Impact of genetic variants within serotonin turnover enzymes on human cerebral monoamine oxidase A in vivo

Variants within the monoamine oxidase A (MAO-A, MAOA) and tryptophan hydroxylase 2 (TPH2) genes, the main enzymes in cerebral serotonin (5-HT) turnover, affect risk for depression. Depressed cohorts show increased cerebral MAO-A in positron emission tomography (PET) studies. TPH2 polymorphisms might also influence brain MAO-A because availability of substrates (i.e. monoamine concentrations) were shown to affect MAO-A levels. We assessed the effect of MAOA (rs1137070, rs2064070, rs6323) and TPH2 (rs1386494, rs4570625) variants associated with risk for depression and related clinical phenomena on global MAO-A distribution volume (VT) using [11C]harmine PET in 51 participants (21 individuals with seasonal affective disorder (SAD) and 30 healthy individuals (HI)). Statistical analyses comprised general linear models with global MAO-A VT as dependent variable, genotype as independent variable and age, sex, group (individuals with SAD, HI) and season as covariates. rs1386494 genotype significantly affected global MAO-A VT after correction for age, group and sex (p < 0.05, corr.), with CC homozygotes showing 26% higher MAO-A levels. The role of rs1386494 on TPH2 function or expression is poorly understood. Our results suggest rs1386494 might have an effect on either, assuming that TPH2 and MAO-A levels are linked by their common product/substrate, 5-HT. Alternatively, rs1386494 might influence MAO-A levels via another mechanism, such as co-inheritance of other genetic variants. Our results provide insight into how genetic variants within serotonin turnover translate to the cerebral serotonin system. Clinicaltrials.gov Identifier: NCT02582398. EUDAMED Number: CIV-AT-13-01-009583.

Photoperiodic changes in hippocampal neurogenesis and plasma metabolomic profiles in relation to depression-like behavior in mice

Photoperiod alters affective behaviors and brain neuroplasticity in several mammalian species. We addressed whether neurogenesis and signaling pathways of insulin-like growth factor-I (IGF-I), a key modulator of neuroplasticity, are regulated by photoperiod in C57BL/6 J mice, a putative model of seasonal affective disorder. We also examined the effects of photoperiod on plasma metabolomic profiles in relation to depression-like behavior to understand a possible linkage between peripheral metabolism and behavior. Mice that were maintained under long-day conditions (LD) exhibited a higher number of 5-bromo-2'-deoxyuridine-positive cells and higher levels of astrocyte marker in the dentate gyrus of the hippocampus compared to that of mice under short-day conditions (SD). Plasma IGF-I levels and levels/expression of IGF-I signaling molecules in the hippocampus (Brn-4, NeuroD1, and phospho-Akt) involved in neuronal proliferation and differentiation were higher in the mice under LD. Metabolome analysis using plasma of the mice under LD and SD identified several metabolites that were highly correlated with immobility in the forced swim test, a depression-like behavior. Negative correlations with behavior occurred in the levels of 23 metabolites, including metabolites related to neurogenesis and antidepressant-like effects of exercise, metabolites in the biosynthesis of arginine, and the occurrence of branched chain amino acids. Three metabolites had positive correlations with the behavior, including guanidinosuccinic acid, a neurotoxin. Taken together, photoperiodic responses of neurogenesis and neuro-glial organization in the hippocampus may be involved in photoperiodic alteration of depression-like behavior, mediated through multiple pathways, including IGF-I and peripheral metabolites.

Integrated theory to unify status among schizophrenia and manic depressive illness

Tryptophan hydroxylase 1 is primarily expressed in the gastrointestinal tract, and has been associated with both schizophrenia and depression. Although decreased serotonin activity has been reported in both depression and mania, it is important to investigate the interaction between serotonin and other neurotransmitter systems. There are competitive relationships between branched-chain amino acids, and tryptophan and tyrosine that relate to physical activity, and between L-3,4-dihydroxyphenylalanine (L-DOPA) and 5-hydroxytryptophan (5-HTP), both highly dependent on intracellular tetrahydrobiopterin concentrations. Here, I propose a chaos theory for schizophrenia, mania, and depression using the competitive interaction between tryptophan and tyrosine with regard to the blood-brain barrier and coenzyme tetrahydrobiopterin. Mania may be due to the initial conditions of physical hyperactivity and hypofunctional 5-HTP-producing cells inducing increased dopamine. Depression may be due to the initial conditions of physical hypoactivity and hypofunctional 5-HTP-producing cells inducing decreased serotonin. Psychomotor excitation may be due to the initial conditions of physical hyperactivity and hyperfunctional 5-HTP-producing cells inducing increased serotonin and substantially increased dopamine. The hallucinatory-paranoid state may be due to the initial conditions of physical hypoactivity and hyperfunctional 5-HTP-producing cells inducing increased serotonin and dopamine.

