The Consequences of Childhood Abuse Last Until Adulthood: What are the Implications for Society?

(© Derek Simon 2015)
(© Derek Simon 2015)

One of the great questions in the addiction field is why do some people become full-blown addicts while other people can use drugs occasionally without progressing to anything more serious? One part the answer definitely has to do with the drug itself. For example, heroin causes a more intensely pleasurable high than cocaine and people that try heroin are more likely to become addicted to it than cocaine. But that’s not the whole story.

I’ve written previously about how a negative, stressful environment can have long-lasting negative impacts on the development of a child’s brain (also known as early-life stress of ELS). ELS such as childhood abuse (physical or sexual) and neglect can increase the risk for a whole host of problems as an adult such as depression, bipolar disorder, PTSD, and of course drug and alcohol abuse. There’s even a risk for more physical ailments like obesity, migraines, cardiovascular disease, diabetes, and more.

Childhood abuse/neglect = psychological and physical problems as an adult.

Attitudes towards childhood development have certainly changed! Child coal miners ca. 1911 (
Attitudes towards childhood development have certainly changed! Child coal miners ca. 1911 (

This idea doesn’t sound too controversial but believe it or not, the idea that a bad or stressful situation as a child would do anything to you as an adult was laughed away as not possible. It’s only within the last decade or so that a wealth of research has supported this idea that ELS can physically change the brain and that these changes can last through the abused child’s entire life.

This recent review paper (published in the journal Neuron) is an excellent, albeit technical, summary of dozens research papers done on this subject and the underlying biology behind their findings.

Paradise lost childhood abuse review 2016 title

I especially love the quotes the author included at the beginning of the article:

Paradise lost childhood abuse review 2016 quotes

And even more recently, yet another research paper has come out that highlights how important childhood is for the development of the brain and how a stressful childhood environment can impact the function of a person as an adult.

Childhood abuse paper 2016

This most recent report, published in the journal Neuropscyhopharmacology concludes that early childhood abuse affects male and females differently. That is to say that the physical changes that occur in the brain are distinct for men and women who were abused as children.

Studies like this one are done by examining the brains of adults who were abused as kids and then comparing the activity or structure of different parts of the brain to the brains of adults who were not abused. The general technique of examining the structure or activity of the brain in a living human being is called neuroimaging and includes a range of techniques such as MRI, PET, fMRI, and others. (I’ve written about some of these techniques before. In fact, the development of better methods to image the brain is a huge are of research in the neuroscience field).

However, this study did not examine behavioral differences in the subjects, but as I said above, a great number of many other studies have looked at the psychological consequences of ELS. But this paper is really primarily interested in the gender differences in the brains of adults that have been abused as kids.

*Note: the following discussion is entirely my own and is not mentioned or alluded to by the author’s of this study at all.

This work—and the many studies that preceded it—has important implications because as a society, we have to realize that part of our personality/intelligence/character/etc. is determined by our genetics while the other part totally depends on the environment we are born into. I don’t want to extrapolate too much but the idea that childhood abuse can increase the risk of psychological problems as an adult also supports the broader notion that a great deal of a person’s success is determined by entirely random circumstances.

The Adverse Consequences Pyramid perfectly illustrates how ELS/abuse/neglect (the bottom of the pyramid) leads to much greater problems in later life. (

The science shows that a child born into a household rife with abuse will have more chance of suffering from a psychological problem (such as addiction) as an adult than someone who was born into a more stable life. The psychological problem could hurt that person’s ability to study in school or to hold down a job. And the tragic irony, of course, is that no child gets to choose the conditions under which they are born. A child, born completely without a choice of any kind over whether or not he or she will be abused, can still suffer the consequences of it (and blame for it) as an adult.

As a society, we often always blame a person’s failures as brought on by his or her own personal failings, but what if a person’s childhood plays an important role in why that person might have failed? How, as a society, do we incorporate this information into the idea of ourselves as having complete control over our minds and our destinies, when we very clearly do not? As an adult, how much of a person’s personality is really “their own problem” when research like this clearly show that ELS impacts a person well after the abuse has ended?

