Linkages between climate and mental health are often theorized 1, 2 but remain poorly quantified. 3 In particular, it is unknown whether suicide, a leading cause of death globally, 4 is systematically affected by climatic conditions. Using multiple decades of comprehensive data from both the US and Mexico, we find that suicide rates rise 0.7% in US counties and 2.1% in Mexican municipalities for a 1 • C increase in monthly average temperature. This effect is similar in hotter versus cooler regions and has not diminished over time, indicating limited historical adaptation. Analysis of depressive language in >600 million social media updates further suggests that mental wellbeing deteriorates during warmer periods. We project that unmitigated climate change (RCP8.5) could result in a combined 9-40 thousand additional suicides (95% CI) across the US and Mexico by 2050, representing an change in suicide rates comparable to the estimated impact of economic recessions, 5 suicide prevention programs, 6 or gun restriction laws. 7 Climate is increasingly understood to influence many dimensions of human health, 1, 8, 9 affecting health outcomes ranging from vector-borne disease mortality to rates of cardiac arrest. 9, 10 These relationships have been shown to occur through direct physical stress or insults to the body (e.g. heatstroke or cyclone-caused drowning), changes in disease ecology (e.g. seasonal flu or malaria), and/or changes in socioeconomic conditions that support human health (e.g. drought-induced famine). Recent work has also demonstrated that social conflicts between individuals, which cause intentional injuries and mortality, are particularly responsive to changes in temperature, perhaps due to changes in underlying economic conditions or altered individual-level aggressiveness. 11 Potential linkages between climatic conditions and mental health are also increasingly hypothesized. 3 However, unlike other key health outcomes, there remains limited quantitative evidence linking temperature to suicide and related mental health outcomes. 12, 13 Determining whether or not suicide responds to climatic conditions is important, as suicide alone causes more deaths globally than all forms of interpersonal and intergroup violence combined, 4 is among the top 10-15 causes of death globally, among the top 5 causes of lost life-years in many wealthy regions, 14 and among the top 5 causes of death for individuals aged 10-54 in the US. 15 It is the only cause of death among the top 10 in the US for which age-adjusted mortality rates are not declining. 16 Thus even modest changes in suicide rates due to climate change could portend large changes in the associated global health burden, particularly in wealthier countries where current suicide rates are relatively high and/or on the rise.

We evaluate the impact of an educational program that aims to build social cohesion in ethnically mixed schools by developing perspective-taking ability in children. The program is implemented in Turkish elementary schools affected by a large influx of Syrian refugee children. We measure a comprehensive set of outcomes that characterize a cohesive school environment, including peer violence incidents, the prevalence of interethnic social ties, and prosocial behavior. Using randomized variation in program implementation, we find that the program significantly lowers peer violence and victimization on school grounds. The program also reduces the likelihood of social exclusion and increases interethnic social ties in the classroom. We find that the program significantly improves prosocial behavior, measured by incentivized tasks: treated students exhibit significantly higher trust, reciprocity, and altruism toward each other as well as toward anonymous out-school peers. We show that this enhanced prosociality is welfare improving from the ex post payoff perspective. We investigate multiple channels that could explain the results, including ethnic bias, impulsivity, empathetic concern, emotional intelligence, behavioral norms, and perspective taking. Children’s increased effort to take others’ perspectives emerges as the most robust mechanism to explain our results.

I evaluate randomly varied neighborhood exposure to information campaigns regarding either executive performance, or increases in executive power, prior to a Turkish referendum on weakening checks and balances on the executive. The campaigns increased voter polarization over the referendum, and subsequently changed party affiliation in national and local elections over the next two years, leading to partisan polarization. My results suggest that, when voters disagree on whether increasing executive power is a good policy, more information can increase voter polarization. Finally, I conclude that because potential polarization is often ignored, the impact of information campaigns on civil society is underestimated. (JEL D72, D83, O17)

Organized intergroup violence is almost universally modeled as a calculated act motivated by economic factors. In contrast, it is generally assumed that non-economic factors, such as an individual's emotional state, play a role in many types of interpersonal violence, such as "crimes of passion." We ask whether non-economic factors can also explain the well-established relationship between temperature and violence in a unique context where intergroup killings by drug-trafficking organizations (DTOs) and other interpersonal homicides are separately documented. A constellation of evidence, including the limited influence of a cash transfer program as well as comparisons with both other DTO crime and suicides, indicate that economic factors only partially mitigate the relationship between temperature and violence that we estimate in Mexico. We argue that non-economic psychological and physiological factors that are affected by temperature, modeled here as a "taste for violence," likely play an important role in causing both interpersonal and intergroup violence.

Organized intergroup violence is almost universally modeled as a calculated act motivated by economic factors. In contrast, it is generally assumed that non-economic factors, such as an individual's emotional state, play a role in many types of inter-personal violence, such as "crimes of passion." We ask whether economic or non-economic factors better explain the well-established relationship between temperature and violence in a unique context where intergroup killings by drug-trafficking organizations (DTOs) and "normal" interpersonal homicides are separately documented. A constellation of evidence, including the limited influence of a cash transfer program as well as comparison with both other DTO crime and suicides, indicate that economic factors only partially explain the observed relationship between temperature and violence. We argue that noneconomic psychological and physiological factors that are affected by temperature, modeled here as a "taste for violence," likely play an important role in causing both interpersonal and intergroup violence.