Biological Influences on Criminal Behavior is a book written by Dr. Gail Anderson, a forensic entomologist and professor at Simon Fraser University. The book describes the impact of biological factors on antisocial behavior. This post has some notes on studies mentioned in the book.
• Evolutionary biology states that behaviors will be selected to maximize Darwinian fitness (survival and reproduction).
• Most crimes are committed by young males during the early reproductive years.
• In almost all cases, MZ twins are at least twice as likely to be concordant for crime as DZ twins, which demonstrates a very powerful genetic component.
• A study of 3586 twin pairs found a much higher concordance in male-male MZ twins for criminal behavior than in male-male DZ twins.
• A study of 246 Iowans adopted at birth found that individuals were found to have a higher level of antisocial behavior when they had biological parents with antisocial behavior.
• A study found that daughters with a criminal biological parent had a threefold increase in criminal behavior over daughters without a criminal biological parent.
• Concordance rates for early-onset antisocial behavior in MZ twins was found to be 55% as compared with 29% in DZ twins.
• A retrospective study of 2682 adult twin pairs from the community-based Australian Twin Registry found a concordance rate of 71% for developing conduct disorder but found little evidence for environmental influences.
• A study of 1116 pairs of 5-year-old twins found that antisocial behavior was very highly heritable, with a heritability estimate of 82%.
• A study that compared 221 pairs of biologically unrelated siblings with 111 pairs of biologically related siblings and 94 singleton children found that genetics accounted for 70% of the variance for aggressive behavior.
• A comparison of MZ and DZ twins found that 70% of the variability in the children’s ability to overcome the detrimental effects of poverty was under the influence of genetics.
• A study of 194 adolescent offenders found that the violent offenders had higher levels of testosterone than nonviolent offenders.
• A study of 4462 inmates found that high levels of testosterone were positive correlated with a variety of problems including delinquency, substance abuse, conflicts with authority figures, and promiscuity.
• A study of incarcerated women found that testosterone was highest in female prisoners who had committed unprovoked assaults, and lowest in inmates who had only reacted violently when they were physically assaulted.
• A study of 692 adult incarcerated men found that offenders convicted of crimes that involved interpersonal violence had higher levels of testosterone than offenders convicted of property crimes or drug offenses.
• A study found that high levels of testosterone were correlated with higher ratings of socially deviant behavior on the Psychopathy Checklist-Revised.
• Low cortisol levels have been reported in habitually violent incarcerated offenders, aggressive school children, adolescents with conduct disorder, and disinhibited children.
• A study found that men who had been juvenile delinquents and had continued this antisocial behavior into adulthood had much higher levels of T3 than either men who were juvenile delinquents but had desisted from this behavior in adulthood or a control group.
• A study found that elevated T3 levels were highly correlated with psychopathy, criminality, and borderline personality disorder.
• A study of 1377 pairs of twins in the Netherlands found that there was a significant effect of maternal smoking on aggressive, overactive, and oppositional behavior problems.
• A study of more than 1000 children in a New Zealand study found that children of mothers who smoked one or more packs of cigarettes a day during their pregnancy were more than twice as likely to develop conduct disorder than children of non-smokers.
• A study of more than 4000 men in Denmark found that maternal smoking during the last 3 months of pregnancy was a significant predictor for adult criminal activity, including both violent and nonviolent crime.
• A study of 129 boys found that there was a strong correlation between minor physical anomalies and violent offending.
• A longitudinal Canadian study of 170 adolescent males found that minor physical anomalies around the mouth showed the highest correlation with violence.
• A study of 4269 males in Denmark who had complications in their births and were rejected by their mothers before age 1 found that there was a significant interaction between birth complications and early rejection in predicting violence at 34 years.
• Lower levels of serotonin have been associated with increased aggression, irritability, hostility, and impulsivity.
• A study found that high HVA:5-HIAA ratios strongly correlated with psychopathy, suggesting that aggressive psychopathy may be related to both lowered serotonin levels and high levels of dopamine in the brain.
• A study of violent offenders in a Finnish forensic facility found that CSF levels of the serotonin metabolite 5HIAA were significantly lower in repeat violent offenders compared with those who had committed only one violent crime.
• A study in Finland found that 80 to 85% of recidivist severe violent crimes are thought to be committed by people with antisocial personality disorder.
• A study of boys with ADHD found that aggressive boys with aggressive parents had significantly lower serotonin function than aggressive boys with nonaggressive parents.
