A formula for violence:

Jacob Schor, ND, FABNO


September 10, 2013


Denver sweated its way through another heat wave last week, breaking heat records that go back a hundred years.  It hit 95 degrees Saturday, marking the third day in a row the city has tied or beat record-highs. The Sept. 7 record was set at 95 degrees in 1933.  The normal, or average, high for Sept. 7 is in the lower-80s.




At the same time as heat records were melting away, both East High and Manual high schools were closed Friday out of fear of gang violence, postponing Manual’s Homecoming Dance. “Police spokesman John White would not elaborate on the nature of the threats except to say that the one at East was made against the school in general, not a particular individual. Not details were given, just that there was a "credible threat" at the schools Manual also postponed its Saturday night homecoming dance, citing "safety concerns."






These two seemingly unrelated events bring to mind a paper that appeared last August 2 in the journal Science in which Solomon Hsiang attempts to quantify the influence of climate on human conflict.  We take it for granted that hot weather begets an increase in violent behavior whether we are reading murder mysteries of the Denver Post. 


Hsiang has put numbers to this equation.


Analyzing data from 60 earlier studies, Hsiang along with colleagues Marshall Burke, and Edward Miguel from the University of California, Berkeley, found that warmer temperatures and extremes in rainfall can substantially increase the risk of many types of conflict. For every standard deviation of change, levels of interpersonal violence, such as domestic violence or rape, rise by some 4 percent, while the frequency of intergroup conflict, from riots to civil wars, rise by 14 percent. Global temperatures are expected to rise by at least two standard deviations by 2050, with even bigger increases in the tropics



“The researchers ignored studies that compared levels of conflict between different countries, which also differ in their history, culture, and politics. Instead, they focused on data that revealed how violence rises and falls in a single place as climate changes.


For example, crime statistics in the United States reveal that the number of rapes, murders, or assaults increases on a hot day. Civil conflicts in the tropics become twice as frequent during the hot and dry years caused by El Niño events. Farmers in Brazil are more likely to invade each other’s land if they have a particularly wet or dry year. And Chinese dynasties all collapsed during long dry periods.

The team analyzed these studies and more using a common statistical framework to control for any biases on the part of the individual authors. Together, the data sets stretch back to 10,000 BC, and cover all major world regions. They represent the collective efforts of more than 190 researchers working across varied disciplines, from psychologists looking at the effects of temperature on aggressive behavior to archaeologists studying levels of violence in the ancient civilizations.

Despite this diversity, “we were shocked at how well the results from all these fields lined up,” said Hsiang. “Given how some people had been talking, we thought they’d be all over the map,” but the data consistently showed that temperature and rainfall affect violence, across locations, times and disciplines.”




Try this:

Google “Heat Wave 2013”

It isn’t just Denver that’s had a hot summer.  Most of the US has.  Not to mention China where temperatures broke 140 year records or Japan, Singapore and Austria;  all are having heat waves.  And we thought this was just local.


[Here comes a weak transition to another topic and another recent study of interest.  I am not pretending that these are related topics, but watch me try and tie them together anyway]


Could there be a simple cure?  Is there some way to put the ‘chill’ on people and reduce this tendency to violence triggered by heat?  Insist that people live in air-conditioned cities, spend time in swimming pools or drinks lots of cold drinks?


Perhaps the ubiquitous advertising by Pepsi and Coke has had the desired effect as I find myself asking Google to look for “Cold drinks reduce violent behavior.”


Instead of the hoped for cure, the opposite seems to be true.  The problem is that people no longer reach for ice water when they are hot and thirsty, they grab a soda.  At least in children, soda consumption is directly associated with more violent behavior.


“Americans buy more soft drinks per capita than people in any other country. These drinks are consumed by individuals of all ages, including very young children. Although soft drink consumption is associated with aggression, depression, and suicidal thoughts in adolescents, the relationship had not been evaluated in younger children. A new study in The Journal of Pediatrics finds that aggression, attention problems, and withdrawal behavior are all associated with soft drink consumption in young children.


“Shakira Suglia, ScD, and colleagues from Columbia University's Mailman School of Public Health, University of Vermont, and Harvard School of Public Health assessed approximately 3,000 5-year-old children enrolled in the Fragile Families and Child Wellbeing Study, a prospective birth cohort that follows mother-child pairs from 20 large U.S. cities. Mothers reported their child's soft drink consumption and completed the Child Behavior Checklist based on their child's behavior during the previous two months. The researchers found that 43% of the children consumed at least 1 serving of soft drinks per day, and 4% consumed 4 or more.

Aggression, withdrawal, and attention problems were associated with soda consumption. Even after adjusting for sociodemographic factors, maternal depression, intimate partner violence, and paternal incarceration, any soft drink consumption was associated with increased aggressive behavior. Children who drank 4 or more soft drinks per day were more than twice as likely to destroy things belonging to others, get into fights, and physically attack people. They also had increased attention problems and withdrawal behavior compared with those who did not consume soft drinks,

According to Dr. Suglia, "We found that the child's aggressive behavior score increased with every increase in soft drinks servings per day." Although this study cannot identify the exact nature of the association between soft drink consumption and problem behaviors, limiting or eliminating a child's soft drink consumption may reduce behavioral problems.”





That’s enough ruminating for one day.  Lucky for Denver the weather has cooled down today and we’re back to normal September temperatures. 






Hsiang, Solomon M., Marshall Burke, and Edward, Miguel. 2013. "Quantifying the Influence of Climate on Human Conflict." Science, 10.1126/science.1235367.



Shakira F. Suglia, Sara Solnick, and David Hemenway. Soft Drinks Consumption Is Associated with Behavior Problems in 5-Year-Olds. The Journal of Pediatrics, 2013 DOI: 10.1016/j.jpeds.2013.06.023