Does emotional trauma change the brain?
"Yes, it does.
Really, any trauma can change the brain, especially when it happens in the earlier years of development. To make this as short as I can, when the mind has a lot of trauma coming at it consistently, it tends to make changes to adapt to that new unpleasant stimuli, and it can do it in a lot of ways, which can lead to disorder later on in life.
Take for instance a child that is consistently going through a barrage of emotionally traumatizing experiences as a result of a demonizing parent. As time goes on, the child and the mind try to protect themselves from hearing and feeling that negativity. One of the ways that it does that is to increase activity in certain regions of the brain where our fight/flight/freeze response is housed. When an incident comes, the mind goes to that place. Then it happens again, and it goes to that place. And again, and again, and again. Eventually, you see a pattern developing, and eventually, it doesn't have to be the emotional trauma that sends the activity to that part of the brain mentioned earlier, it can be anything that reminds the person of that emotional trauma, or as we call them, it can be a trigger. As the person-in-development spends more time in that part of the mind, the other areas become underdeveloped, and those are usually the areas that involve self-soothing, mood stabilization/regulation, self-image, and reactivity.
What happens is, these experiences cause a firing of the neurons in the brain to make a response. After time, the response becomes a behavior, when the behavior causes problems, even after the trauma is gone, we call these symptoms or remnants. But because this is now a habit, and a behavior, it has made a physiological change in the brain to respond to this unpleasant emotional trauma. This is a process known as kindling, and it is the reason why addiction is so hard to break, why things that remind/trigger us about trauma send us right back to that time in flashbacks; they are the loops that are made in the mind as a result of an action leading to a reaction. They are active until they are worked on or a new behavior is made. This explains why if a person is emotionally impacted by someone of importance telling them that they are terrible and no good, then the reaction may be that the person internalizes that and thinks that they are not a good person. If it happens over time, then they may actually believe that they are no good of a person, and in the future, when the emotionally negative person is gone, the remnants of their words still trigger the person because that behavioral response is still there in the brain. Also, anytime the person who was subjected to that emotional negativity comes into contact with a sense that reminds them of that experience, they are immediately brought to the thought “I am not a good person” - even though that is not the case, and that person that told them that is long gone.
This all comes about as a result of changes that happened in the brain physiologically, and it is the reason why treating trauma that had a significant impact on someone, really treating it, is complex and takes a lot of time. In a sense the treatment is to try and “rewire” the brain, through DBT, and other various talk therapies.
Hope this makes sense.

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Charles West. Forensic psychologist.