data were not available in most women to document the duration of the mood response to wake therapy.

CONCLUSIONS

EWT benefitted antepartum DP more by realigning melatonin and sleep timing, whereas LWT benefitted postpartum DP more by increasing TST. Thus, consistent with precision medicine aims, maximum mood benefits accrue from timing sleep/wake interventions to specific peripartum circadian pathophysiologies.

Sleep and Premenstrual Syndrome

The etiology of premenstrual syndrome (PMS) is unknown; it may be due to the normal effect of hormones during the menstrual cycle as it occurs in the late luteal phase of the menstrual cycle.PMS affects women of childbearing age and remits with the onset of menstruation. The menstrual phase is known to influence stage 2 and REM sleep in women, irrespective of premenstrual dysphoric disorder (PMDD). Women with PMDD showed a decreased response to melatonin in their luteal phase as compared to the follicular phase of the menstrual cycle. However, melatonin duration or timing of offset in the morning has not been reported to correlate with the mood. Rather, improvement in mood-related symptoms of PMDD has been found to be influenced by sleep deprivation, be it sleep restrictions in early or late night. Sleep disturbance and decreased melatonin secretions due to hormonal fluctuations during the luteal phase of the menstrual cycle could explain the sleep complaints of PMDD.

Photoperiodic and circadian bifurcation theories of depression and mania

Seasonal effects on mood have been observed throughout much of human history.  Seasonal changes in animals and plants are largely mediated through the changing photoperiod (i.e., the photophase or duration of daylight).  We review that in mammals, daylight specifically regulates SCN (suprachiasmatic nucleus) circadian organization and its control of melatonin secretion.  The timing of melatonin secretion interacts with gene transcription in the pituitary pars tuberalis to modulate production of TSH (thyrotropin), hypothalamic T3 (triiodothyronine), and tuberalin peptides which modulate pituitary production of regulatory gonadotropins and other hormones.  Pituitary hormones largely mediate seasonal physiologic and behavioral variations.  As a result of long winter nights or inadequate illumination, we propose that delayed morning offset of nocturnal melatonin secretion, suppressing pars tuberalis function, could be the main cause for winter depression and even cause depressions at other times of year.  Irregularities of circadian sleep timing and thyroid homeostasis contribute to depression.  Bright light and sleep restriction are antidepressant and conversely, sometimes trigger mania.  We propose that internal desynchronization or bifurcation of SCN circadian rhythms may underlie rapid-cycling manic-depressive disorders and perhaps most mania.  Much further research will be needed to add substance to these theories.

Treatment of premenstrual dysphoric disorder

Premenstrual dysphoric disorder (PMDD) is comprised of a cluster of affective, behavioral and somatic symptoms recurring monthly during the luteal phase of the menstrual cycle. The disorder affects 3-8% of menstruating women and represents the more severe and disabling end of the spectrum of premenstrual disorders, which includes premenstrual syndrome and premenstrual aggravation of underlying affective disorder. Rigorous and specific diagnostic criteria for PMDD were specified in the Diagnostic and Statistical Manual of Mental Disorders IV (1994) and reaffirmed in the Diagnostic and Statistical Manual of Mental Disorders V (2013) and, consequently, there has been a marked increase in well-designed, placebo-controlled studies evaluating treatment modalities. Although the exact pathogenesis of PMDD is still elusive, treatment of PMDD and severe premenstrual syndrome has centered on neuromodulation via serotonin reuptake inhibitor antidepressants, and ovulation suppression utilizing various contraceptive and hormonal preparations. Unlike the approach to the treatment of depression, serotonergic antidepressants need not be given daily, but can be effective when used cyclically, only in the luteal phase or even limited to the duration of the monthly symptoms. Less, well-substantiated alternative treatments, such as calcium supplementation, agnus castus (chasteberry), Hypericum perforatum (St John's wort) and cognitive/behavioral/relaxation therapies, may be useful adjuncts in the treatment of PMDD. This review provides an overview of current information on the treatment of PMDD.