Photoperiodic responses of depression-like behavior, the brain serotonergic system, and peripheral metabolism in laboratory mice

Seasonal affective disorder (SAD) is characterized by depression during specific seasons, generally winter. The pathophysiological mechanisms underlying SAD remain elusive due to a limited number of animal models with high availability and validity. Here we show that laboratory C57BL/6J mice display photoperiodic changes in depression-like behavior and brain serotonin content. C57BL/6J mice maintained under short-day conditions, as compared to those under long-day conditions, demonstrated prolonged immobility times in the forced swimming test with lower brain levels of serotonin and its precursor l-tryptophan. Furthermore, photoperiod altered multiple parameters reflective of peripheral metabolism, including the ratio of plasma l-tryptophan to the sum of other large neutral amino acids that compete for transport across the blood-brain barrier, responses of circulating glucose and insulin to glucose load, sucrose intake under restricted feeding condition, and sensitivity of the brain serotonergic system to peripherally administered glucose. These data suggest that the mechanisms underlying SAD involve the brain-peripheral tissue network, and C57BL/6J mice can serve as a powerful tool for investigating the link between seasons and mood.

Depression-like responses induced by daytime light deficiency in the diurnal grass rat (Arvicanthis niloticus)

Seasonal Affective Disorder (SAD) is one of the most common mood disorders with depressive symptoms recurring in winter when there is less sunlight. The fact that light is the most salient factor entraining circadian rhythms leads to the phase-shifting hypothesis, which suggests that the depressive episodes of SAD are caused by misalignments between the circadian rhythms and the habitual sleep times. However, how changes in environmental lighting conditions lead to the fluctuations in mood is largely unknown. The objective of this study is to develop an animal model for some of the features/symptoms of SAD using the diurnal grass rats Arvichantis niloticus and to explore the neural mechanisms underlying the light associated mood changes. Animals were housed in either a 12∶12 hr bright light∶dark (1000lux, BLD) or dim light∶dark (50lux, DLD) condition. The depression-like behaviors were assessed by sweet-taste Saccharin solution preference (SSP) and forced swimming test (FST). Animals in the DLD group showed higher levels of depression-like behaviors compared to those in BLD. The anxiety-like behaviors were assessed in open field and light/dark box test, however no significant differences were observed between the two groups. The involvement of the circadian system on depression-like behaviors was investigated as well. Analysis of locomotor activity revealed no major differences in daily rhythms that could possibly contribute to the depression-like behaviors. To explore the neural substrates associated with the depression-like behaviors, the brain tissues from these animals were analyzed using immunocytochemistry. Attenuated indices of 5-HT signaling were observed in DLD compared to the BLD group. The results lay the groundwork for establishing a novel animal model and a novel experimental paradigm for SAD. The results also provide insights into the neural mechanisms underlying light-dependent mood changes.

[Diagnostic features, epidemiology, and pathophysiology of seasonal affective disorder]

Seasonal Affective Disorder (SAD) is characterized by patterns of major depressive episodes that occur and remit with the change of seasons. Two seasonal patterns have been identified: summer-type depression with typical depressive signs and symptoms, and winter-type depression with atypical features of depression. In the subsyndromal form of SAD (S-SAD) symptoms are milder, although vegetative symptoms are clinically significant. SAD needs to be differentiated from atypical depression, cyclothymic disorder, and dysthymia or chronic MDD which may be characterized by a winter worsening of symptoms. Full remission of symptoms must occur after the passing of the season for the disorder to merit the diagnosis of SAD. The mean prevalence of SAD in the temperate zone is 3 to 10%, while that of S-SAD is 6 to 20%. In Hungarian general population the occurrence of SAD is 4.6%, and S-SAD is 7.2%. The pathophysiology of SAD seems to be heterogeneous, studies suggest abnormal circadian rhythm and neurotransmitter function (phase shift hypothesis, role of serotonin, dopamin and norepinephrine). Genetic studies focusing on candidate genes involve 5-HTR2A, 5-HTR2C, DRD4, G protein, and clock-related genes.

[Association of obesity and depression]

It has been long known that the frequency of overweight and obese people is higher among depressed and bipolar patients than in the general population. The marked alteration of body weight (and appetite) is one of the most frequent of the 9 symptoms of major depressive episode, and these symptoms occur during recurrent episodes of depression with a remarkably high consequence. According to studies with representative adult population samples, in case of obesity (BMI over 30) unipolar or bipolar depression is significantly more frequently (20-45%) observable. Since in case of depressed patients appetite and body weight reduction is observable during the acute phase, the more frequent obesity in case of depressed patients is related (primarily) not only to depressive episodes, but rather to lifestyle factors, to diabetes mellitus also more frequently occurring in depressed patients, to comorbid bulimia, and probably to genetic-biological factors (as well as to pharmacotherapy in case of medicated patients). At the same time, according to certain studies, circadian symptoms of depression give rise to such metabolic processes in the body which eventually lead to obesity and insulin resistance. According to studies in unipolar and bipolar patients, 57-68% of patients is overweight or obese, and the rate of metabolic syndrome was found to be between 25-49% in bipolar patients. The rate of metabolic syndrome is further increased by pharmacotherapy. Low total and HDL cholesterol level increases the risk for depression and suicide and recent studies suggest that omega-3-fatty acids possess antidepressive efficacy. Certain lifestyle factors relevant to healthy metabolism (calorie reduction in food intake, regular exercise) may be protective factors related to depression as well. The depression- and possibly suicide-provoking effect of sibutramine and rimonabant used in the pharmacotherapy of obesity is one of the greatest recent challenges for professionals and patients alike.