• A study found that persistent and pervasively aggressive children were more likely to carry a particular MAOA allele that results in higher levels of MAOA transcription than that seen in normal adults.
• A study of male adult New Zealanders found that 85% of the severely abused participants with the low-activity variant of the MAOA gene developed some form of antisocial behavior. In contrast, participants who had the fully functioning variant of the gene rarely exhibited aggressive or criminal behavior as adults, even if they had been severely abused as children.
• A study of 514 male twins between the ages of 8 and 17 years found that children with the low-activity variant of the MAOA gene who also experienced childhood adversity were significantly more likely to develop conduct disorder. However, children with the same gene variant who experienced happy childhoods in stable homes had a lower risk of conduct disorder.
• A study found that life-course persistent and late-onset antisocial individuals were taller and bulkier than adolescent-limited antisocial or control individuals.
• A study of 15 death row inmates found that all had suffered serious head injuries prior to their offense.
• A study of 14 juveniles on death row found that all of them had a history of past severe head injuries.
• Studies of non-incarcerated individuals found that the majority of men with problems of aggression against their families had suffered severe head injury.
• A study of partner-abusive men found that 92% of the men had suffered from a head injury before they began abusing their parters.
• A studying using MRI found a correlation between higher psychopathy scores and reduced volume in the posterior half of the hippocampus.
• A MRI study examined the corpus callosum region in psychopaths and found that psychopaths have an increased white matter volume as well as an increased callosal length, but reduction in thickness, with increased connectivity between the two hemispheres.
• A fMRI study of psychopaths found that they showed greatly reduced emotional response in several areas of the limbic region of the brain when responding to negative verbal stimuli.
• A PET study of murderers found that they had significantly lower brain activity in the prefrontal cortex, the superior lateral parietal gyrus, the left angular gyrus, and the corpus callosum. They had higher glucose metabolism in the occipital region.
• A PET study found that predatory murderers had no significant abnormalities in the prefrontal cortex (although they did have excessive subcortical activity in the right hemisphere) whereas impulsive murderers had low frontal activity.
• A study of violent offenders found a strong relationship between reduced frontal and temporal lobe activity and high PCL-R scores.
• Studies link low blood sugar (hypoglycemia) to violent or aggressive behavior.
• A study found that a low sugar diet reduced antisocial behavior in incarcerated juveniles by 48%.
• A study measured both blood sugar and serotonin levels and was able to predict which subjects were repeat, alcohol-abusing, violent offenders and impulsive fire-setters in 84.2% of cases.
• In a human study, a significant increase in aggression was noted in normally healthy males after they consumed a tryptophan-free amino acid mixture and during a period where the subjects were on a low tryptophan diet.
• A study found that lead poisoning was the strongest predictor of disciplinary problems in school, which in turn were the strongest predictor of arrests between the ages of 7 and 22 years.
• In Britain, researchers found significant relationships between lead levels assessed from blood in a large sample of over 500 children aged 6 to 9 years and teacher and parent ratings of aggressive and antisocial behavior.
• A study followed a group of 195 children from pre-birth to adolescence and showed a strong correlation between lead levels and delinquency.
• A study compared 194 convicted juvenile offenders with 146 control adolescents and found that the offenders were four times more likely to have high lead levels.
• A study of 30 violent adult criminal offenders found that they had significantly higher levels of lead and cadmium than a control group.
• An analysis of air lead levels found that homicide levels were nearly 4 times higher in countries with maximum air lead concentrations than in the countries with the lowest levels.
• Even low exposure to manganese is related to loss of impulse control and outbursts of violent behavior.
• At least seven studies of prison inmates have found that hair levels of manganese, lead, and/or cadmium were significantly higher in violent offenders than in nonviolent offenders or controls.
• The cellular uptake of manganese from soy formula is 20 times greater than from mother’s milk.
• A study found that vitamin and mineral supplementation led to a 16-point gain in IQ in some children compared to the placebo group.
• Low serum cholesterol concentrations are common among persons who characteristically engage in violent behavior.
• A study of 3600 young urban adults found that higher consumption of the omega-3 fatty acid DHA was significantly related to lower levels of hostility.
• A study of hyperactive children with known sensitivities to synthetic food colorings found that when exposed to the food coloring tartrazine, 16 of the 23 children became aggressive and 4 became violent.
