Critical interval hypotheses for depression

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.

Cellular Circadian Clocks in Mood Disorders

Bipolar disorder (BD) and major depressive disorder (MDD) are heritable neuropsychiatric disorders associated with disrupted circadian rhythms. The hypothesis that circadian clock dysfunction plays a causal role in these disorders has endured for decades but has been difficult to test and remains controversial. In the meantime, the discovery of clock genes and cellular clocks has revolutionized our understanding of circadian timing. Cellular circadian clocks are located in the suprachiasmatic nucleus (SCN), the brain’s primary circadian pacemaker, but also throughout the brain and peripheral tissues. In BD and MDD patients, defects have been found in SCN-dependent rhythms of body temperature and melatonin release. However, these are imperfect and indirect indicators of SCN function. Moreover, the SCN may not be particularly relevant to mood regulation, whereas the lateral habenula, ventral tegmentum, and hippocampus, which also contain cellular clocks, have established roles in this regard. Dysfunction in these non-SCN clocks could contribute directly to the pathophysiology of BD/MDD. We hypothesize that circadian clock dysfunction in non-SCN clocks is a trait marker of mood disorders, encoded by pathological genetic variants. Because network features of the SCN render it uniquely resistant to perturbation, previous studies of SCN outputs in mood disorders patients may have failed to detect genetic defects affecting non-SCN clocks, which include not only mood-regulating neurons in the brain but also peripheral cells accessible in human subjects. Therefore, reporters of rhythmic clock gene expression in cells from patients or mouse models could provide a direct assay of the molecular gears of the clock, in cellular clocks that are likely to be more representative than the SCN of mood-regulating neurons in patients. This approach, informed by the new insights and tools of modern chronobiology, will allow a more definitive test of the role of cellular circadian clocks in mood disorders.

Circadian typology: a comprehensive review

The interest in the systematic study of the circadian typology (CT) is relatively recent and has developed rapidly in the two last decades. All the existing data suggest that this individual difference affects our biological and psychological functioning, not only in health, but also in disease. In the present study, we review the current literature concerning the psychometric properties and validity of CT measures as well as individual, environmental and genetic factors that influence the CT. We present a brief overview of the biological markers that are used to define differences between CT groups (sleep-wake cycle, body temperature, cortisol and melatonin), and we assess the implications for CT and adjustment to shiftwork and jet lag. We also review the differences between CT in terms of cognitive abilities, personality traits and the incidence of psychiatric disorders. When necessary, we have emphasized the methodological limitations that exist today and suggested some future avenues of work in order to overcome these. This is a new field of interest to professionals in many different areas (research, labor, academic and clinical), and this review provides a state of the art discussion to allow professionals to integrate chronobiological aspects of human behavior into their daily practice.

Rapid-acting antidepressant strategies: mechanisms of action

Current antidepressants are ineffective in many depressed patients. Thus there is an urgent need to develop treatment strategies which have significantly faster response, can be sustained and have minimal side-effects. This paper reviews clinical data, potential biomarkers, mechanisms of action and future research directions for two proven strategies that produce marked improvement in severe depressive symptoms within 48 h, ketamine and sleep deprivation therapy (SDT). These treatments provide unequivocal evidence that the depressive process can be rapidly reversed in a subgroup of patients. Seventeen ketamine studies in over 150 patients showed a rapid response. Low-dose intravenous ketamine produced mild psychotomimetic effects but response has not been effectively sustained. SDT has been investigated in over 60 studies with a 40-60% response rate within 48 h. Although SDT is often used in Europe to initiate a rapid response, it is less utilized within the USA, in part, because it has a short duration when administered alone. We review data concerning chronotherapeutic strategies of bright-light therapy (BLT) and sleep-phase advance (SPA) which successfully sustain the antidepressant efficacy of SDT. Evidence is further discussed that a significant group of mood disorders have abnormal circadian rhythms which are known to be controlled by clock genes. It is hypothesized that chronotherapeutic manipulations can reset clock genes and thus, abnormalities in circadian rhythms. Further findings are reviewed that ketamine, in addition to its role as an NMDA antagonist, can also alter circadian rhythms. Thus, ketamine may share a critical mechanism with SDT.

Depression scores associate with chronotype and social jetlag in a rural population

