Monday, 19 June 2017

Murderino Monday: “How did we survive the 70s?”


Something that’s popped up in the podcast is the upswing of murders in the 60s and 70s; now I’m not sure if I heard it on MFM or read it somewhere else but there’s a theory it may have had something to do with untreated PTSD from the war – it led to aggression and desensitization to death and those two combined led to possible reasons for why so many serial killers were around. Interesting, and worth looking into – but that’s not what I’m going to be discussing today. Instead, I’ve chosen an alternative theory – lead poisoning and IQ.



Lead poisoning was a big thing last century, the way things were going it would’ve been considered a hot trend. The 60s and 70s were a wild time for lead, it was used in everything, but the biggest use in America was gasoline. Emissions were everywhere, polluting the streets of America and unknowingly creating a bunch of killers. Let’s start at the beginning: Childhood and IQ.

IQ – Intelligence Quotient – has been a subject of hot debate: does it really measure intelligence? Is intelligence objective? What does it really mean? It’s been the most researched means of measuring intelligence and is used everywhere, but while it aims to be objective, how can you measure intelligence of creativity? It’s believed to be used as a measure of standard achievements but not a true measure of intelligence, which is understandable. There have been cases of those with low IQ but having incredible talent and achieving unbelievable things – see: Alonzo Clemons (an IQ of 40 – 50 but a sculptor and savant). Generally, you can say IQ is a measure of social functioning and standard achievements, but to claim intelligence is a little bit of a stretch (in this context).


Higher levels of lead in children’s blood concentrations led to a decrease of intelligence and attention concentration function – IQ points deteriorated by over 5 points. Very young children are particularly susceptible of this, with lead exposure before the age of 3 leading to extreme IQ changes due to the developmental nature of an infant’s brain. Interestingly, temporal studies found a correlation between lead exposure and crime, looking at rape, aggravated assault, murder and robbery. Aggravated assaults and rape were the most strongly linked, but links were still seen between murder and use of lead gasoline. In the 90s, lead gasoline started to be phased out and that’s when the decrease in these assaults were seen. Huge changes in murder rates were found with around 1 murder per 100,000 inhabitants taking place on average now, compared to the 10/100,000 when 1.5 tonnes of lead were being pumped out (compared to the .01 now).


Lead exposure has been found to cause problems with cognition, social behaviour and motor abilities, and adults exposed to lead during childhood showed neuroanatomical abnormalities. The study in question found areas like the prefrontal cortex and anterior cingulate cortex have significant decrease in volume – areas that are responsible for mood, executive functions and decision making (also the same exact finding in a research project I was a part of on schizophrenia research – but that’s for another time!). The findings indicate childhood exposure to lead had an effect on the brain development, leading to these volumetric changes.


Interestingly, a study looking at volumetric differences between violent cases of antisocial personality disorder (sociopathy) and schizophrenia, found that those with ASPD showed cortical thinning in parts of the prefrontal cortex – specifically related to violence, which can indicate problems with judgement, emotion and impulsivity. So if lead poisoning has an effect on these areas of the brain volumetrically, then it’s no wonder that it lead to violent outbreaks during the time lead was heavily used.


While this theory may hold a bit of water with the extensive surrounding literature, it’s also important to remember correlation does not always equal causation, and socially and culturally things were changing at the time which may have also contributed, like the oil crisis, war/anti-war movements and the great depression. Plenty of things may have contributed to the rise in murder during this period but it’s hard to ignore the amount of evidence pointing towards lead exposure.

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