Seasonality of psychopathology and circannual melatonin rhythm

The association of seasonal changes in health and disease has been known for centuries. The prevalence of psychopathological symptoms with seasonal fluctuations and the use of melatonin as a biological marker of circadian and circannual rhythms is well documented. The aim of this work was to study the variability of melatonin secretion between summer and winter in our geographical area (28 degrees N, 16 degrees W) and relate the changes to the level of psychopathology. Ten drug-free, nonsmoker, healthy subjects were studied in summer (August) and winter (December). Blood samples for melatonin assays were collected every hour at night for 5 hr, from 22:00 to 02:00 hr, and next day at noon. Melatonin was assayed by an ELISA technique. Psychopathology was evaluated by means of the 28-item version of the General Health Questionnaire (GHQ-28). All subjects had a circadian rhythm of melatonin secretion in summer and winter. There was a seasonal rhythm with melatonin levels being significantly higher at night in winter than in summer. Melatonin levels at 22:00, 23:00, 24:00 and 01:00 hr and mean melatonin area under the curve (AUC) were significantly higher in winter than in summer. Melatonin AUC increased 80% in winter compared with summer. The GHQ-28 somatic and anxiety subscales and the total GHQ-28 score were significantly higher in winter than summer. Psychopathology scores were significantly and negatively correlated with melatonin production in summer and winter. Our data strongly suggest that melatonin production and psychopathology levels present seasonal fluctuations and these variations should be taken into account when conducting research in this field.

The circadian basis of winter depression

The following test of the circadian phase-shift hypothesis for patients with winter depression (seasonal affective disorder, or SAD) uses low-dose melatonin administration in the morning or afternoon/evening to induce phase delays or phase advances, respectively, without causing sleepiness. Correlations between depression ratings and circadian phase revealed a therapeutic window for optimal alignment of circadian rhythms that also appears to be useful for phase-typing SAD patients for the purpose of administering treatment at the correct time. These analyses also provide estimates of the circadian component of SAD that may apply to the antidepressant mechanism of action of appropriately timed bright light exposure, the treatment of choice. SAD may be the first psychiatric disorder in which a physiological marker correlates with symptom severity before, and in the course of, treatment in the same patients. The findings support the phase-shift hypothesis for SAD, as well as suggest a way to assess the circadian component of other psychiatric, sleep, and chronobiologic disorders.

Circadian phase shifting, alerting, and antidepressant effects of bright light treatment

Bright light treatment is the most potent melatonin suppressor and circadian phase shifter and is a safe nonpharmacologic antidepressant for seasonal depression. In addition, bright light treatment may restore performance in conditions of sleep debt and misalignment between peak performance and the athletic event. This article discusses the therapeutic use of bright light treatment, its side effects, and mechanisms of action.

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.

Bilirubin and the risk of common non-hepatic diseases

Bilirubin is a potent antioxidant but can be toxic at high concentrations. This article critically reviews the reported relationships of plasma bilirubin levels to the severity and/or incidence of various common non-hepatic diseases. Plasma bilirubin levels are reportedly negatively related to the risk of atherosclerotic diseases, cancers, demyelinating neuropathies and seasonal affective disorder. By contrast, the incidence and severity of schizophrenia are increased by elevated bilirubin levels. The data strongly suggest that the level of plasma bilirubin should be considered as a risk factor for several common non-hepatic diseases. Additional studies are needed to clarify the mechanisms of this influence, which are thought to be related to unconjugated bilirubin counteracting the oxidative stress underlying these disorders.

Electroretinography in patients with winter seasonal affective disorder

A retinal sensitivity abnormality has been hypothesized in seasonal affective disorder (SAD). To explore this hypothesis, the electroretinogram (ERG) was used to assess retinal sensitivity at the level of the rod photoreceptor system. We examined 27 depressed patients who met DSM-III-R criteria for major depression, recurrent, with a seasonal (winter) pattern and 23 normal control subjects who were age-paired and sex-matched as much as possible with the SAD patients. ERG testing was performed in dark-adapted, dilated eyes in winter between 10:00 and 15:00 h. Retinal sensitivity was based on the light stimulus intensity necessary to reach a 50-microV amplitude threshold. We found that retinal sensitivity was significantly lower (0.21 log units) in SAD patients compared with normal control subjects and that 55% of the patients had a retinal sensitivity value one standard deviation lower than the mean value of the control subjects. These results are consistent with a retinal hyposensitivity hypothesis for SAD, but the explanation for lower rod photoreceptor sensitivity in SAD is not known. We hypothesize that brain neurotransmitter dysregulation may be at the origin of both the mood disorder and retinal sensitivity change.

