Homicide Rates Hit 25-year High; These Are Some Biological Factors Behind It

Police tape secures a crime scene outside a club after a shooting in New York City in a file photo. Johannes Eisele/AFP via Getty Images

Violence in the United States has been increasing.

The country is now seeing a return to the violence-ridden landscapes of the ‘90s. The Centers for Disease Control and Prevention’s 2020 violent crimes data revealed that homicide rates are skyrocketing and are at the highest rate in more than 25 years, increasing by at least 20 to 25 percent per state.

2022 does not seem to bode well for Americans either. Violence is spilling into the younger generations, with teenagers and young adults becoming perpetrators to the year’s most horrific mass shootings so far.

Violence-rampant areas are also seeing increased rates of violence while spreading into new areas that have normally had lower rates of violent crimes.

Though two years of the COVID-19 pandemic and lockdowns have likely contributed to the growing social unrest, the widespread violent crimes that are appearing in the United States like a growing infection require a closer evaluation to identify if there are other causes which the pandemic may have exacerbated.

In this article, we aim to address some of the underlying health and biological factors that can lead to mood disorders and aggression, and attempt to explain the rising social agitation we are seeing at the population level.

5-mg pills of Oxycodone. Keith Srakoci/AP Photo/The Canadian Press

Drugs

Drugs change our brain chemistry and can have far-reaching effects on our mental and physical health. Most drugs affect our mood and are implicated in mood disorders and aggression. Some drug users become violent in the process of getting drugs, and for others, aggression is a side effect of drug use.

Substance abuse is undoubtedly implicated in violence and violent crime. A 2007 survey (pdf) found that 26 percent of victims of violence reported that their perpetrator were under the influence of drugs or alcohol. Drug use was exacerbated during the COVID-19 lockdowns, with psychologists reporting increased incidence of substance abuse disorders among their patients.

• Alcohol

It is well known that alcohol, consumed in large quantities, is damaging to the brain.

Alcohol is a depressant, meaning it slows the nervous system down. Alcohol consumption reduces dopamine receptors and therefore reduces dopamine release. Long-term consumption also reduces serotonin levels, leading to depression and aggression.

Researchers suggest alcohol consumption in the short-term can lead to a self-focused view, making the individual less aware and conscious of their surroundings, and therefore of their behavior.

Alcohol also reduces the activity of the prefrontal cortex which inhibits impulses, increasing the likelihood of exhibiting inappropriate behaviors.

Higher risks of violence are also related to heavy drinking: 48 percent of incarcerated homicides were committed during or after alcohol ingestion.

In individuals who are not normally aggressive, alcohol may exacerbate their hostile bias, making them interpret ambiguous situations as aggressive rather than benign.

Like most drugs, alcohol is neurotoxic, meaning that it alters the activity and functions of neurons and can cause them to die. In the long-term, moderate to high alcohol consumers have reduced volumes in the prefrontal cortex—the area responsible for decision making and impulse control.

A bottle of antidepressant pills Effexor in Miami, Fla., on March 23, 2004. Joe Raedle/Getty Images

• Antidepressants

Research has shown that depressed people often have low serotonin, therefore antidepressants that increase serotonin levels have been promoted to improve people’s mood by improving serotonin levels.

Popular antidepressants include serotonin re-uptake inhibitors (SSRI)—drugs that prevent neurons from taking up serotonin in order to prolong the action of serotonin in nerve cell to cell communication.

Side effects of the SSRI drugs include confusion, nausea, headache, shaking (tremors), and anxiety.

However, significant cases of adverse events that report emotional numbness, aggression, agitation, hallucination, and sleep impairment in individuals treated with SSRIs suggest that the mechanism of action of serotonin is more nuanced in effect.

In numerous clinical studies (pdf), adolescences displayed mania, violence, and suicidal ideation and attempts after taking SSRIs, with participants exhibiting increased acts of self-harm compared to adolescents who were given a placebo.

A study in 2006 on SSRIs and legal cases extensively documented homicide cases that detected or involved antidepressants.