In public health, mood disorders are among the most important mental impairments. Patients with depressive episodes exhibit daily mood variations, abnormal patterns in sleep-wake behavior, and in the daily rhythms of several endocrine-metabolic parameters. Although the relationship between the sleep/circadian processes and mood disorders is poorly understood, clock-related therapies, such as light therapy, sleep deprivation, and rigid sleep schedules, have been shown to be effective treatments. Several studies investigated the relationship between circadian phenotype (chronotype) and depression. These focused mainly on urban populations and assessed diurnal preferences (Morningness-Eveningness score) rather than the actual timing of sleep and activity. Here, we used the Beck Depression Inventory (BDI) in an essentially rural population (N?=?4051), and investigated its relation to circadian phenotype (chronotype and social jetlag), assessed with the Munich Chronotype Questionnaire (MCTQ). In our study design, we (i) normalized both chronotype and BDI scores for age and sex (MSF(sas) and BDI(as), respectively); (ii) calculated individual social jetlag (misalignment of the biological and social time); and (iii) investigated the relationship between circadian phenotypes and BDI scores in a population homogeneous in respect to culture, socioeconomic factors, and daily light exposure. A 15.65% (N?=?634) of the participants showed mild to severe depressive BDI scores. Late chronotypes had a higher BDI(as) than intermediate and early types, which was independent of whether or not the participants were smokers. Both chronotype and BDI(as) correlated positively with social jetlag. BDI(as) was significantly higher in subjects with >2?h of social jetlag than in the rest of the population?again independent of smoking status. We also compared chronotype and social jetlag distributions between BDI categories (no symptoms, minimal symptoms, and mild to severe symptoms of depression) separately for men and women and for four age groups; specifically in the age group 31?40 yrs, subjects with mild to severe BDI scores were significantly later chronotypes and suffered from higher social jetlag. Our results indicate that misalignment of circadian and social time may be a risk factor for developing depression, especially in 31- to 40-yr-olds. These relationships should be further investigated in longitudinal studies to reveal if reduction of social jetlag should be part of prevention strategies. (Author correspondence: karla.allebrandt@med.uni-muenchen.de ).

Circadian misalignment in mood disturbances

Recent refinements in methodology allow chronobiological researchers to answer the following questions: is there circadian misalignment in sleep and mood disturbances, and, if so, is it of the phase-advance or phase-delay type? Measurement of the dim light melatonin onset-to-midsleep interval, or phase-angle difference, in sleep and mood disorders should answer these questions. Although the phase-advance hypothesis of affective disorders was formulated three decades ago, recent studies suggest that many, if not all, mood disturbances have a circadian misalignment component of the phase-delay type, operationally defined as a delay in the dim light melatonin onset relative to the sleep/wake cycle. Phase-delayed disorders can be treated with bright light in the morning and/or low-dose melatonin in the afternoon/evening. Phase-advanced disorders can be treated with bright light in the evening and/or low-dose melatonin in the morning.

Diminished perception of light as a symptom of depression: further studies

BACKGROUND

In a previous preliminary report, the perception of a decrease in ambient light intensity appeared to be correlated with depression. We prospectively studied this potential link in a controlled study.

METHODS

The question, "I've noticed that the lights in my surroundings seem dimmer than usual", was added to the Center for Epidemiologic Studies Depression Scale (CES-D) questionnaire and administered prospectively to 213 subjects 50-80 years of age participating in the Age-Related Eye Disease Study (AREDS). All had visual acuity of 20/32 or better in at least one eye. Main outcome measures were the relationship between the dimness question answer and severity of depression, and the likelihood that patients reporting dimness were depressed.

RESULTS

Subjects endorsing their surroundings as being dimmer than usual at least some of the time had a mean CES-D score of 10.6 (SD=7.0) compared to a mean of 5.5 (SD=5.4) for subjects who never noted dimness (t=-4.22, p=.0001). Depressed individuals (CES-D > or = 16) were significantly more likely to report dimness than non-depressed (CES-D<16) subjects (chi(2)=15.6, p<0.0001). The total CES-D score and the degree of reported dimness (0-3) were significantly associated (r=0.31, p<.0001). Using a stepwise regression analysis, subjects who reported any dimness were more likely to be depressed.

LIMITATIONS

A relatively small number of subjects, 38 (18%), reported dimness requiring us to dichotomize their dimness level in some analyses.

CONCLUSIONS

Perceived dimness of one's ambient surroundings and clinical depression are linked. Health care professionals should inquire about this symptom in potentially depressed patients.

Diminished perception of ambient light: a symptom of clinical depression?

OBJECTIVE

In a non-randomized, uncontrolled pilot study, the authors investigated whether depressed patients were more likely to perceive the lighting in their environment as being dimmer than usual.

METHOD

120 patients (46 males, 74 females) who presented for possible admission for depression at a psychiatric facility were administered a Diagnostic and Statistical Manual of disorders (DSM-IV) based questionnaire and underwent psychiatric evaluation. A question asking whether 'the lights in my surroundings seem dimmer than usual' was included in the 15-point question survey. Statistical analyses were performed to determine whether an affirmative response to this dimness question was correlated with the depth of depression (mild, moderate, severe) and also whether significant correlation was present between the percentage of patients answering yes to the dimness question versus the number of yes responses to the core symptoms of depression.

RESULTS

Two thirds of the patients categorized as severely depressed responded that their ambient environment appeared dimmer than usual compared to 21% of moderately and 14% of mildly depressed patients. This difference was statistically significant (P<0.05). The degree of depression as determined by the number of core questions answered affirmatively and the presence of this 'dimness' symptom were highly correlated (P=0.002, R=0.87).

LIMITATIONS

The specificity of the finding has not been tested in reference to non-affective psychiatric patient groups.

CONCLUSION

A patient's perception of the ambient light in the environment being dimmer than usual may be an important symptom of a major depressive disorder. Further replication and objective testing of visual function in depressed patients appears warranted.

