Seasonal variation of serotonin turnover in human cerebrospinal fluid, depressive symptoms and the role of the 5-HTTLPR

Effect of daily temperature variations on years of life lost from suicide in the capital city of South Korea

Suicide is one of the important public health issues among mental health problems. Given that suicide significantly increases the risk of premature death, it is essential to identify potential risk factors for its prevention. It has been known that meteorological variables have an impact on suicide, but the influence of temperature variations on suicide has been undetermined. A generalized additive model utilizing a Gaussian distribution was used to assess the association between diurnal temperature range (DTR) and YLLs from suicide after rigorous adjustment for confounders, including temperature. Moreover, the lag effects of DTR up to 7 days were considered when performing the main analysis and subgroup analyses by sex, age, level of education, occupation, marital status, place of death, suicide method, and season. DTR and YLLs from suicide showed a significant positive association over various lag structures. The best-fitting lag structure was lag 0-6 (7.03 years, 95% confidence intervals: 3.49, 10.58 years). In subgroup analyses, DTR and YLLs from suicide showed the most significant associations in males (3.79 years), those in the age group of 36-64 years (4.22 years), unemployed (5.02 years), unmarried (3.98 years), death inside buildings (5.42 years), violent method (6.66 years), and spring (4.30 years). Our study offers new evidence that DTR may contribute as a risk factor for YLLs from suicide. Our finding can be considered when establishing preventive measures for premature death from suicide.

Increased Suicide Mortality and Reduced Life Expectancy Associated With Ambient Heat Exposure

INTRODUCTION

Ambient heat exposure is a risk factor for suicide in many regions of the world. However, little is known about the extent to which life expectancy has been shortened by heat-related suicide deaths. This study aimed to evaluate the short-term effects of heat on suicide mortality and quantify the reduced life expectancy associated with heat in China.

METHODS

A time-stratified, case-crossover analysis in 2023 was performed during the warm season (May to September) from 2016 to 2020 to assess the short-term association between extreme heat (the 95th percentile of mean temperature) and suicide mortality in Anhui Province, China. A subgroup analysis was performed according to sex, age, marital status, suicide type, and region. The attributable fraction and years of life lost due to heat were calculated, and the heat-related life expectancy loss was estimated.

RESULTS

This study included 9,642 suicide deaths, with an average age of 62.4 years and 58.8% of suicides in males. Suicide risk was associated with an 80.7% increase (95% confidence interval [CI]: 21.4%-68.9%) after exposure to extreme heat (30.6°C) in comparison to daily minimum temperature (7.9°C). Subgroup analysis revealed that heat-related suicide risk was more prominent in the married population than in the unmarried population. Heat was estimated to be associated with 31.7% (95% CI: 18.0%-43.2%) of the suicides, corresponding to 7.0 years of loss in life expectancy for each decedent.

CONCLUSIONS

Heat exposure was associated with an increased risk of suicide and reduced life expectancy. However, further prospective studies are required to confirm this relationship.

Effect of Short Photoperiod on Behavior and Brain Plasticity in Mice Differing in Predisposition to Catalepsy: The Role of BDNF and Serotonin System

Seasonal affective disorder is characterized by depression during fall/winter as a result of shorter daylight. Catalepsy is a syndrome of some grave mental diseases. Both the neurotransmitter serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) are involved in the pathophysiological mechanisms underlying catalepsy and depressive disorders. The aim was to compare the response of behavior and brain plasticity to photoperiod alterations in catalepsy-resistant C57BL/6J and catalepsy-prone CBA/Lac male mice. Mice of both strains were exposed for six weeks to standard-day (14 h light/10 h darkness) or short-day (4 h light/20 h darkness) conditions. Short photoperiod increased depressive-like behavior in both strains. Only treated CBA/Lac mice demonstrated increased cataleptic immobility, decreased brain 5-HT level, and the expression of Tph2 gene encoding the key enzyme for 5-HT biosynthesis. Mice of both strains maintained under short-day conditions, compared to those under standard-day conditions, showed a region-specific decrease in the brain transcription of the Htr1a, Htr4, and Htr7 genes. After a short photoperiod exposure, the mRNA levels of the BDNF-related genes were reduced in CBA/Lac mice and were increased in the C57BL/6J mice. Thus, the predisposition to catalepsy considerably influences the photoperiodic changes in neuroplasticity, wherein both C57BL/6J and CBA/Lac mice can serve as a powerful tool for investigating the link between seasons and mood.