• Opioids

One-time use of opioids often reduces aggression, hostility, and creates feelings of euphoria. However, with chronic use, the drug’s direct effects on mood significantly changes as tolerance develops, with euphorigenic effects often replaced with feelings of anxiety, agitation, muscle, and stomach pain during withdrawal.

Opioids act on the brain by binding to opioids receptors that release dopamine to create a sense of pleasure. It also reduces norepinephrine release in locus coeruleus neurons. Norepinephrine causes wakefulness and alertness, opioids reduce these. However, repeated exposure to opioids cause the neurons to adjust by increasing their level of activity.

Opioids’ suppressive actions will now be offset as the neurons adapt.  Therefore, for opioid users, the “normal” they experience is when they are using the drugs.

As the body gets used to opioids, its euphoric and pain relieving effects may wane which drives the user’s need for more opioids in order to obtain euphoric effects. Some research shows that this need for more drugs may be linked with opioid users’ crime participation. Users are also more likely to carry guns and be afflicted by injury from gun violence.

Aggression as part of opioid withdrawal is well established. When opioid users go into withdrawal, the overactive neurons in the locus coeruleus create sensations of anxiety, irritation, and other withdrawal symptoms, which can lead to aggression or violence. Severe withdrawal effects are why opioid addictions are so difficult to treat.

Most studies have shown that long-term opioid users have reduced grey matter volume in the pre-frontal cortex; other studies have also shown reductions in the amygdala, an area where emotions are processed, and also in the reward centers of the brain.

• Amphetamines

The relationship between amphetamines (Adderall, Dexedrine, ecstasy) and aggression are not well established but studies on animal models have shown that an acute dose of amphetamine can increase defensive and aggressive behaviors, paranoia, as well as irritability in a dose-dependent manner.

Amphetamines are often prescribed to give a sense of alertness, wakefulness, improve attention deficits, increase cognitive control, among others. Unfortunately, amphetamines can also be obtained illegally.

Chronic use of amphetamines impairs impulse control in the brain, and some studies relate amphetamine use with paranoia, the perception that the environment is hostile.

Like most drugs with abuse potential, amphetamines are neurotoxic. Long-term users have reduced grey matter volume in the outer layers of the brain, especially the pre-frontal area which is responsible for impulse control, as well as higher striatal volume. High striatal volume has been linked with impulsivity.

• Testosterone

High levels of testosterone also increase aggressive behavior. Testosterone is a male sex hormone. During embryonic development, testosterone promotes the  growth of the external male genitalia.

Adult brain scans have shown that testosterone activates the amygdala, the emotional center within the brain. Testosterone enhances amygdala activity and reduces prefrontal control over impulse and emotions, increasing the likelihood of decisions made in an impulsive and emotional manner rather than logical.

Though testosterone is mostly associated with the male sex, females also produce the hormone in the ovaries and the adrenal glands. Compared to males, studies in primates suggest females are more sensitive and are more prone to aggression when testosterone levels are elevated.

Transgender males are often warned before they go into treatment of an increase in aggressive behaviors.

Diet

What we eat very much influences the way we feel. A well-made home cooked meal brings us the sense of warmth and love of home, but unpalatable and unfamiliar food can create senses of displeasure.

Additionally, the chemical molecules in our food can also intrinsically affect our mood.

Highly processed foods are having a negative effect on our health. Hamza NOUASRIA/Unsplash

• Processed Food

Processed food have been linked with increased aggressive behaviors due to added additives and low nutrition value.

Highly processed food is often high in trans fatty acids, sugar, aspartame (sweetener), and monosodium glutamate (MSG), all of which have been linked with mood disorders and aggression.

Processed food is common in prisons, and a major complaint among inmates is the lack of wholesome, nutritional food. Research suggests that the poor nutritional quality of prison food contributes to prison violence and suicides.

Apart from poor nutrition, many additives in processed food pose major health risks.

Extensive studies on MSG and aspartame have demonstrated its toxic effects to the body.

MSG toxicity can cause (with consumption of more than 3 grams) muscle weakness, headache, flushing, and body numbness, among others, while aspartame toxicity has been documented to include symptoms of breathlessness, abdominal pain, seizures, anxiety, irritability, and many more.