Polysomnographic evaluation of sleep quality and quantitative variables in women as a function of mood, reproductive status, and age

This archival cross-sectional investigation examined the impact of mood, reproductive status (RS), and age on polysomnographic (PSG) measures in women. PSG was performed on 73 normal controls (NC) and 64 depressed patients (DP), in the course of studies in menstruating, pregnant, postpartum, and peri- and postmenopausal women. A two-factor, between-subjects multivariate analysis of variance (MANOVA) was used to test the main effects of reproductive status (RS: menstrual vs pregnant vs postpartum vs menopausal) and diagnosis (NC vs DP), and their interaction, on PSG measures. To further refine the analyses, a two-factor, between subjects MANOVA was used to test the main effects of age (19 to 27 vs 28 to 36 vs 37 to 45 vs 46+ years) and diagnosis on the PSG data. Analyses revealed that in DP women, rapid eye movement (REM) sleep percentage was significantly elevated relative to NC across both RS and age. Significant differences in sleep efficiency, Stage 1%, and REM density were associated with RS; differences in total sleep time, Stage 2 percentage, and Stage 4 percentage were associated with differences in age. Both RS and age were related to differences in sleep latency, Stage 3 percentage, and Delta percentage. Finally, wake after sleep onset time, REM percentage, and REM latency did not vary with respect to RS or age. Overall, this investigation examined three major variables (mood, RS, and age) that are known to impact sleep in women. Of the variables, age appeared to have the greatest impact on PSG sleep measures, reflecting changes occurring across the lifespan.

ISPMD consensus on the management of premenstrual disorders

The second consensus meeting of the International Society for Premenstrual Disorders (ISPMD) took place in London during March 2011. The primary goal was to evaluate the published evidence and consider the expert opinions of the ISPMD members to reach a consensus on advice for the management of premenstrual disorders. Gynaecologists, psychiatrists, psychologists and pharmacologists each formally presented the evidence within their area of expertise; this was followed by an in-depth discussion leading to consensus recommendations. This article provides a comprehensive review of the outcomes from the meeting. The group discussed and agreed that careful diagnosis based on the recommendations and classification derived from the first ISPMD consensus conference is essential and should underlie the appropriate management strategy. Options for the management of premenstrual disorders fall under two broad categories, (a) those influencing central nervous activity, particularly the modulation of the neurotransmitter serotonin and (b) those that suppress ovulation. Psychotropic medication, such as selective serotonin reuptake inhibitors, probably acts by dampening the influence of sex steroids on the brain. Oral contraceptives, gonadotropin-releasing hormone agonists, danazol and estradiol all most likely function by ovulation suppression. The role of oophorectomy was also considered in this respect. Alternative therapies are also addressed, with, e.g. cognitive behavioural therapy, calcium supplements and Vitex agnus castus warranting further exploration.

Pilot investigation of the circadian plasma melatonin rhythm across the menstrual cycle in a small group of women with premenstrual dysphoric disorder

Women with premenstrual dysphoric disorder (PMDD) experience mood deterioration and altered circadian rhythms during the luteal phase (LP) of their menstrual cycles. Disturbed circadian rhythms may be involved in the development of clinical mood states, though this relationship is not fully characterized in PMDD. We therefore conducted an extensive chronobiological characterization of the melatonin rhythm in a small group of PMDD women and female controls. In this pilot study, participants included five women with PMDD and five age-matched controls with no evidence of menstrual-related mood disorders. Participants underwent two 24-hour laboratory visits, during the follicular phase (FP) and LP of the menstrual cycle, consisting of intensive physiological monitoring under “unmasked”, time-isolation conditions. Measures included visual analogue scale for mood, ovarian hormones, and 24-hour plasma melatonin. Mood significantly (P≤.03) worsened during LP in PMDD compared to FP and controls. Progesterone was significantly (P = .025) increased during LP compared to FP, with no between-group differences. Compared to controls, PMDD women had significantly (P<.05) decreased melatonin at circadian phases spanning the biological night during both menstrual phases and reduced amplitude of its circadian rhythm during LP. PMDD women also had reduced area under the curve of melatonin during LP compared to FP. PMDD women showed affected circadian melatonin rhythms, with reduced nocturnal secretion and amplitude during the symptomatic phase compared to controls. Despite our small sample size, these pilot findings support a role for disturbed circadian rhythms in affective disorders. Possible associations with disrupted serotonergic transmission are proposed.