Self-harm and interpersonal violence due to high temperature from the global burden of disease study 2019: A 30-year assessment

BACKGROUND

The impact of global warming on health due to climate change is increasingly studied, but the global burden of self-harm and interpersonal violence attributable to high temperature is still limited. This study aimed to systematically assess the burden of self-harm and interpersonal violence attributable to high temperature globally or by region and climate zone from 1990 to 2019.

METHODS

We obtained the global, regional, and national deaths, disability-adjusted life years (DALYs), age-standardized mortality rates (ASMR), and age-standardized disability-adjusted life year rates (ASDR) of self-harm and interpersonal violence due to high temperature from 1990 to 2019 through the Global Burden of Disease Study (GBD) 2019. The burden of self-harm and interpersonal violence due to high temperature was estimated by age, sex, climate zone, the socio-demographic index (SDI), and the healthcare access and quality index (HAQ). Average annual percentage changes (AAPCs) in ASMR and ASDR were calculated for 1990-2019 using the Joinpoint model.

RESULTS

From 1990 to 2019, the global deaths and DALYs related to self-harm and interpersonal violence due to high temperature increased from 20,002 (95% UI, 9243 to 41,928) and 1,107,216 (95% UI, 512,062 to 2,319,477) to 26,459 (95% UI, 13,574 to 47,265) and 1,382,487 (95% UI, 722,060 to 2,474,441), respectively. However, the ASMR and ASDR showed varying degrees of decreasing trends, with decreases of 13.36% and 12.66%, respectively. The ASMR was high and declining in low and low-middle SDI regions, particularly in tropical and subtropical regions. In addition, SDI and HAQ index were negatively correlated with ASMR in 204 countries and regions.

CONCLUSIONS

The global burden of self-harm and interpersonal violence attributed to high temperature has decreased over the past 30 years, but the number of deaths and DALYs continues to rise. Climate change continues to make heat stress a significant risk factor for self-harm and interpersonal violence worldwide.

Relationship between Depressive Symptoms and Weather Conditions

Background: Weather is a well-known factor worldwide in psychiatric problems such as depression, with the elderly and females being particularly susceptible. The aim of this study was to detect associations between the risk of depressive symptoms (DS) and weather variables. Methods: 6937 participants were assessed in the baseline survey of the Health Alcohol Psychosocial Factors in Eastern Europe (HAPIEE) study during 2006−2008. To assess the risk of DS, a multivariate logistic model was created with predictors such as socio-demographic factors, health behaviors, and weather variables. Results: DS were found in 23.4% of the respondents, in 15.6% of males and in 29.9% in females. A higher risk of DS (by 25%) was associated with November−December, a rising wind speed, and relative humidity (RH) < 94% and snowfall during the cold period occurring 2 days before the survey. A higher air temperature (>14.2 °C) predominant during May−September had a protective impact. A higher risk of DS in males was associated with lower atmospheric pressure (<1009 hPa) 2 days before. Females were more sensitive to the monthly variation, snowfall, and RH. Conclusions: The findings of our study suggest that some levels of weather variables have a statistically significant effect on DS.

Ambient Temperature and External Causes of Death in Japan from 1979 to 2015: A Time-Stratified Case-Crossover Analysis

BACKGROUND

Although substantial evidence suggests that high and low temperatures are adversely associated with nonaccidental mortality, few studies have focused on exploring the risks of temperature on external causes of death.

OBJECTIVES

We investigated the short-term associations between temperature and external causes of death and four specific categories (suicide, transport, falls, and drowning) in 47 prefectures of Japan from 1979 to 2015.

METHODS

We conducted a two-stage meta-regression analysis. First, we performed time-stratified case-crossover analyses with a distributed lag nonlinear model to examine the association between temperature and mortality due to external causes for each prefecture. We then used a multivariate meta-regression model to combine the association estimates across all prefectures in Japan. In addition, we performed stratified analyses for the associations by sex and age.