If the environment a child is born into has a tangible, physical effect on how the brain functions as an adult, than this problem is more than a social or an economic one: this is a matter of public health. Studies that support findings such as these provide empirical significance for public policy and public services for child care such as universal pre-K, increased availability of daycare, health insurance/medical access for children, increased and equitable funding for all public schools regardless of the economic situation of the district that school happens to be located in, etc.

One of our goals as a society (if indeed we believe ourselves to be a functioning society…the success of Donald Trump’s candidacy raises some serious doubts…but I digress) is the improvement of the lives of ALL of our citizens and securing the prosperity of the society for future generations. Reducing childhood poverty and abuse quite literally could help secure the future generations themselves and improve the ability of any child to grow up to become a successful and productive adult.

Public programs are essential because the unfortunate reality for many people born into poverty is that they must work all the time at low paying jobs in order to simply survive and may not be able to give their children all the advantages of a wealthier family. And this is where government and public policy step in, to correct the imbalances and unfairness inherent to the randomness of life and level the playing field for all peoples. Of course, the specific programs and policies to reduce childhood poverty and abuse would need to be evaluated empirically themselves to guarantee an important improvement in development of the brain and health of the child when he/she grows up.

And this is the real power of neuroscience and basic scientific research papers like this one. Research into how our brains operate in real-life situations reveal a side of our minds and our personalities that we never may have considered before and the huge implications this can have for society. The brain is a complex machine and just like other machines it can be broken.

Of course, we shouldn’t extrapolate too much and say that, for example, a drug addict who was abused as a child is not responsible for anything they’ve ever done in between. But is important to recognize all the mitigating factors at play in a person’s success and simply dismiss someone’s problems as “their own personal responsibility.” As a neuroscientist, I might argue that that phrase and the issues behind it are way more nuanced than the how certain politicians like to use it.

Special endnote Due to some recent shifts in my career, Dr. Simon Says Science will be expanding the content that I write about. Addiction and neuroscience will still be prominently featured but I plan to delve into a variety of other topics that I find interesting and sharing opinions that I think are important. I hope you will enjoy the changes! Thanks very much!



The Formation of New Memories in the Human Brain

Image of the structure of the mouse Hippocampus (Image courtesy of
Image of the structure of the mouse Hippocampus (Image courtesy of

How are new memories created?

This is a fascinating question in neuroscience and at the very core of what makes us human. After all, our entire concept of ourselves is defined by our memories and without them, are we even ourselves? This is a pretty lofty philosophical discussion… but today we’re only interested in the neuroscience of memory.

In specific, what happens to individual neurons in the human brain when a new memory is created and recalled?

Researchers at the University of California-Los Angeles performed a study in humans that has shed some light on this important question. Published recently in the journal Neuron, the novelty of the study involved recording how many times a neuron would fire during a specially designed memory test. In other words, the scientists were able to monitor what happened to individual neurons in a human being as a new memory was being created!

Title Ison et al. 2015

This article is open access (able to downloaded and distributed for free). The article can be found here or download the pdf.

Before I go into what the researchers found, let’s see how it was done.

The subjects in the study were patients being treated for epilepsy. As part of their clinical diagnosis, they had been implanted with an electrode, a tool used to measure neuronal activity or in other words, the electrode measures how often a neuron fires. The fact these patients already had an electrode inserted into the brain for clinical reasons made it convenient for the researchers to conduct this study.

Left Temporal Lobe (
Left Temporal Lobe (

The brain region in which the electrode was implanted is called the medial temporal lobe (MTL). The image to the right is of the left human temporal lobe. The medial region of the temporal lobe is located more towards the center of the brain.