Temperature rhythm of patients with major affective disorders: reduced circadian period length

The aim of the study was to explore circadian alterations of the temperature rhythm in adults with Major Affective Disorders (DSM III-R:296.xx). The axillary temperature of 56 inpatients was recorded (6-min intervals for at least a 48-h span) when major clinical symptoms occurred and thereafter during the remission. Periods (tau s) of the temperature rhythm were accurately quantified from individual time series by power spectra analyses. Twenty-seven subjects with no affective disorders served as controls. Histograms of the frequency distribution of tau s, chi square, and so forth were used as statistical methods. In both patients and controls a multimodal distribution of prominent tau s was observed. However, in controls this distribution showed the highest frequency (88.9%) with tau s = 24h, and seldom tau s < 24h or tau s > 24h, while in patients with major affective disorders, tau s exhibited a statistically significant (x2 = 10.84; p < 0.004) different distribution with the highest frequency for tau s < 24h in 50% of the patients. Subjects diagnosed as suffering from Major Affective Disorders commonly exhibit a period shorter than 24h in the axillary temperature circadian rhythm suggestive of a desynchronized time structure.

Circadian rhythms and the pharmacology of affective illness

The chronic effects of antidepressant drugs (ADs) on circadian rhythms of behavior, physiology and endocrinology are reviewed. The timekeeping properties of several classes of ADs, including tricyclic antidepressants, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, serotonin agonists and antagonists, benzodiazepines, and melatonin are reviewed. Pharmacological effects on the circadian amplitude and phase, as well as effects on day-night measurements of motor activity, sleep-wake, body temperature (Tb), 3-methoxy-4-hydroxyphenylglycol, cortisol, thyroid hormone, prolactin, growth hormone and melatonin are examined. ADs often lower nocturnal Tb and affect the homeostatic regulation of sleep. ADs often advance the timing and decrease the amount of slow wave sleep, reduce rapid eye movement sleep and increase or decrease arousal. Together, AD effects on nocturnal Tb and sleep may be related to their therapeutic properties. ADs sometimes delay nocturnal cortisol timing and increase nocturnal melatonin, thyroid hormone and prolactin levels; these effects often vary with diagnosis, and clinical state. The effects of ADs on the coupling of the central circadian pacemaker to photic and nonphotic zeitgebers are discussed.

Effect of morning and afternoon naps on mood after total sleep deprivation in patients with major depression

In 30 depressed patients who had responded to total sleep deprivation therapy, morning naps led more frequently to relapses into depression than did afternoon naps. Longer naps were less detrimental than shorter ones, and there was no significant relationship between the effect of a nap on mood and its content of slow-wave-sleep. The amount of the rapid eye-movement sleep, too, was unrelated to clinical nap effects. Thus, some of the current theories on the relationship between sleep and depressive symptomatology are not supported by the data. Our results demonstrate the importance of nap timing, suggesting a circadian variation of propensity to relapse into depression.

Diurnal rhythm of core body temperature is phase advanced in a rodent model of depression

We examined the diurnal rhythm of core body temperature in a strain of rats with an upregulated central muscarinic receptor system. The Flinders-Sensitive Line (FSL) was derived by selectively breeding rats for sensitivity to cholinergic agonists. When compared to control rats, the FSL rats showed a remarkably strong phase advance of the acrophase in body temperature during a standard light-dark schedule. Some patients with some types of depression also show phase advances in a number of circadian rhythms, including temperature. Our finding of a phase advance in a rodent model with a known upregulated muscarinic receptor system is compatible with both the phase advance and the muscarinic overdrive theories of depression. These findings also further validate the usefulness of the FSL rats in the study of depression.

The circadian rhythm of plasma thyrotropin in depression and recovery

The 24-hr patterns of plasma thyrotropin have been observed in 12 endogenous depressed patients in both depressed and recovered states and in 13 normal subjects. A clear circadian rhythm was detected in controls with high values at night. In depression, the circadian rhythm was altered with amplitude reduction and blunted nocturnal secretion, abnormalities particularly relevant in bipolar patients. This flattened profile could be linked to the blunted response of TSH to TRH administration reported in depressed patients. Normal nyctohemeral patterns have been restored after recovery. These chronobiological abnormalities as well as their normalization under antidepressant drugs seem to be similar to those reported for various parameters (e.g. temperature, cortisol, etc) in depression which could support the chronobiological hypothesis for affective disorders.

The effect of antidepressant drugs on 24-hour rhythms of tryptophan metabolism in the rat

The effect of three antidepressant drugs, imipramine hydrochloride, clomipramine hydrochloride and zimelidine dihydrochloride on plasma free and total TRY concentrations has been examined. The drugs were administered to male Wistar rats in the drinking water at a concentration of 200 micrograms ml-1 for up to 15 days. The effects of TRY concentration were complex and, after 2 days, inconsistent. After 14 days, the overall effect of imipramine was to lower free TRY levels and abolish 24-hr variation in free TRY concentration. Zimelidine and clomipramine tended to increase free TRY, particularly at 1300h so that the overall effect was to delay the peak in plasma-free TRY until later in the day. The possible significance of these findings to the mechanism of action of antidepressant drugs in clinical practice is discussed.