RESULTS

A total of 2,416,707 external causes of death were included in the study. We found a J-shaped exposure-response curve for all external causes of death, in which the risks increased for mild cold temperatures [20th percentile; relative risk (RR)=1.09 (95% confidence interval [CI]: 1.05,1.12)] and extreme heat [99th percentile; RR=1.24 (95% CI: 1.20, 1.29)] compared with those for minimum mortality temperature (MMT). However, the shapes of the exposure-response curves varied according to four subcategories. The risks of suicide and transport monotonically increased as temperature increased, with RRs of 1.35 (95% CI: 1.26, 1.45) and 1.60 (95% CI: 1.35, 1.90), respectively, for heat, whereas J- and U-shaped curves were observed for falls and drowning, with RRs of 1.14 (95% CI: 1.03, 1.26) and 1.95 (95% CI: 1.70, 2.23) for heat and 1.13 (95% CI: 1.02, 1.26) and 2.33 (95% CI: 1.89, 2.88) for cold, respectively, compared with those for cause-specific MMTs. The sex- and age-specific associations varied considerably depending on the specific causes.

DISCUSSION

Both low and high temperatures may be important drivers of increased risk of external causes of death. We suggest that preventive measures against external causes of death should be considered in adaptation policies. https://doi.org/10.1289/EHP9943.

The effect of meteorological variables on suicide

We aimed to reveal the relationship between the meteorological variables and suicide rates (completed suicides and suicide attempts) independently of the seasonal cycle and holiday effects. This is an observational retrospective study. We collected the data on age, gender, and suicide method of all suicide cases transferred to hospitals from the scene by emergency medical services as well as those cases in which the victim died on the scene between January 1, 2017 and June 30, 2019. We also collected data on maximum, minimum, and average temperatures (°C), average humidity (%), and average actual pressure (hPa) measured daily in Ankara. The total number of cases due to suicide between the given dates was 6777. The suicide method in 60.1% of the cases was drug poisoning, which was the most common suicide method. Investigating the effect of meteorological variables on suicide cases (suicide attempts and completed suicides), the present study found that after smoothing the effect of the day of the week and seasonality, an increase in the minimum temperature on the day of the application by 1 unit (1°C degree) leads to an increase in the number of suicides by 0.01 point (0.01 ± 0.005, p = 0.046). There was no significant change in the variables other than the minimum temperature. We believe that the results of the present study will contribute to growing body literature about the epidemiology of suicide. We also believe that there is a need for large-scale studies that include individual data to reveal causality.

Vitamin D and N-Acetyl Cysteine Supplementation in Treatment-Resistant Depressive Disorder Patients: A General Review

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Major Depressive Disorder (MDD) is often a lifetime disabling mental illness as individuals with MDD might not benefit from standard-therapy, including both pharmacological and psychosocial interventions. Novel therapies are, therefore, required.

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It was shown by recent preclinical and clinical studies that the dysfunction of glutamatergic neurotransmission might be involved in the pathophysiology of MDD. Furthermore, neuroimmune alterations could have a significant role in the pathogenesis of MDD.

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Vitamin D is a neurosteroid hormone essential for several metabolic processes, immune responses, and for regulating neurotrophic-neuroprotective processes, neurotransmission and synaptic plasticity. Recent studies have also shown Vitamin D deficiency in patients with severe psychiatric disorders, including MDD.

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Lately, clinical studies have shown the neuroprotective action of N-acetyl cysteine (NAC) through the modulation of inflammatory pathways and via the modulation of synaptic release of glutamate in cortico-subcortical brain regions; the cysteine-glutamate antiporter.

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This paper reviews the therapeutic use of Vitamin D and NAC and among individuals with refractory MDD to the first- line pharmacological interventions, reviewing the clinical studies published in the last decade.

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A detailed summary of the current evidence in this area aims to better inform psychiatrists and general practitioners on the potential benefits of Vitamin D and NAC supplementation for this disorder.