Both additives are excitotoxins, chemicals that normally act as excitatory neurotransmitters in the brain. In excessive amounts, excitotoxins can lead to an over activation of neurons and cause exhaustion and cell death. MSG is the most prevalent food additive, present in Pringles, KFC, and just about any popular fried food one can name. A 2006 report found aspartame in around 6,000 products consumed by over 200 million people, though it is highly likely that that the number is actually higher.

Aspartame (NutraSweet, Equal, and Sugar Twin) is often added to processed food as a sugar replacement. The artificial sweetener is 180 to 200 times sweeter than refined sugar, and is therefore highly prevalent in “low-sugar” and “reduced sugar” foods such as sodas and yoghurts.

Once ingested, aspartame breaks down into phenylalanine (50 percent), aspartic acid (40 percent) and methanol (10 percent).

In the body, methanol is metabolized to toxic metabolites called formaldehyde (used as a disinfectant and a preservative in mortuaries) which is then broken down into formic acid (corrosive chemical used in disinfectants) and finally into folic acid.

Phenylalanine and aspartic acid can inhibit the production and release of common neurotransmitters such as dopamine, norepinephrine, and serotonin.

Dopamine can act both as an excitatory (activate) or inhibitory (deactivate) neurotransmitter. It acts in the reward pathway and is involved in motivations and mood regulation. Norepinephrine increases alertness and attention while serotonin controls sleep, digestion, and is also a mood regulator.

Both low serotonin and dopamine have been linked with mood disturbances, impulsivity, and aggression which explains why aspartame has been linked with behavioral problems.

MSG is used in the place of salt in highly processed food. It has an umami taste and is used to enhance the savory flavor and aroma of processed meats, soups, stews, and many other foods.

Due to the extensive campaigns against food with high salt content, MSG has been increasingly used as a salt replacement.

However, consumption of MSG is strongly associated with cellular stress, and studies in the laboratory have shown that MSG can cause deaths of neurons.

Animal studies have found that MSG increases depression, aggression, and violence. MSG breaks down in the body as sodium and glutamate, increasing glutamate signaling.

Glutamate acts as an excitatory neurotransmitter and impaired glutamate signaling has been linked with psychotic disorders including schizophrenia, as well as learning and memory disorders. The exact mechanism of how MSG causes such behaviors is not well defined.

• Sugar

Highly processed foods are also high in added sugar. The body readily digests it leading to spikes in blood sugar levels.

Though the sugar in natural whole foods such as apples and oranges is molecularly the same as added sugar, consumption of such foods provides health benefits in the form of vitamins, minerals, and fiber. However, added sugar in processed food is high in calories with little nutritional benefit.

Unstable blood sugar levels—common for people with diabetes—are contributors to aggression or violence, especially when blood sugar dramatically drops.

The sugar in fruits are also locked up in the plant cells and blood sugar levels will rise more slowly as the fruit is slowly digested. Processed foods, however, are not only low in nutrients but are quickly broken down, causing sharp increases in blood sugar levels, creating a sugar “high.”

In response to this rapid rise, the body produces a lot of insulin which causes a rapid drop in blood sugar levels, leading to a sugar crash.

Studies of diabetic patients have shown that the blood sugar fluctuations may contribute to depression and mood disorders.

Hypoglycemia (low blood sugar) has also been linked with documented cases of violent outbursts, though studies on sugar consumption and behavior have produced conflicting results.

Scott Olson/Getty Images

• Partially Hydrogenated Fats

There is a growing body of evidence suggesting that partially hydrogenated fats—trans unsaturated fats—are actually causing more harm than saturated fats.

Trans fats are a common ingredient in fried and highly processed foods to improve its taste, texture, and durability. It is also present in vegetable shortening, margarine, and many others.

Cells are the smallest unit of life. Like all cells, human cells are surrounded by a double-layered membrane that is mostly composed of fat. This fat maintains the fluidity and integrity of human cells and is imperative to the health of our bodies.

Natural fat and lipids are either completely saturated, with stiff and straight tails, or cis unsaturated, meaning it will have bends in its tail, and therefore introduces fluidity when incorporated into cell membranes.