Human Hippocampus (
Human Hippocampus (

One specific region of the MTL, the hippocampus, is believed to be the primary brain region where memories are “stored”. Specifically, previous studies in animals and humans have suggested that the MTL and hippocampus are very important to encoding episodic memory. Episodic memory involves memories about specific events or places. In this study, the example of episodic memory being used is remembering seeing a person at a particular place. Another example: the game Simon™ can be considered a test of your brain’s ability to rapidly create and recall short-term episodic memories!

Simon game memory

*Note: Episodic memory is considered one of the main bifurcations of declarative memory, or memories that can be consciously recalled. The other type of declarative memory is semantic memory, which are memories of non-physical/tangible things, like facts.

To test the episodic memory of remembering a person at a particular place, images were presented to the patients while the neurons were being recorded. There were 5 different tasks (all completed within 25-30min). See Figure 1 below from the paper.

Figure 1: Experimental Design
Figure 1: Experimental Design

First, a pre-screening was done in which the patients was shown many random images of people and places. The activity of multiple neurons was recorded and the data was quickly analyzed then 3-8 pairs of images were compiled. In each pair, 1 image was “preferred” or “P” image, meaning the neurons being recorded fired when the “P” image was shown. The second image was “non-preferred” or “NP” image, meaning the neurons did not respond to it when it was shown.

The first task is the “Screening” test. Each “P” and “NP” image was shown individually and the neurons response to each was recorded. As you would expect, the neuron would fire heavily to the “P” image and not very much to the “NP” image.

The second task was the “learning task” in which a composite image of each of the “P” and “NP” image pairs was made. The person in the “P” image was digitally extracted and placed in front of the landmark in the “NP” image. After the composite images were shown, the individual images were shown again.

For example, in one image pair for one patient, the “P” image was a member of the patient’s family while the “NP” image was the Eiffel Tower (for this example, see Figure 2). The composite image in the “learning” task was the family member in front of the Eiffel Tower. Another example of a “P” image was Clint Eastwood and the “NP” image was the Hollywood sign. The composite image would therefore be Clint Eastwood in front of the Hollywood sign. (However, in some image pairs the “P” image was a place and “NP” image was a person).

The third task was “assessing learning”. The image of just the person in the composite image was shown and the patient had to pick out the correct landmark he/she was paired with. For example, the picture of the family member was shown and the patient would have to pick out the Eiffel Tower image.

The fourth task was the “recall” task. The landmark image was shown and the patient had to remember and say the person it was paired with. For example, the Eiffel Tower was shown and the patient had to say the family member’s name.

Finally, the fifth task was a “re-screening” in which each individual image was shown again so the neuron’s activity could be compared to the Task 1, pre-learning.

The activity of multiple neurons were recorded for each image for each of the tasks. The data was then analyzed in number of different ways and the activity of different neurons was reported.

And what was found?

Figure 2: Response of Neruons in the Hippocampus from One Patient
Figure 2: Response of Neurons in the Hippocampus from a Patient

Let’s go back to the family member/Eiffel tower example. The researchers were able to show that a neuron in the hippocampus responded heavily to the picture of the family member (“P” image) but not to the Eiffel Tower (“NP” image). After showing the composite image, the neuron now responded to the Eiffel Tower too in addition to the family member! (The neuron also fired a comparable amount to the individual family member image as the composite image).

As you can see in Figure 2, each little red or blue line indicates when a neuron fired. For example, in Task 1 you can clearly see more firing (more lines) to the “P” image than the “NP” image. You can see that after Task 2, the neuron responds to either the “P” or “NP” image (especially obvious in the Task 5). The middle graph indicates the firing rate of the neurons to the “NP” image and it clearly shows increased firing rate of the neuron after learning (AL) compared to before learning (BL). It may look small, but the scientists calculated a 230% increase in firing rate of the neuron to “NP” image after the learning/memory task took place!

What does this mean? It means that a new episodic memory has been created and a single neuron is now firing in a new pattern in order to help encode the new memory!