The serotonin transporter promoter repeat length polymorphism, seasonal affective disorder and seasonality

BACKGROUND

Conflicting results have been reported in previous association studies of the serotonin transporter promoter repeat length polymorphism (5-HTTLPR), seasonal affective disorder (SAD) and seasonality (seasonal variations in mood and behaviour). The aim of this study was to test for association in new case-control and population-based materials, and to perform a combined analysis of all published studies of 5-HTTLPR and SAD.

METHOD

One hundred and forty-seven new SAD cases and 115 controls were genotyped for 5-HTTLPR and in total 464 patients and 414 controls were included in the pooled analysis. In addition, 226 individuals selected for unusually high or low seasonality scores from a population based material and 46 patients with non-seasonal depression were analysed. Different genetic models were tested and seasonality was analysed both as a qualitative (high v. low) and as a quantitative trait in the different sample sets.

RESULTS

No association between 5-HTTLPR and SAD was found in the new case-control material, in the combined analysis of all samples, or when only including 316 patients with controls (N = 298) selected for low seasonality. A difference was detected between the population based high and low seasonality groups, when assuming a recessive effect of the short allele (20% and 10% short allele homozygotes, respectively, OR (95% CI): 2.24 (1.03-4.91)). Quantitative analysis of seasonality revealed no association with 5-HTTLPR in any sample set.

CONCLUSIONS

These results do not suggest a major role of the short variant of 5-HTTLPR in susceptibility to SAD, but provide modest evidence for an effect on seasonality.

Side effects after phototherapy implementation in addition to fluoxetine or sertraline treatment: a report of two cases

Serotonergic-type side effects (like diarrhoea, hyperthermia, nausea, confusion) were seen after phototherapy in patients receiving fluoxetine or sertraline. Phototherapy was discontinued and symptoms completely resolved. In the authors' opinion, the symptoms were likely to be associated with specific interaction (serotonin effect potentialisation). To the authors' knowledge this is the first report concerning such an effect.

Rate of oxygen consumption in seasonal and non-seasonal depression

Most depressives suffer from weight loss, anorexia and insomnia, while for winter depressives the typical symptoms are weight gain, carbohydrate craving, overeating, oversleeping and extreme lack of energy. It is important to know whether winter depressives differ from most other depressives on measures of energy regulation. In wintertime, we evaluated the rate of oxygen consumption in relationship to neuro-vegetative depressive symptoms in 92 Siberian women. The seated subjects underwent oxyspirography in the mid-morning (1.5 hours after a standard breakfast). It was found that the oxygen consumption rate was similar in non-depressed women (n = 25) and depressed women with non-seasonal depression (n = 27). The comparatively lower values were obtained in women with winter depression (n = 40). This finding supports the suggestion that the behaviour disturbances typical for winter depression may represent a physiological feedback loop to energy conservation.

Monoaminergic function in the pathogenesis of seasonal affective disorder

Seasonal affective disorder/winter type (SAD) is characterized by recurrent depressive episodes during autumn and winter alternating with non-depressive episodes during spring and summer. Light therapy with full-spectrum, bright white light has been shown to be effective for this condition. Several hypotheses have been discussed in the literature about the pathogenesis of SAD. The most prominent includes disturbances in central monoaminergic transmission. Evidence can be inferred from studies showing a seasonal rhythm of central and peripheral serotonergic functioning which may be a predisposing factor for SAD. Some of the symptoms of SAD are believed to represent an attempt to overcome a putative deficit in brain serotonergic transmission. Moreover, 5-HT receptor challenge studies suggest altered activity at or downstream to central 5-HT receptors. Monoamine depletion studies support hypotheses about serotonergic and catecholaminergic dysfunctions in SAD and suggest that light therapy may well compensate for this underlying deficit. Further, albeit indirect, support for the importance of monoaminergic mechanisms in SAD and its involvement in the mechanism of the action of light therapy comes from studies showing antidepressant efficacy of serotonergic and noradrenergic antidepressants in the treatment of SAD. Altogether, disturbances in brain monoaminergic transmission seem to play a key role in the pathogenesis of SAD; monoaminergic systems may also play an important role in the mechanisms of the action of light therapy.

