Dark Side: Neurotransmitters

There were cases where the murderer denied early abuse, but many people will deny such abuse, only for it to be discovered later that either they were too embarrassed to admit it, or they were protecting  the abusing adult, typically a family member. It was also becoming known from many studies that there was a high incidence of early childhood physical, emotional, or sexual abuse in the prison population of psychopaths. A small survey of thirty-five psychopathic offenders in youth detention facilities found that 70 percent reported serious mistreatment throughout childhood. Given that the onset of reliable memory for childhood events in adults may reach back to three to four years of age, this implied that a higher percentage of adult criminal psychopaths actually experienced significant abuse earlier than that. As such, it was possible that more than 90 percent of them were abused at some point in their early life. Add to this those psychopaths who protect their abusers, and the percentage could approach 99 percent.

 

The environment can interact with genes during development in a number of ways. One of those is through what’s called a genotype-environment correlation. A child with genes predisposing him to aggression may frequently misbehave, drawing hostility and abuse from his caretaker. Or an aggressive parent may pass along genes for hostility and also behave in a belligerent way toward his kids, and then both the genes and the antisocial attitude continue down the line. Such a pattern could explain any murderous lines of ancestors. Even if genes for aggression washed out over the generations, an expectation that families always act like this could have remained.

 

Another form of gene-environment interaction is what’s known as epigenetic marking. Seemingly out of nowhere, your teenage daughter, who doesn’t have the svelte shape of you or even your mother, starts to put on weight and looks very much like your grandmother, her great-grandmother. To figure out why, you all decide to take standard DNA tests to determine your respective genetic codes. But it turns out that the DNA code controlling the appetite and obesity of your plumping daughter is more similar to the DNA code of yourself your lean mother than to that of your fleshy grandmother. So the genetics don’t seem to explain your daughter’s teenage-onset obesity. And she doesn’t eat much more than an average person. Something else unexpected must be going on. Perhaps her metabolism is malfunctioning. But how and why? Then your niece, who is studying genetics in her doctoral work, suggests something may have been passed down from great-grandmother to grandmother to you, and then to your daughter. That something is not the genetic code itself, but a small extra bit, or tag, of chemical information stuck on to several genes controlling obesity and metabolism.

 

The study called an epigenetic tag, might have been added on to several of her great-grandmother’s genes while she was a young child, enduring starvation during a decade-long famine in Ireland, Poland, Bosnia, or the Bronx, nearly a century ago. Her great-grandmother’s cellular response to the great stresses of that starvation may have been to change her metabolic machinery to more efficiently use energy and store fat, and to increase appetite once food was plentiful again. So your daughter, her great-granddaughter, under other teenage stressors, and with a plentiful food supply, responded by putting on weight to the point where she now resembles the plump but hearty teenager her great-grandmother became when the famine ended in her homeland eighty years ago. Some of these effects are dependent on whether the ancestor was male or female, since certain genes are “imprinted” on either the paternal or maternal side of the family.

 

The epigenetic tag is one of many alterations to the genetic code that can be induced by environmental stressors. This is one of the core mechanisms underlying the interaction of nature and nurture. While there have been numerous recent studies on the role of epigenetic interactions on metabolism, cancer, and susceptibility to infectious and immune diseases, it is also a key to understanding some psychiatric disorders, from schizophrenia to psychopathy.

 

The raw DNA base pair code in this analogy is “thatthatisisthatthat,” and the way this raw sequence is laid out directs the code to be transcribed into the sequence of words but not quite a sentence. Normally the transcribed message from the DNA to the RNA would be translated into the protein, here the mature and sensical sentences “That that is, is. That that is not, is not. Is that it? It is.” But environmental stressors can induce epigenetic tags to be added on to some of the original genetic DNA, so that the punctuation, the spacing of the words, the text formatting in general, can be altered to produce a slightly different meaning: “That that is, is. That that is not, is not. Is that it? It is?” Same words, same sequence, but a final question mark added changes the thrust of the message. This slight “epigenetic” change to the sentence’s intended “genetic” meaning is different from an actual mutation. In a mutation, the actual spelling of the sentence is changed, either by inserting a letter (or more) or deleting an existing letter. Such a change can, of course, radically alter the function of the sentence, which may now become, “That that is, That that is not, is snot.

 

Another way of looking at the epigenome function is to consider the new car you buy from the dealer. All that original hardware is like your genome, while alterations you might make to soup it up, give it some more pep, or, for your daughter, slow it down, are like the epigenetic modifications. Epigenetic alterations are one of several reasons why identical twins are not identical. Even with identical raw genetic codes, differences in early environment, whether overly stressful or more positively enriching, can change their behaviors down the line as teenagers and adults. Identical twins can also have different numbers of the same genes inherited from one parent or another, and this can also alter how the identical twins look and behave. A third mechanism can involve a seemingly otherworldly phenomenon caused by “retrotransposons.”

 

Retrotransposons are short bits of DNA or RNA present in the nucleus of the cell surrounding the genes themselves. Once thought to be junk DNA with no apparent purpose, these odd snippets of information are not fixed in place but can move around, like grains of rice in soup. They are capable of connecting widely separate genes, even on different chromosomes, and they can alter cellular function. They can rearrange the “sentences” our DNA types out, and in doing so can ultimately change, usually subtly, human behavior, and account for not only differences in how identical twins act, but also what makes schizophrenics psychotic and perhaps why certain depressives become suicidal.

 

One of the most common ways the epigenome functions is when environmental stressors, especially early in life, wrap DNA filaments around spools of protein called histones. Stressors can also add or remove minuscule chemical side groups, called methyl and acetyl, to or from genes. These are just small groups of atoms that latch on to DNA strands. Such alterations can stop, slow down, or speed up a gene’s ability to be read and do its job. Changing a gene’s action alters the amount of proteins that are made, and therefore changes the balance of neurotransmitters in brain circuits, leading to changes in thoughts, emotions, and behaviors. These modifications are a big deal and have become a major focus in the understanding of the interaction of genes and environment, and are the key to understanding the nature-nurture problem. One of the main environmental stimuli that add these methyl and acetyl groups is stress, and these stimuli can include abuse, prenatal maternal anxiety, drugs, and even some foods. Stress releases the hormone cortisol, which transfers methyl and acetyl groups from donor molecules on to DNA.

 

Those several months following birth are sometimes called the “fourth trimester,” and this extended period of what should have been prenatal development means that early environment for a human infant is particularly important. In fact, the most vulnerable time for a human’s brain development in terms of environmental impact is from the period of birth and for several months in this fourth trimester. It is in this time that a human needs to avoid serious stressors, and it is when nurturing is so critical. 

Acknowledgements:

www.politie.nl  and a Chief Inspector – Mr. Henk van Essen© from 1th of March 2024 new Politiekorpschef  Janny Knol

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