This was confirmed the other way around too. In another patient, the “P” neuron was the White House and the “NP” image was beach volleyball player Kerry Walsh. The neuron that was being recorded fired a lot when the image of the White House was shown but not so much for the Kerri Walsh image. Then the composite image was shown and the learning/recall tasks were performed. The neuron was shown to fire to both the White House image AND the Kerry Walsh image! The neuron was responding to the new association memory that was created!

Keep in mind these are just two examples. The scientists actually recorded from ~600 neurons in several different brain regions besides the hippocampus but they only used about 50 of them that responded to visual presentation of the “P” image, either a person or a landmark (the identification of visually responsive neurons was crucial part of the experiment). Remarkably, when the firing rates of all these neurons was averaged before and after the memory/learning tasks, a similar finding to the above examples was found: the neuron now responded to the “NP” image after the composite was shown!

Many other statistical analyses of the data was done to prove this was not just a fluke of one or two neurons but was consistent observation amongst all the neurons studied but I won’t go into those details now.

But what’s going on here? Are the neurons that respond to the “P” stimulus now directly responding to the “NP” image or is more indirect, some other neuron is responding to the “NP” which in turn signals to the “P” neuron to increase in firing? The authors performed some interesting analyses that both of these mechanisms may apply but for different neurons.

Finally, were all the recorded neurons that were engaged in encoding the new episodic memory located in the hippocampus? The answer is no. Responsive neurons were identified in several brain regions besides the hippocampus including the entorhinal cortex and the amygdala. But most of the responsive cells were located within the parahippocampal cortex, a region of the cortex that surrounds the hippocampus, thus not surprising it is very involved in encoding a new memory.

In conclusion, the scientists were able to observe for the first time the creation of a new memory in the human brain at the level of a single neuron. This is an important development but such a detailed analysis has never before been done in humans and, most importantly, in real time. Meaning, the experiment was able to observe the actual inception of a new memory at the neuronal level.

However, one major limitation is that the activity of these neurons were not studied in the long term so it’s unknown if the rapid change in activity is a short-term response to the association of the two images or if it really represents a long-term memory. The authors acknowledge this limitation but the problem is really in the difficulty of doing such studies in humans. It’s not really ethical to leave an electrode in someone’s brain just so that you can test them every week!

But what does all of this mean? The authors do suggest that the work may help to resolve a debate that has been going in on the psychology field since the 40s. Do associations form gradually or rapidly? These results strongly suggest new neurons rapidly respond to encode the new memory formation.

But how will these results shape the neuroscience of memory? The answer is I don’t know and no one does. Thus is the rich tapestry of neuroscience, another thread weaved by the continuing work of scientists all over the world  in order to understand what it is that makes us human: our brains.

Drug Addiction is a Medical Disease-a Disease of the Brain

brain1 med symbol good

Let me say that again, Drug Addiction is a medical disease-a disease of the brain.

To some people, this may sound controversial but throughout my posts I hope to provide the scientific explanation for why this is and how we know that this is true. Drug addiction is a very complex disease and a great deal of knowledge is required to understand it.

But what is addiction? The textbook definition of addiction (according to Wikipedia) is “a state characterized by compulsive engagement in rewarding stimuli, despite adverse consequences”. “Rewarding stimuli” can be food, sex, gambling, the Internet, or in our case, drugs of abuse. And as we’ll learn later, all these “rewarding stimuli” hijack the brain in very similar (yet distinct) ways. “Adverse consequences” can be anything from losing your job to deterioration of your health to committing a crime.

Historically, a drug addict was considered someone that was weak, lacked a strong will, or was morally inferior. This is not true.


Drugs of abuse (nicotine, cocaine, marijuana, alcohol, heroin, oxycodone, etc.) are not magic: they are physical substances that have a physical effect, specifically on the brain. The function of an addict’s brain has been changed as a result of the drug use; their behaviors and motivations—even what you might call their “will—have changed (more on this later). An addict is not “morally weak” but suffering from an illness of the brain and, in many instances, in need of compassion and help.