Melatonin secretion in SAD patients and healthy subjects matched with respect to age and sex

Among the competing hypotheses concerning the aetiology of SAD is the melatonin hypothesis, which is the target of this study. 5 test subjects with SPAQ seasonality score (SS) > or = 9 and 5 controls with SS 3/4 4 participated in the study. The participants took saliva samples at home. Samples were collected 4 times a day for 3 days in March, 1999. Melatonin concentrations were determined by RIA. No significant differences in circadian rhythms were found between the groups; i.e. the curves for both groups ran parallel. However the concentrations of melatonin in the SAD patients were found to be on average 2.4 times as high as in the control group; the difference is significant at p<0.001. Our results support the melatonin hypothesis.

Dopamine transporter availability in symptomatic depressed patients with seasonal affective disorder and healthy controls

BACKGROUND

During recent years hypotheses about the pathophysiology of seasonal affective disorder/winter type (SAD) have focused monoaminergic mechanisms. There is substantial evidence that serotonergic systems play an important role. The potential role of catecholaminergic pathways has not been fully explored.

METHODS

Eleven drug-free, symptomatic depressed patients with SAD and 11 healthy age- and gender-matched healthy controls were invited to participate in a 123Ibeta-CIT single photon emission computed tomography (SPECT) study to assess striatal density of dopamine transporters (DATs). The cerebellum was used as reference region. Ratios were calculated between mean counts in left and right striatum and cerebellum. These ratios minus I represent specific/non-displaceable binding and are assumed to be directly related to DAT availability at the time of binding equilibrium.

RESULTS

Displaceable 153Ibeta-CIT binding in the area corresponding to the left striatum was significantly reduced in SAD patients compared to healthy controls (10.49+/-0.91 v. 1195+/-1.54, respectively; 2-tailed P = 0.017, Mann-Whitney U test).

CONCLUSIONS

These data suggest reductions in the availability of striatal DAT binding sites in untreated symptomatic depressed SAD patients. It remains unclear whether these reductions represent a primary defect or an attempt to overcome a state of possible lowered dopamine availability in the synaptic cleft during a depressive episode of SAD. However, these findings provide evidence that brain dopaminergic systems may be involved in the pathophysiology of SAD.

Extraocular light therapy in winter depression: a double-blind placebo-controlled study

BACKGROUND

It has been hypothesized that the circadian pacemaker is phase delayed in seasonal affective disorder, (SAD) winter type, and that the phase advance resulting from morning ocular light accounts for the efficacy of light therapy. Extraocular light has been reported to produce phase-shifts of the human circadian pacemaker. This allows a double-blind, placebo-controlled study of light therapy in SAD.

METHODS

Twenty-nine SAD patients participated. Clinical state was measured on days 1, 8, and 15 of the protocol. From days 4 through 8, 15 patients (4 M, 11 F) received extraocular light by fiberoptic illumination, and 14 (4 M, 10 F) placebo (no light) in the popliteal fossae, from 8 AM to 11 AM. In the evenings of days 3 and 8, the salivary dim light melatonin onset (DLMO) was assessed. Patients completed daily self-ratings on mood, alertness, and sleep.

RESULTS

Both conditions showed a progressive improvement of clinical state over time. Between conditions, no significant differences were observed in clinical scores, the self-ratings on mood and alertness, and in timing of the DLMO before and directly after treatment.

CONCLUSIONS

The response to extraocular light therapy in SAD patients did not exceed its placebo effect. Extraocular light did not induce a phase shift of the circadian pacemaker.

Seasonal affective disorder and serotonin-related polymorphisms

Disturbances in central serotonergic systems have been hypothesized to be involved in seasonal affective disorder (SAD). Association between SAD and the shorter allele of the serotonin transporter promoter repeat length polymorphism (5-HTTLPR) has been reported in an American sample. We have genotyped 82 SAD patients and 82 healthy controls from Sweden, Finland, and Germany for this and five other polymorphisms in the genes coding for serotonin receptors 5-HT2A and 5-HT2C, tryptophan hydroxylase and white. No associations with SAD or seasonality (seasonal variations in mood and behavior) were detected. Although minor effects cannot be excluded, our results suggest that these polymorphisms do not play a major role in the pathogenesis of SAD in the northern European population.

Stimulation of reactive oxygen species production by an antidepressant visible light source

BACKGROUND

The mechanism by which visible light stimulates chronobiological phase-shifting or antidepressant effects in humans is unknown.

METHODS

Normal human NIH/3T3 nonpigmented fibroblasts were irradiated with a visible light source (SunRay) used in the treatment of winter seasonal depression. Electron spin resonance was assessed before and after 10 min of illumination at 2 mW/cm(2) (illuminance of 3700 lux), with and without the presence of 5 microL of 0.0214 mg/mL vitamin C.

RESULTS

The fibroblasts showed evidence of production of reactive oxygen species after 10 min of irradiation.