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Nutraceutical supplementation with Vitamin D and NAC in treatment-resistant MDD patients may be important not only for improving depressive clinical manifestations but also for their safety and tolerability profile. This is of great interest, especially considering the need for treating special populations affected by MDD, such as youngsters and elders. Finally, the nutraceutical approach represents a good choice, considering its better compliance by the patients compared to traditional psychopharmacological treatment.

The impact of extreme heat and heat waves on emergency ambulance dispatches due to external cause in Shenzhen, China

BACKGROUND

Compared to hospital admissions (HAs), emergency ambulance dispatches (EADs) can be considered a real-time outcome for evaluating the public health impacts of ambient temperature.

OBJECTIVES

This study aimed to assess if temperature has a causal effect on cause-specific EADs and its potential main and added effect in Shenzhen from 2013 to 2017.

METHODS

A distributed lag nonlinear model (DLNM) with quasi-Poisson distribution was applied to quantify the association between temperature and EADs. Likewise, the fraction of EADs attributable to different temperature ranges was calculated to identify extreme temperature ranges affecting population health. We then explored the main and added wave effects of heatwaves.

RESULTS

Ambient temperature showed a U-shaped association with EADs. The minimum risk temperature was 17 °C (16th percentile of the daily mean temperature). Compared with the cold, the relative risk (RR) of heat on EADs presented smaller but the attributable risk larger. The main effects of heatwaves on EADs varied with external causes; and the peak RR of heat on EADs was observed in suicidal behaviors with heatwaves defined as 3 or more days with temperatures above the 75th percentile (RR = 4.53, 95% CI: 1.23-16.68), followed by assault (RR = 2.36, 95% CI: 1.25-4.48) and accidents (RR = 1.72, 95% CI: 1.30-2.28), while the added wave effect was negligible.

CONCLUSIONS

Heat was responsible for a higher proportion of EADs than cold. Most of the increase in health risk during warm season can be simply ascribed to the independent effects of daily temperature occurrences whether it is or not on the heat-wave day. And the main effects of heatwaves on cause-specific EADs showed varied change trends, of which the incidence of suicides seems more susceptible, followed by assault and accidents.

Light as a modulator of emotion and cognition: Lessons learned from studying a diurnal rodent

Light profoundly affects the behavior and physiology of almost all animals, including humans. One such effect in humans is that the level of illumination during the day positively contributes to affective well-being and cognitive function. However, the neural mechanisms underlying the effects of daytime light intensity on affect and cognition are poorly understood. One barrier for progress in this area is that almost all laboratory animal models studied are nocturnal. There are substantial differences in how light affects nocturnal and diurnal species, e.g., light induces sleep in nocturnal mammals but wakefulness in diurnal ones, like humans. Therefore, the mechanisms through which light modulates affect and cognition must differ between the chronotypes. To further understand the neural pathways mediating how ambient light modulates affect and cognition, our recent work has developed a diurnal rodent model, the Nile grass rat (Arvicanthis niloticus), in which daytime light intensity is chronically manipulated in grass rats housed under the same 12:12 hour light/dark cycle. This simulates lighting conditions during summer-like bright sunny days vs. winter-like dim cloudy days. Our work has revealed that chronic dim daylight intensity results in higher depression- and anxiety-like behaviors, as well as impaired spatial learning and memory. Furthermore, we have found that hypothalamic orexin is a mediator of these effects. A better understanding of how changes in daytime light intensity impinge upon the neural substrates involved in affect and cognition will lead to novel preventive and therapeutic strategies for seasonal affective disorder, as well as for non-seasonal emotional or cognitive impairments associated with light deficiency.