A quick note:

I must point out that a person cannot even become a drug addict unless they try the drug in the first place. But the reasons behind this first use are complicated with numerous contributing factors to consider: sociology, public policy, genetic predisposition, environment, and many other issues. Ridiculous simplifications such as “just say no” or absurd taglines like “the war on drugs” don’t even begin to address the problem. More on this in future posts.

Another quick note: This post is a bit long but I will try to keep future ones a more reasonable length.

Now, back to the neuroscience:

By now, some of the questions you should be asking are: how do we know that addiction is a medical disease/brain disease? How do drugs act on the brain and what do we even mean that brain function is “changed”? And even if drugs do change the brain, how does this translate into changed behavior, such as uncontrollable drug craving, or bad behavior/“adverse consequences”?

So we all know that our body is made up of organs: heart, lungs, intestines, etc. and those organs are responsible for carrying out different jobs that keep us alive (blood circulation, breathing, food digestion and absorption, etc.). The brain is an organ just like any other with specific jobs to do.

We were taught since we were young that the brain is the control center of the body, which is  one of those phrases that is technically true but doesn’t really offer much real insight. By control center, we mean that the brain controls, regulates, and coordinates how our organs function (breathing, heart rate, muscle movement, etc.). Less well understood is that the brain also controls our behaviors, actions, thoughts, and emotions—our minds.

Let me phrase that in a different way, the result of the brain’s functions IS the mind!Brain-=-Mind

This may be controversial to some and at the neuroscientific level, is remarkably complex and not very intuitive. The brain vs mind topic will be a primary theme this blog will cover.

But let’s just assume for a moment that I’m correct and our thoughts and behaviors come from the biological functions of the brain. Then if something changes how the brain operates (like an illegal drug, for example), then it stands to reason our thoughts and behaviors would also be changed. If this change is harmful and results in negative behaviors or thoughts, you could think of the brain as suffering from a disease.

Let’s consider this in slightly more detail by thinking about disease more generally.

You may or may not have thought about this in this way, but the entire modern medical profession is based on a standard way of treating illness: the medical model of disease. The model is simple to understand: illness occurs because something (bacteria, virus, a genetic mutation, a poison, etc.) affects a particular organ, causing it to not work properly and resulting in the symptoms of the disease. Therefore, if you eliminate the cause of, or reverse, the damage to the organ,  you ameliorate the symptoms and cure the disease.

The figure below compares three different diseases in the context of the disease model: cystic fibrosis, hepatitis, and drug addiction.


For cystic fibrosis, the cause of the disease is a genetic mutation that you inherit from your parents. The organ the mutation affects is the lung. The mutation causes the lungs to produce more mucous which makes breathing more difficult (the symptoms).

For hepatitis, a virus, the hepatitis virus, causes the disease. The virus specifically infects the liver (the affected organ), which it damages and causes a loss of appetite and malaise, can lead to yellow discoloration of the skin, or more severe liver damage (the symptoms).

For drug addiction, the cause of the disease is drug abuse. The drugs act on brain cells (neurons) which changes how they work. The change in brain function results in the drug-specific effects that you experience right away, while repeated use results in cravings, drug-seeking behavior, and even withdrawals (all of these are symptoms).

However, unlike the other diseases, the symptoms of cystic fibrosis or hepatitis do not feedback onto the organ to worsen the effects of the initial cause. But for drug addiction, this is exactly what happens. Drug addiction operates in a cycle in which the symptoms promote the cause (more on this in the future).

And one more significant caveat, not everyone that tries a drug will become an addict. This is just another layer of complexity that will be discussed in more detail later.

But so far, I haven’t discussed any concrete neuroscience. I’ve kept things very vague with phrases like “changes in brain function” but what changes am I talking about? Specifically, drugs change how brain cells, called neurons, talk to one another.

OK, that’s plenty for a little introduction…

Next Post

Introduction to Neuroscience: the Neuron.