CONCLUSIONS

These in vitro data establish that an antidepressant source of visible light is capable of inducing the production of reactive oxygen species in skin. Such species may participate in signal transduction pathways leading to mood changes.

Genetic studies of seasonal affective disorder and seasonality

Genetic studies of seasonal affective disorder (SAD) and seasonality have received considerable attention over the past several years. Studies of the prevalence of SAD and nonseasonal mood disorders among relatives of patients with SAD suggested a familial contribution to the development of SAD. Two twin studies demonstrated a substantial role of genetic variation in seasonality. Two genetic variants related to serotonergic transmission, the 5-HTTLPR and the 5-HT(2A)-1438G/A gene promoter polymorphisms, have been found to be associated with SAD. 5-HTTLPR is also associated with seasonality in SAD patients and in the general population. It is not clear whether SAD is inherited as a distinct entity or whether seasonality and depression are separate heritable traits that happen to coincide in certain individuals. Vulnerability to SAD and disease pathology may be influenced by many genes, perhaps on several chromosomes.

Monoamine depletion in non-pharmacological treatments for depression

Non-pharmacological treatments such as light therapy for seasonal affective disorder or sleep deprivation for non-seasonal depression have been shown to treat depression effectively. With the use of the tryptophan depletion paradigm and the catecholamine depletion paradigm we assessed the role of brain serotonergic and catecholaminergic systems respectively. We found that disturbances in brain serotonin systems play a key role in the pathogenesis of seasonal affective disorder and that light therapy may compensate for the underlying deficit. Moreover there is evidence that catecholaminergic systems may be involved in the mechanism of action of light therapy. Tryptophan depletion studies suggest that sleep deprivation does not exert its antidepressant effects by involving brain serotonin systems alone. Interestingly, tryptophan depletion prevented the relapse after the recovery night, possibly by enhancing brain serotonin transmission after the depletion procedure.

Mood and energy regulation in seasonal and non-seasonal depression before and after midday treatment with physical exercise or bright light

The effects of two non-drug treatments (physical exercise and bright light) on mood, body weight and oxygen consumption were compared in age-matched groups of female subjects with winter depression, non-seasonal depression or without depression. It was found that oxygen consumption in the pre-treatment condition was similar in non-depressed subjects (n=18) and depressed non-seasonals (n=18), while comparatively lower values were obtained in winter depression (n=27). Neither mood nor metabolic parameters changed significantly in the group of nine untreated winter depressives. One week of physical exercise (1-h pedaling on a bicycle ergometer between 13.00 and 14.00 h) increased oxygen consumption in the group of nine winter depressives and lowered oxygen consumption in nine-subject groups of depressed and non-depressed non-seasonals. One week of bright light treatment (2-h exposure to 2500 lux between 14.00 and 16.00 h) increased oxygen consumption in nine winter depressives and nine non-depressed subjects, while no significant change in oxygen consumption was found in nine subjects with non-seasonal depression. Weight loss was observed in the groups treated with physical exercise and in the group of light-treated winter depressives. Winter depression responded equally well to exercising and light, while a significant therapeutic difference in favor of exercising was found in non-seasonal depression. Overall, the results of the study suggest that energy-regulating systems are implicated in the antidepressant action of the non-drug treatments.

[123I]-beta-CIT SPECT imaging shows reduced brain serotonin transporter availability in drug-free depressed patients with seasonal affective disorder

BACKGROUND

Numerous findings indicate alterations in brain serotonin systems in seasonal affective disorder (SAD). [(123)I]-2-beta-carbomethoxy-3-beta-(4-iodophenyl)-tropane ([(123)I]-beta-CIT) labels serotonin transporters (5-HTTs) in the midbrain. We performed a [(123)I]-beta-CIT single photon emission computer tomography (SPECT) study under the hypothesis of lower [(123)I]-beta-CIT binding reflecting reduced central 5-HTT availability in depressed SAD patients.

METHODS

Depressed SAD patients and healthy control subjects were investigated using [(123)I]-beta-CIT SPECT 4 hours and again 24 hours after tracer injection. Subjects had either never used psychotropic medication or had been drug-free for at least 6 months prior to the investigation. Specific-to-nondisplaceable partition coefficient (V(3)") was calculated for the thalamus-hypothalamus and the midbrain-pons; the cerebellum served as a reference region.

RESULTS

Patients showed a reduction in V(3)" in thalamus-hypothalamus (2.41+/-0.3 vs. 2.84+/-0.4; p = .026) 24 hours post tracer injection (p.i.). No difference between patients and control subjects was found in midbrain-pons (1.31+/-0.2 vs. 1.42+/-0.2; p = .39). No differences were detected in the SPECT acquisitions 4 hours p.i.