Effect of vitamin D supplementation on depressive symptoms and psychological wellbeing in healthy adult women: a double-blind randomised controlled clinical trial

Epidemiological evidence has linked low vitamin D status to a range of mood disorders. However, studies examining whether vitamin D supplementation can improve mood-related outcomes in healthy populations are limited. We investigated whether vitamin D supplementation over winter is beneficial for improving mood-related outcomes in healthy women. A total of 152 healthy women (18–40 years) in Dunedin, New Zealand were randomly assigned to receive 50 000 IU (1·25 mg) of oral vitamin D₃ or placebo once per month for 6 months. They completed the Center for Epidemiologic Studies Depression Scale, the anxiety subscale of the Hospital Anxiety and Depression Scale and the Flourishing Scale every month. Additionally, they reported their positive and negative mood each day for three consecutive days every 2 months. Participants provided a blood sample at the beginning and at the end of the study for 25-hydroxyvitamin D₃ analysis. ANCOVA was used to compare the outcome measures between the groups, controlling for baseline. We found no evidence of lower depression (P = 0·339), lower anxiety (P = 0·862), higher flourishing (P = 0·453), higher positive moods (P = 0·518) or lower negative moods (P = 0·538) in the treatment group compared with the control group at follow-up. Mood outcomes over the study period were similar for the two groups. We found no evidence of any beneficial effect of monthly vitamin D₃ supplementation on mood-related outcomes in healthy premenopausal women over the winter period, so recommendations for supplementations are not warranted in this population for mood-related outcomes.

Positive and balancing selection on SLC18A1 gene associated with psychiatric disorders and human-unique personality traits

Maintenance of genetic variants susceptible to psychiatric disorders is one of the intriguing evolutionary enigmas. The present study detects three psychiatric disorder‐relevant genes (CLSTN2, FAT1, and SLC18A1) that have been under positive selection during the human evolution. In particular, SLC18A1 (vesicular monoamine transporter 1; VMAT1) gene has a human‐unique variant (rs1390938, Thr136Ile), which is associated with bipolar disorders and/or the anxiety‐related personality traits. 136Ile shows relatively high (20–61%) frequency in non‐African populations, and Tajima's D reports a significant peak around the Thr136Ile site, suggesting that this polymorphism has been positively maintained by balancing selection in non‐African populations. Moreover, Coalescent simulations predict that 136Ile originated around 100,000 years ago, the time being generally associated with the Out‐of‐Africa migration of modern humans. Our study sheds new light on a gene in monoamine pathway as a strong candidate contributing to human‐unique psychological traits.

Seasonality of cerebrospinal fluid monoamine metabolite concentrations and their associations with meteorological variables in humans

Seasonal variations in neurotransmitter parameters have been previously reported in humans. However, these studies have involved small sample sizes and have not examined possible relationships with meteorological variables. We compared cerebrospinal fluid (CSF) concentrations of the major monoamine neurotransmitter metabolites (5-HIAA, HVA, and MHPG) in 188 healthy controls (80 men, 108 women) in relationship to age, sex, BMI, and available meteorological variables. All subjects had a lumbar puncture (LP) performed at 9 a.m. after overnight stay. Meteorological data for the day prior to LP were obtained from the National Climatic Association and included the photoperiod, percent sunshine, temperature (max, min, mean), barometric pressure, relative humidity, amount of precipitation and sky cover. Results revealed differences across seasons and cross-seasons for CSF 5-HIAA (p ≤ .05), with post-hoc differences emerging between spring versus summer and fall and between x-spring and x-summer (p ≤ .05). Differences were also found across seasons for CSF HVA (p ≤ .05) with post-hoc differences between spring versus fall. CSF 5-HIAA was significantly inversely correlated with maximum (r = -.28, p ≤ .02), minimum (r = -.24, p ≤ .04), and mean temperature (r = -.28, p ≤ .02) in men. In women, 5-HIAA (r = -.22, p ≤ .02) and HVA (r = -.28, p ≤ .003) were significantly correlated with relative humidity. These data confirm previous findings of variations in serotonin and dopamine metabolites across the year and highlight possible underlying mechanisms involving meteorological changes, which may result in alterations in neurophysiology and behavior.