Polysomnographic evaluation of sleep quality and quantitative variables in women as a function of mood, reproductive status, and age

This archival cross-sectional investigation examined the impact of mood, reproductive status (RS), and age on polysomnographic (PSG) measures in women. PSG was performed on 73 normal controls (NC) and 64 depressed patients (DP), in the course of studies in menstruating, pregnant, postpartum, and peri- and postmenopausal women. A two-factor, between-subjects multivariate analysis of variance (MANOVA) was used to test the main effects of reproductive status (RS: menstrual vs pregnant vs postpartum vs menopausal) and diagnosis (NC vs DP), and their interaction, on PSG measures. To further refine the analyses, a two-factor, between subjects MANOVA was used to test the main effects of age (19 to 27 vs 28 to 36 vs 37 to 45 vs 46+ years) and diagnosis on the PSG data. Analyses revealed that in DP women, rapid eye movement (REM) sleep percentage was significantly elevated relative to NC across both RS and age. Significant differences in sleep efficiency, Stage 1%, and REM density were associated with RS; differences in total sleep time, Stage 2 percentage, and Stage 4 percentage were associated with differences in age. Both RS and age were related to differences in sleep latency, Stage 3 percentage, and Delta percentage. Finally, wake after sleep onset time, REM percentage, and REM latency did not vary with respect to RS or age. Overall, this investigation examined three major variables (mood, RS, and age) that are known to impact sleep in women. Of the variables, age appeared to have the greatest impact on PSG sleep measures, reflecting changes occurring across the lifespan.

The relationship of nocturnal melatonin to estradiol and progesterone in depressed and healthy pregnant women

PURPOSE

To assess the relationship between nocturnal plasma melatonin and serum estradiol (E(2)) and progesterone (P(4)) levels in depressed pregnant women (DW) and matched healthy women (HW).

METHODS

We used analysis of variance (ANOVA) and linear regression analyses on data obtained from pregnant HW and DW.

RESULTS

Log E(2) and log P(4) were positively correlated with measures of melatonin quantity in HW (p<0.05) but not DW, controlling for age. Log E(2) and log P(4) were positively correlated with melatonin offset and duration in DW (p<0.01) but not HW.

CONCLUSIONS

Pregnant DW may be less sensitive than HW to modulation of melatonin secretion by E(2) and P(4). That melatonin timing measures are more sensitive to E(2) and P(4) variation in DW may reflect a circadian system more attuned to the need for realignment in DW than in HW. These altered sensitivities to reproductive hormones may reflect a biologic vulnerability that predisposes some pregnant women to depression.

Reduced phase-advance of plasma melatonin after bright morning light in the luteal, but not follicular, menstrual cycle phase in premenstrual dysphoric disorder: an extended study

The authors previously observed blunted phase-shift responses to morning bright light in women with premenstrual dysphoric disorder (PMDD). The aim of this study was to determine if these findings could be replicated using a higher-intensity, shorter-duration light pulse and to compare these results with the effects of an evening bright-light pulse. In 17 PMDD patients and 14 normal control (NC) subjects, the authors measured plasma melatonin at 30-min intervals from 18:00 to 10:00 h in dim (<30 lux) or dark conditions the night before (Night 1) and after (Night 3) a bright-light pulse (administered on Night 2) in both follicular and luteal menstrual cycle phases. The bright light (either 3000 lux for 6 h or 6000 lux for 3 h) was given either in the morning (AM light), 7 h after the dim light melatonin onset (DLMO) measured the previous month, or in the evening (PM light), 3 h after the DLMO. In the luteal, but not in the follicular, phase, AM light advanced melatonin offset between Night 1 and Night 3 significantly less in PMDD than in NC subjects. The effects of PM light were not significant, nor were there significant effects of the light pulse on melatonin measures of onset, duration, peak, or area under the curve. These findings replicated the authors' previous finding of a blunted phase-shift response to morning bright light in the luteal, but not the follicular, menstrual cycle phase in PMDD compared with NC women, using a brighter (6000 vs. 3000 lux) light pulse for a shorter duration (3 vs. 6 h). As the effect of PM bright light on melatonin phase-shift responses did not differ between groups or significantly alter other melatonin measures, these results suggest that in PMDD there is a luteal-phase subsensitivity or an increased resistance to morning bright-light cues that are critical in synchronizing human biological rhythms. The resulting circadian rhythm malsynchonization may contribute to the occurrence of luteal phase depressive symptoms in women with PMDD.