Annual fluctuations of sunlight and suicides in a region South of the Tropic of Cancer

Socioeconomic and environmental contexts of suicidal rates in a latitudinal gradient: Understanding interactions to inform public health interventions

Suicide results from complex interactions between biological, psychological, and socioeconomic factors. At the population level, the study of suicide rates and their environmental and social determinants allows us to disentangle some of these complexities and provides support for policy design and preventive actions. In this study we aim to evaluate the associations between environmental and socioeconomic factors and demographically stratified suicide rates on large temporal and spatial scales. Our dataset contains information about yearly suicides rates by sex and age from 2000 through 2017 along a 4000 km latitudinal gradient. We used zero-inflated negative binomial models to evaluate the spatio-temporal influence of each environmental and socioeconomic variable on suicide rates at each sex/age combination. Overall, we found differential patterns of associations between suicide rates and explanatory variables by age and sex. Suicide rates in men increases in middle and high latitude regions and intermediate age classes. For adolescent and adult women, we found a similar pattern with an increase in suicide rates at middle and high latitudes. Sex differences measured by the male/female suicide ratio shows a marked increase with age. We found that cloudiness has a positive effect on suicide rates in both men and women 24 years old or younger. Regional poverty shows a major impact on men in age classes above 35 years old, an effect that was absent in women. Alcohol and marijuana consumption showed no significant effect sizes. Our findings support high spatio-temporal variability in suicide rates in interaction with extrinsic factors. Several strong differential impacts of environmental and socioeconomic variables on suicide rates depending on sex and age were detected. These results suggest that the design of public policies and interventions to reduce suicide prevalence need to consider the local social and environmental contexts of target populations.

Influence of contextual factors on death by suicide in rural and urban settings

PURPOSE

To examine the association between contextual factors, represented by geographic and community health variables, and suicide among rural and urban Department of Veterans Affairs health care users (VA users).

METHODS

We performed a retrospective cohort study of 12,700,847 VA users between 2003 and 2017. We assigned contextual factors based on individuals' home address at the ZIP Code (area deprivation), county (sunlight exposure, altitude, and community health), and state level (firearm ownership), using publicly available data sources. We grouped contextual factors by quintiles or prespecified thresholds, depending on the nature of each variable. We obtained mortality data from the National Death Index. We measured the effect of living in a place with the highest versus lowest level of each contextual factor on odds of suicide using logistic regression, adjusting for individual compositional factors abstracted from VA electronic medical records data. We used random forest modeling to build prediction models for suicide based on contextual factors among rural and urban veterans.

FINDINGS

Almost all contextual factors we examined were significantly associated with suicide among rural and urban VA users, even after adjusting for individual compositional factors. However, no contextual variables were strong protective or risk factors (0.5<OR>2.0), and prediction models leveraging these contextual factors had poor accuracy among both rural (0.51, 95% CI: 0.48-0.54) and urban (0.53, 95% CI: 0.51-0.55) VA users.

CONCLUSIONS

A wide variety of contextual factors is significantly associated with suicide among rural and urban VA users. However, the factors we measured contributed very little to individual-level suicide risk.

Temporal patterns of suicide and circulatory system disease-related mortality are inversely correlated in several countries

BACKGROUND

Nearly 800,000 suicides occur worldwide annually and suicide rates are increasing faster than population growth. Unfortunately, the pathophysiology of suicide remains poorly understood, which has hindered suicide prevention efforts. However, mechanistic clues may be found by studying effects of seasonality on suicide and other mortality causes. Suicides tend to peak in spring-summer periods and nadir in fall-winter periods while circulatory system disease-related mortality tends to exhibit the opposite temporal trends. This study aimed to determine for the first time whether monthly temporal cross-correlations exist between suicide and circulatory system disease-related mortality at the population level. If so and if common biological factors moderate risks for both mortality types, such factors may be discoverable and utilized to improve suicide prevention.

METHODS

We conducted time series analyses of monthly mortality data from northern (England and Wales, South Korea, United States) and southern (Australia, Brazil) hemisphere countries during the period 2009-2018 (N = 41.8 million all-cause mortality cases). We used a Poisson regression variant of the standard cosinor model to determine peak months of mortality. We also estimated cross-correlations between monthly mortality counts from suicide and from circulatory system diseases.

RESULTS

Suicide and circulatory disease-related mortality temporal patterns were negatively correlated in Australia (- 0.32), Brazil (- 0.57), South Korea (- 0.32), and in the United States (- 0.66), but no temporal correlation was discernable in England and Wales.

CONCLUSIONS

The negative temporal cross-correlations between these mortality types we found in 4 of 5 countries studied suggest that seasonal factors broadly and inversely moderate risks for circulatory disease-related mortality and suicide, but not in all regions, indicating that the effect is not uniform. Since the seasonal factors of temperature and light exert opposite effects on suicide and circulatory disease-related mortality in several countries, we propose that physiologically-adaptive circulatory system responses to heat and light may increase risk for suicide and should be studied to determine whether they affect suicide risk. For example, heat and light increase production and release of the bioactive gas nitric oxide and reduce circulatory system disease by relaxing blood vessel tone, while elevated nitric oxide levels are associated with suicidal behavior, inverse effects that parallel the inverse temporal mortality patterns we detected.

Timing of suicide in people with epilepsy: A population-based study from 18 states of the United States, 2003-2014

Suicide timing varies across several psychiatric disorders, which may share common underlying pathophysiological mechanisms with epilepsy. We investigated suicide timing in people with epilepsy. Using cross-sectional, population-based U.S. National Violent Death Reporting System data from 2003 through 2014 in 18 States, we identified 1310 suicides with epilepsy and 102,582 suicides without epilepsy among those 10 years and older. We compared patterns of suicide mortality ratios between those with and without epilepsy by month of year, week of month, day of week, time of day, and overall by age, sex, and race/ethnicity. As the suicide patterns seen among persons without epilepsy, suicides in persons with epilepsy occurred significantly more often during the morning, afternoon, and evening hours than at night in all subgroups except females. Compared to Sundays, suicides in persons with epilepsy were only significantly increased on Mondays and Tuesdays in those aged ≥45 years and only on Mondays in men. This pattern differs from persons without epilepsy whose suicides significantly increased on Mondays and significantly decreased on Saturdays in nearly all study subgroups. Suicides in persons with epilepsy did not exhibit the timing patterns of persons without epilepsy by week of month (significant decreases from the third to fifth weeks compared to the first week among those aged ≥45 years, males, and Non-Hispanic whites) and month of year (significant increases from January to November peaking from June to September compared to December in all study groups). Compared to the general population or people without epilepsy, previous and current studies suggest that in people with epilepsy, suicide timing differs from and suicide rates significantly exceed those in people without epilepsy. Preventing suicide in people with epilepsy should focus not only on the peak times of occurrence but also across all time periods.