Trans unsaturated fats are unnatural in that they are partially hydrogenated (adding hydrogen atoms to the fatty chain). Like saturated fats, their chains are straight and rigid, but also has double bonds like cis unsaturated fats. Studies have shown that trans fat causes problems in brain neurons when incorporated into their membranes.

In particular, this kind of fat reduces the ability for neurons to communicate and reduces serotonin messaging. Studies have demonstrated that high trans fat consumption is linked with poor memory in middle-aged men.

A 2012 study analyzed dietary information and behavioral assessments of 945 men and women on their dietary trans fatty acids and aggression or irritability. 

Out of other factors, including old age, alcohol use, smoking, being male and education, trans fatty acid was the only factor that had a strong association with overt aggression, history of aggression, conflicts, irritability, impatience, and aggression.

Nutrient Deficiencies

Deficiencies in micronutrients include vitamins (both water- and fat-soluble), macro minerals, and micro minerals result in unbalanced homeostasis within the human body, resulting in a myriad of health conditions.

Though micronutrients are needed in much lower quantities than carbohydrates, fats, and proteins, deficiencies in micronutrients can also induce mood disorders and aggression.

Macro minerals are minerals that are needed in relatively large quantities, approximately 100mg a day. Macro minerals include calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Micro minerals are needed in lower quantities and include iron, manganese, copper, iodine, zinc, cobalt, fluoride, and selenium.

Additionally, vitamins such as vitamins A, D, E, and K (fat soluble), and folate, thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, B12, and C (water-soluble) are also needed to enable fundamental biochemical processes.

Deficiencies in any of these micronutrients will result in health problems. Some deficiencies have been documented to be associated with mood disorders.

Deficiencies in vitamin D have been linked with anger, anxiety, and depression in children. Babies born to deficient mothers have a higher chance of developing schizophrenia, and learning and cognitive disabilities.

Over 40 percent of the American population is deficient in vitamin D—also known as calciferol—the only vitamin that can be produced by the body in response to sunlight.

The active form of vitamin D is a neuroprotective hormone that is produced in the kidneys. Apart from its role in maintaining bone health, it is also present in the brain and regulates the release of chemicals that promote neural growth. It also helps mitochondrial action by reducing oxidative stress which can cause damage and death to neurons.

Sunlight, a major source for vitamin D, has been shown to regulate serotonin levels in the brain, with some studies showing that it increases serotonin release in the brain. Further, studies conducted in countries that have distinct climates throughout the seasons often find that feelings of depression increase during the winter due to reduced sun exposure.

It is recommended to get up to 30 minutes of sun exposure during midday several times a week for sufficient vitamin D production. The length of exposure can vary depending on the fairness of the skin.

Deficiencies in cobalamin, also known as vitamin B12, have been documented to cause mood disorders, dementia, paranoid psychosis, violent behavior, and fatigue. This vitamin is commonly found in eggs, poultry, fish, dairy, and red meat.

Cobalamin is a cofactor—a chemical compound that binds to other proteins to enable its action—and activates the production of dopamine and serotonin neurotransmitters with its binding action.

Therefore, deficiencies in cobalamin reduce dopamine and serotonin release, leading to potential mood disorders.

This list of nutrient deficiencies is not exhaustive. Meeting daily nutrient needs for a single vitamin or mineral is also not a silver bullet for improving mood and mental wellbeing.

However, a well-rounded and balanced diet that meets all of the vitamin and mineral needs are necessary for maximal benefit in homeostasis and mental wellbeing.

Environmental Factors

Studies into factors in the environment have also linked environmental factors with aggression and rising crime rates.

• Heat and Crime

Cities in hot areas, and hot days have been linked with increased crime and violence. This is because hot temperatures cause imbalances in our body’s homeostasis—the balance needed to stay within certain checkpoints—and can cause increased arousal in the form of increased heart rate and blood pressure, sweating of the skin, and heavy respiration.

This high arousal makes individuals more susceptible to anger and irritation, which may lead to impulsive behaviors and violence.