Seasonal mood changes in patients with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is frequently associated with mood disorders. However, to date, the co-occurrence of OCD with seasonal affective disorder (SAD) has not been investigated. We have aimed to estimate the prevalence of seasonal mood changes in patients with OCD and explore the contribution of seasonality in mood to the severity of OCD. The Seasonal Pattern Assessment Questionnaire (SPAQ), the Yale-Brown Obsession and Compulsion Scale (Y-BOCS), the Hamilton Depression Rating Scale-17 Items (HDRS-17), and the Beck Anxiety Inventory (BAI) were administered to patients with OCD (n=104) and controls (n=125). The degree of seasonality was measured by the Global Seasonality Score (GSS) calculated from the SPAQ. SAD and subsyndromal seasonal affective disorder (S-SAD) were significantly more prevalent in patients with OCD (53%, n=55) than controls (25%, n=31). When patients were assessed in the season in which SAD occurs, depression and compulsions (but not obsessions, OCD or anxiety) were more severe than those assessed in a season during which SAD does not occur. SAD frequently co-occurs with OCD and, given this co-occurrence, depression symptoms in some patients with OCD might be expected to vary on a seasonal basis.

The effect of seasonal changes and climatic factors on suicide attempts of young people

BACKGROUND

Seasonal changes and climatic factors like ambient temperature, sunlight duration and rainfall can influence suicidal behavior.

METHODS

This study analyses the relationship between seasonal changes and climatic variations and suicide attempts in 2131 young patients in Istanbul, Turkey.

RESULTS

In our study sample, there was an association between suicide attempts in youths and seasonal changes, as suicide attempts occurred most frequently during summer in females as well as in males. Furthermore, there was a positive correlation between the mean temperature over the past 10 days and temperature at the index day and suicide attempts in females. After seasonality effects were mathematically removed, the mean temperature 10 days before a suicide attempt remained significant in males only, indicating a possible short-term influence of temperature on suicide attempts.

CONCLUSIONS

This study shows an association between suicide attempts of young people and climatic changes, in particular temperature changes as well as seasonal changes. Therefore, the influence of seasonal changes and climatic factors on young suicide attempters should get more attention in research to understand the biopsychosocial mechanisms playing a role in suicide attempts of young people. As suicide attempts most frequently occur in young people, further research is of considerable clinical importance.

Peripheral blood gene expression profiles linked to monoamine metabolite levels in cerebrospinal fluid

The blood-brain barrier separates circulating blood from the central nervous system (CNS). The scope of this barrier is not fully understood which limits our ability to relate biological measurements from peripheral to central phenotypes. For example, it is unknown to what extent gene expression levels in peripheral blood are reflective of CNS metabolism. In this study, we examine links between central monoamine metabolite levels and whole-blood gene expression to better understand the connection between peripheral systems and the CNS. To that end, we correlated the prime monoamine metabolites in cerebrospinal fluid (CSF) with whole-genome gene expression microarray data from blood (N=240 human subjects). We additionally applied gene-enrichment analysis and weighted gene co-expression network analyses (WGCNA) to identify modules of co-expressed genes in blood that may be involved with monoamine metabolite levels in CSF. Transcript levels of two genes were significantly associated with CSF serotonin metabolite levels after Bonferroni correction for multiple testing: THAP7 (P=2.8 × 10^-8, β=0.08) and DDX6 (P=2.9 × 10^-7, β=0.07). Differentially expressed genes were significantly enriched for genes expressed in the brain tissue (P=6.0 × 10^-52). WGCNA revealed significant correlations between serotonin metabolism and hub genes with known functions in serotonin metabolism, for example, HTR2A and COMT. We conclude that gene expression levels in whole blood are associated with monoamine metabolite levels in the human CSF. Our results, including the strong enrichment of brain-expressed genes, illustrate that gene expression profiles in peripheral blood can be relevant for quantitative metabolic phenotypes in the CNS.

Season of Birth Predicts Emotional and Behavioral Regulation in 18-Month-Old Infants: Hamamatsu Birth Cohort for Mothers and Children (HBC Study)

Background

Previous research has demonstrated that the season of birth may predict development of emotional and behavioral regulation during childhood or adolescence. This study examined whether the season of birth predicts effortful control (i.e., the ability to voluntarily choose course of actions during conflict and to plan for the future) and aggression (i.e., the use of physical force and expression of anger toward others) in 18-month-old infants.