CONCLUSIONS

Depressed SAD patients showed lower specific-to-nondisplaceable [(123)I]-beta-CIT binding in the region of interest (ROI) thalamus-hypothalamus. The small size of the midbrain-pons ROI may have contributed to the failure to show a difference in this ROI as well. Similar to reduced midbrain 5-HTT availability in nonseasonal depression, depression in SAD seems to be associated with reduced 5-HTT availability to the thalamus-hypothalamus.

Extrapineal melatonin and exogenous serotonin in seasonal affective disorder

Visible light inhibits the binding of melatonin and serotonin to cultured human peripheral blood mononuclear leukocytes (PBMLs) in winter. The decreased binding switches the metabolism in PBMLs towards serotonin synthesis, resulting in the reduced production of melatonin. The ingestion of L-tryptophan during the day is hypothesized to increase the levels of melatonin, released from the gastrointestinal tract, in patients with winter seasonal affective disorder (SAD). Due to the relative shortage of light, coincident with a predisposed metabolic error, there would be no switch towards serotonin synthesis among winter SAD patients in winter. The rate of serotonin synthesis could thus remain inadequately low to maintain optimal mood in winter SAD patients.

[Melatonin and seasonal depression]

Melatonin (MEL) hypothesis in seasonal affective disorders (SAD) is supported by: a) historical hint; b) circadian and seasonal MEL periodicity with evidence that the SAD is related to photoperiod; c) relationship between incidence and severity of SAD and latitude; d) the response to bright artificial light (ineffective in depression) which mimics summer time; e) MEL administration can induce some symptoms of the SAD; f) several antidepressant drugs increase MEL plasma levels. Several of these findings are disproved: the light acts independently from the MEL, some antidepressant agents act without modifying MEL levels; a consistent alteration in MEL secretion within SAD has not been convincingly demonstrated. Relationship between incidence and severity of SAD and latitude suggests a new potential implication of MEL in SAD. The daytime melatonin values reflect changes along the scale of a year in sunshine. Accordingly, the about-yearly periodicity, much larger in amplitude than the half-yearly component, yields ratios smaller than unity. By contrast during darkness an about-half-yearly component is more prominent. As the aurora zone is approached, the intensity of magnetic disturbances increases. Thus, the intensity of these two variables shows inverse relationships with latitude and geomagnetic field decreases plasma levels of MEL and inhibits MEL function.

Suppression of melatonin secretion by bright light in seasonal affective disorder

Eleven patients with winter seasonal affective disorder and 10 healthy controls were exposed to light of 3300 lux for 5 min and for 1 hour respectively on consecutive evenings at 22:00 hours during winter and summer. In the winter, the measurements were undertaken both before and after the treatment with bright light for 2 weeks. In the summer, there was no treatment. Melatonin concentration in saliva and subjective sleepiness were measured at 22:00 and 23:00 hours on each test. There was no significant difference in the suppression of melatonin in response to the light tests between the patients and the controls. Exposure to light reduced the level of subjective sleepiness more among the patients compared to the control subjects. This reduction was not associated with the change in melatonin secretion nor the improvement in depressive symptoms.

Two naturally occurring amino acid substitutions of the 5-HT2A receptor: similar prevalence in patients with seasonal affective disorder and controls

We screened the 5-HT2A receptor gene coding region in 50 patients with seasonal affective disorder (SAD) using a single strand conformational polymorphism analysis and estimated the frequencies of two synonymous and two non-synonymous substitutions we detected in 70 Centre d'Etude du Polymorphism Humain (CEPH) population controls and 62 normal controls. Both of the amino acid substitutions: Ala447-Val447 and His452-Tyr452, were located within the cytoplasmic. C-terminal tail of the receptor. Rarer allele frequencies in CEPH were 0.7% and 9.3% for Val447 and Tyr452, respectively. Allele frequencies of all four polymorphisms, including the two amino acid substitutions, were not significantly different in SAD patients as compared to CEPH and normal controls. Lack of association of Val447 and Tyr452 to SAD is consistent with observations showing normal 5-HT2A receptor Ca2+ response in platelets with this disorder, however, the two 5-HT2A amino acid substitutions may lead to differences in behavioral phenotypes.

1,25 (OH)2 vitamin D3 levels in seasonal affective disorder: effects of light

1,25 (OH)2 vitamin D3 levels were assessed in nine females and six males with winter seasonal affective disorder and in 15 age- and gender-matched controls in winter during periods with and without treatment with light therapy. No difference was found between groups or across conditions, though wide variations within each group make the presence of a type II error possible.

[Winter depression and light therapy]

Winter depression (Seasonal Affective Disorder, SAD) is a depressive illness, which starts in the autumn and disappears in the spring. The depression is, in contrast to the typical endogenous depression, characterized by increased appetite with carbohydrate craving, and increased sleep. There is an increase in the frequency of the illness towards the geographical poles. About 80% of the patients are women. The most remarkable aspect of the depression is however, that it can be effectively treated with bright light, given two hours daily for one to two weeks. A number of biological functions are currently under investigation in relation to winter depressions; among these are the metabolism of melatonin, various diurnal rhythms and the serotonergic system.