• Glyphosate and Autism

The relationship between autism and violence and aggression is well established within the scientific literature. Around 68 percent of autistic children and teenagers have been aggressive to a caregiver, and around half—49 percent—had also been aggressive to someone else.

There is growing evidence suggesting that there is an association with the increased use of glyphosate—the main ingredient in the herbicide Roundup—with the growing epidemic of autism in the United States.

Though correlation is not causation, Dr. Stephanie Seneff, a senior researcher from the Massachusetts Institute of Technology, suggests that glyphosate usage at least plays a factor in the autism epidemic.

Glyphosate is the most popular herbicide in the world; studies have shown that glyphosate constituted around 72 percent of all herbicides used globally between 1974 and 2014.

Studies on pregnant mothers have shown that exposure to agricultural herbicides induces neurotoxicity and increases the likelihood of giving birth to a baby with delayed cognitive development and autism.

Experiments on glyphosate exposure in mice have found that it is toxic to their neurons. Glyphosate reduces maturation of mouse neurons and reduces production of nerve branches (dendrites) which act as contact points to receive signals from other neurons. Reduced branches in neurons are also seen in people with autism.

Further, glyphosate is very similar in structure to glycine, an amino acid essential in the formation of many proteins. Therefore, Seneff speculates that during protein synthesis, cells can mistake glyphosate for glycine and incorporate it into proteins in the place of glycine.

Glycine increases glutamate signaling in neurons. Glutamate is a major excitatory neurotransmitter. However, over activation of glutamate signaling can be excitotoxic, causing neuronal stress and death.

Glyphosate has also been shown to cause excitotoxic signaling of glutamate in neurons of fetal rats. This has been shown to cause symptoms of depression and anxiety in the rats.

The herbicide’s extensive use in agriculture poses concerns. Glyphosate is heavily sprayed on genetically modified foods (GMO) that have been genetically changed to not be sensitized to glyphosate.

Such plants include soybeans, corn, and cotton, among others. Glyphosate usage in GMO plants has led to increased glyphosate-resistance in weeds.

This has prompted a negative cycle where farmers will have to use more glyphosate to control the weeds, these weeds will become even more resistant, prompting further increased use of the chemical. Since GMO plants are not sensitive to glyphosate, to increase efficiency, farmers will often spray the whole crop indiscriminately, leading to higher glyphosate content in GMO foods.

Numstocker/Shutterstock

Vaccinations

While most vaccinations are generally safe for use with relatively low risks of side effects, some peer-reviewed studies have linked neuropsychiatric disorders and brain diseases with various vaccines.

In 2017, a study led by researchers from Yale University found that children who were diagnosed with anorexia nervosa (AN), obsessive-compulsive disorder (OCD), and anxiety from 2002 to 2007 were temporally linked with influenza vaccines that had been administered 3 to 12 months prior.

The study found hepatitis vaccines were also associated with later OCD and AN diagnoses.

The researchers speculated that the vaccine and the onset of OCD and AN may have been due to abnormal immune functioning, but did not conclude if the vaccine played a part in the immune response.

Further, there have also been increased reports of psychosis following administration of COVID-19 mRNA and adenovirus (DNA) vaccines.

Many studies across the United States, India, and Saudi Arabia, among others have found that young to middle-aged adults with no previous history of psychosis or mental disorders are presenting to emergency departments with symptoms of agitation, irritability, decreased sleep, hallucinations, often within a few days following vaccination.

Emergent cases of rapid Creutzfeldt Jakob diseases (CJD) following COVID-19 vaccines have also prompted researchers’ suspicions of possible links between cognitive and brain degenerating diseases and COVID-19 vaccines, especially mRNA vaccines.

Researchers such as Dr. Stephanie Seneff, Dr. Robert Malone, Dr. Jean-Claude Perez, and the late Nobel laureate Prof. Luc Montagnier all published papers suspecting a link between mRNA COVID-19 vaccines and future development of incurable prion and prion-like diseases including CJD, Alzheimer’s, Parkinson’s disease, and amyotrophic lateral sclerosis.

Patients with these diseases all develop either cognitive or physical decline, or both. Progression of such diseases can lead to aggressive outbursts as cognitive control declines.

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