Methods

Participants included 885 infants who were enrolled in the Hamamatsu Birth Cohort for Mothers and Children in Hamamatsu, Japan. Seasons of birth were categorized into winter (December, January, and February), spring (March, April, and May), summer (June, July, and August), and autumn (September, October, and November). At 18 months of age, effortful control was assessed using the Early Childhood Behavior Questionnaire, and aggression was measured using the Cardiff Infant Contentiousness Scale. Structural equation modeling analysis with measurement and structural equations was conducted to test our prediction.

Results

Effortful control was higher in infants born in spring [B = 0.095, 95% CI (0.014 to 0.175), p = 0.021, β = 0.146] and summer [B = 0.078, 95% CI (0.001 to 0.156), p = 0.049, β = 0.118] than in those born in winter. In addition, aggression was lower in those born in spring [B = −0.286, 95% CI (−0.551 to −0.021), p = 0.035, β = −0.135] than those born in winter, even after controlling for seven covariates.

Conclusion

The findings suggest that season of birth may determine development of emotional and behavioral regulation skills during early infancy. Future research should pay more attention to the underlying mechanisms of the effects of birth season on development of emotional and behavioral regulation during infancy.

Forecast models for suicide: Time-series analysis with data from Italy

The prediction of suicidal behavior is a complex task. To fine-tune targeted preventative interventions, predictive analytics (i.e. forecasting future risk of suicide) is more important than exploratory data analysis (pattern recognition, e.g. detection of seasonality in suicide time series). This study sets out to investigate the accuracy of forecasting models of suicide for men and women. A total of 101 499 male suicides and of 39 681 female suicides - occurred in Italy from 1969 to 2003 - were investigated. In order to apply the forecasting model and test its accuracy, the time series were split into a training set (1969 to 1996; 336 months) and a test set (1997 to 2003; 84 months). The main outcome was the accuracy of forecasting models on the monthly number of suicides. These measures of accuracy were used: mean absolute error; root mean squared error; mean absolute percentage error; mean absolute scaled error. In both male and female suicides a change in the trend pattern was observed, with an increase from 1969 onwards to reach a maximum around 1990 and decrease thereafter. The variances attributable to the seasonal and trend components were, respectively, 24% and 64% in male suicides, and 28% and 41% in female ones. Both annual and seasonal historical trends of monthly data contributed to forecast future trends of suicide with a margin of error around 10%. The finding is clearer in male than in female time series of suicide. The main conclusion of the study is that models taking seasonality into account seem to be able to derive information on deviation from the mean when this occurs as a zenith, but they fail to reproduce it when it occurs as a nadir. Preventative efforts should concentrate on the factors that influence the occurrence of increases above the main trend in both seasonal and cyclic patterns of suicides.

Suicide and Ambient Temperature in East Asian Countries: A Time-Stratified Case-Crossover Analysis

BACKGROUND

A limited number of studies suggest that ambient temperature contributes to suicide; these studies typically focus on a single nation and use temporally and spatially aggregated data.

OBJECTIVE

We evaluated the association between ambient temperature and suicide in multiple cities in three East Asian countries.

METHODS

A time-stratified case-crossover method was used to explore the relationship between temperature and suicide, adjusting for potential time-varying confounders and time-invariant individual characteristics. Sex- and age-specific associations of temperature with suicide were estimated, as were interactions between temperature and these variables. A random-effects meta-analysis was used to estimate country-specific pooled associations of temperature with suicide.

RESULTS

An increase in temperature corresponding to half of the city-specific standard deviation was positively associated with suicide in most cities, although average suicide rates varied substantially. Pooled country-level effect estimates were 7.8% (95% CI: 5.0, 10.8%) for a 2.3°C increase in ambient temperature in Taiwan, 6.8% (95% CI: 5.4, 8.2%) for a 4.7°C increase in Korea, and 4.5% (95% CI: 3.3, 5.7%) for a 4.2°C increase in Japan. The association between temperature and suicide was significant even after adjusting for sunshine duration; the association between sunshine and suicide was not significant. The associations were greater among men than women in 12 of the 15 cities although not significantly so. There was little evidence of a consistent pattern of associations with age. In general, associations were strongest with temperature on the same day or the previous day, with little evidence of associations with temperature over longer lags (up to 5 days).