Platelet [3H]paroxetine binding, 5-HT-stimulated Ca2+ response, and 5-HT content in winter seasonal affective disorder

The present study was designed to evaluate cellular serotonergic functions in winter seasonal affective disorder (SAD) using serotonin (5-HT)-stimulated Ca2+ response as an integrated measure of 5-HT2 receptor function in platelets, [3H]paroxetine binding to characterize the platelet 5-HT transporter and 5-HT content as an index of the platelet storage capacity for this neurotransmitter amine. Purified density-dependent subpopulations of platelets in untreated and light-treated SAD patients and matched controls were investigated in order to control for possible variations in platelet turnover. We found no differences between SAD patients and controls on any of the measures, nor between light therapy conditions in SAD patients, although we found a higher Bmax of [3H]paroxetine binding and 5-HT content in heavy platelets compared to light platelets. Although the validity of platelet serotonergic measures as a model for brain serotonergic systems still remains to be elucidated, we found no evidence of platelet serotonergic abnormalities in our sample of SAD patients.

Behavioral responses to intravenous meta-chlorophenylpiperazine in patients with seasonal affective disorder and control subjects before and after phototherapy

A comparison of the baseline and post-infusion effects of the serotonin agonist meta-chlorophenylpiperazine (m-CPP) in 10 patients with seasonal affective disorder (SAD) and 11 healthy control subjects revealed significantly different subjective response profiles between the groups. Several baseline and m-CPP-stimulated responses in symptoms putatively related to serotonergic function changed significantly after a week's exposure to phototherapy in the SAD patients but not the control subjects. Before phototherapy, depressed patients with SAD reported activation-euphoria responses to m-CPP and significant decreases in carbohydrate hunger, but insignificant changes in feeling slowed or sleepy, while control subjects reported no mood or appetite changes but significant increases in feeling slowed down following m-CPP. After phototherapy, which led to a significant reduction in baseline depressive symptom rating to near-euthymic levels in the SAD patients, almost all of the patients' responses to m-CPP were normalized and no longer differed from the control subjects' responses. These results provide evidence of a possible dysregulation in serotonergic neurotransmission in depressed SAD patients that normalizes following treatment with phototherapy.

Seasonal affective disorder: lower or raised resting metabolic rate?

Patients with seasonal affective disorder (SAD) were predicted to have low resting metabolic rates (RMR). However, studies have revealed that SAD patients have significantly higher RMR values. Increased melatonin may explain it.

Cerebral glucose metabolism in patients with summer seasonal affective disorder

Positron emission tomography scans of nine patients diagnosed with summer seasonal affective disorder (SSAD) were compared with scans of 45 normal control subjects to investigate differences in brain glucose metabolism. All subjects performed an auditory discrimination task beginning several minutes before injection of F-18-deoxyglucose and continuing for 30 minutes after injection. Regional glucose metabolic rates were extracted from 60 rectangular regions of interest measured in five planes selected as atlas matches from 28 total slices. Statistically significant differences between patients with SSAD and normal control subjects were found in cerebral glucose metabolic rate and also in normalized regional glucose metabolic rates in the orbital frontal cortex and in the left inferior parietal lobule.

A seasonal depression. Management of seasonal affective disorder

1. SAD is a mood disorder characterised by recurring cyclic periods of autumn/winter dysthymia alternating with late spring/summer euthymia or hypomania. 2. It is now thought that SAD sufferers may be deficient in certain brain chemicals, and it is likely that the interactions of a number of neurotransmitters are responsible for the disorder. 3. In the UK, 72% of SAD sufferers report an increase in sleep from around seven hours in the summer to nine in winter. 4. Phototherapy has been proved an effective treatment for SAD, and lamps for phototherapy are becoming increasingly available.

Preliminary data on the metabolic brain pattern of patients with winter seasonal affective disorder

The brain metabolic pattern of patients with winter seasonal affective disorder with and without light treatment was determined by positron emission tomography. Compared with controls, patients with seasonal affective disorder with and without light treatment had globally lower metabolic rates, relatively lower superior medial frontal cortex rates, and somewhat higher basal ganglia rates. Patients receiving light treatment had a relatively higher rate in an occipital region of interest containing the primary visual cortex. Patients without light treatment had relatively higher metabolic rates in right parietal and medial orbitofrontal cortex and lower rates in the left parietal cortex. Patients not receiving light treatment had a hemispheric metabolic asymmetry (left greater than right) for the midprefrontal cortex located 67 mm above the canthomeatal line. The right side of this region, previously found reduced in manic-depressive illness and schizophrenia, was decreased primarily in patients with seasonal affective disorder with fewer atypical depressive symptoms. These "abnormal" prefrontal and parietal cortex regions appeared highly "coupled" in the patients with seasonal affective disorder.