CONCLUSIONS

We estimated consistent positive associations between suicide and elevated ambient temperature in three East Asian countries, regardless of country, sex, and age.

CITATION

Kim Y, Kim H, Honda Y, Guo YL, Chen BY, Woo JM, Ebi KL. 2016. Suicide and ambient temperature in East Asian countries: a time-stratified case-crossover analysis. Environ Health Perspect 124:75-80; http://dx.doi.org/10.1289/ehp.1409392.

Reward related neurotransmitter changes in a model of depression: An in vivo microdialysis study

OBJECTIVES

The self-medication hypothesis assumes that symptoms related to potential monoaminergic deficits in depression may be relieved by drug abuse. The aim of this study was to elucidate the neurotransmitter changes in a rat model of depression by measuring their levels in the nucleus accumbens shell, which is typically involved in the drug of abuse acquisition mechanism.

METHODS

Depression was modelled by the olfactory bulbectomy (OBX) in Wistar male rats. In vivo microdialysis was performed, starting from the baseline and following after a single methamphetamine injection and behaviour was monitored. The determination of neurotransmitters and their metabolites was performed by high-performance liquid chromatography combined with mass spectrometry.

RESULTS

OBX animals had lower basal levels of dopamine and serotonin and their metabolites. However, γ-aminobutyric acid (GABA) and glutamate levels were increased. The methamphetamine injection induced stronger dopamine and serotonin release in the OBX rats and lower release of glutamate in comparison with sham-operated rats; GABA levels did not differ significantly.

CONCLUSIONS

This study provides an evidence of mesolimbic neurotransmitter changes in the rat model of depression which may elucidate mechanisms underlying intravenous self-administration studies in which OBX rats were demonstrated to have higher drug intake in comparison to intact controls.

Relationship between sunlight and the age of onset of bipolar disorder: an international multisite study

BACKGROUND

The onset of bipolar disorder is influenced by the interaction of genetic and environmental factors. We previously found that a large increase in sunlight in springtime was associated with a lower age of onset. This study extends this analysis with more collection sites at diverse locations, and includes family history and polarity of first episode.

METHODS

Data from 4037 patients with bipolar I disorder were collected at 36 collection sites in 23 countries at latitudes spanning 3.2 north (N) to 63.4 N and 38.2 south (S) of the equator. The age of onset of the first episode, onset location, family history of mood disorders, and polarity of first episode were obtained retrospectively, from patient records and/or direct interview. Solar insolation data were obtained for the onset locations.

RESULTS

There was a large, significant inverse relationship between maximum monthly increase in solar insolation and age of onset, controlling for the country median age and the birth cohort. The effect was reduced by half if there was no family history. The maximum monthly increase in solar insolation occurred in springtime. The effect was one-third smaller for initial episodes of mania than depression. The largest maximum monthly increase in solar insolation occurred in northern latitudes such as Oslo, Norway, and warm and dry areas such as Los Angeles, California.

LIMITATIONS

Recall bias for onset and family history data.

CONCLUSIONS

A large springtime increase in sunlight may have an important influence on the onset of bipolar disorder, especially in those with a family history of mood disorders.

Seasonal changes in gene expression represent cell-type composition in whole blood

Seasonal patterns in behavior and biological parameters are widespread. Here, we examined seasonal changes in whole blood gene expression profiles of 233 healthy subjects. Using weighted gene co-expression network analysis, we identified three co-expression modules showing circannual patterns. Enrichment analysis suggested that this signal stems primarily from red blood cells and blood platelets. Indeed, a large clinical database with 51 142 observations of blood cell counts over 3 years confirmed a corresponding seasonal pattern of counts of red blood cells, reticulocytes and platelets. We found no direct evidence that these changes are linked to genes known to be key players in regulating immune function or circadian rhythm. It is likely, however, that these seasonal changes in cell counts and gene expression profiles in whole blood represent biological and clinical relevant phenomena. Moreover, our findings highlight possible confounding factors relevant to the study of gene expression profiles in subjects collected at geographical locations with disparaging seasonality patterns.