Last week, we saw how our ingrained fear response can occasionally lead us to feel threatened and anxious even when we are objectively safe. But these fear responses are also incredibly important survival mechanisms that can keep us alive and kicking in terrifying and dangerous circumstances. Many people who go through extreme traumas retain only fragmented and distorted memories of the actual traumatic event. This memory loss occurs because the brain shuts down the areas responsible for careful thought and processing, which can distract us from reacting to the threat efficiently. Meanwhile, our bodies gear up to fight, run, or protect ourselves from harm. This body-centered, reactive fear state can be hard to immediately shake off, keeping us poised and ready for another threat even a couple days later. But usually, the fear does wear off, allowing us to return to normalcy. For a subset of people though, this fear response can continue to dog them for years, long after the threat has been eliminated. This condition, known as Post-Traumatic Stress Disorder (PTSD), can affect a person’s mental and physical wellbeing and cause major disruptions in their day-to-day life. To understand why some people develop PTSD, we need to take a closer look at the biological, psychological, and social mechanisms by which we react to and process trauma.
We’ve talked a lot about how the body responds to potential threats. Those physiological stress responses are driven by instinctual processing in the brain and the autonomic nervous system. It may seem simple—the brain detects a threat and triggers the body to defend itself in whatever way it can. But that initial physical response is only a tiny fraction of how the brain processes trauma. There’s a lot we still don’t know about how trauma impacts the brain. For example, we know that traumatic events are often difficult to completely remember, but that’s not nearly the whole picture. People who experience trauma, particularly those with PTSD, actually tend to have a strong sensory memory of the traumatic event. These memories can be jumbled and lack narrative structure, and they are often focused on the source of the threat. This makes sense—when you’re in a dangerous situation, you want to hold onto details that can help you escape and let go of anything irrelevant. The resulting memories are richly detailed but scattered and disorganized—as if your brain tried to throw them together in a hurry. Afterward, your brain holds onto all of these visceral memories, but it can’t put them back together into a coherent story.
The effect of trauma on memory is a major driver of PTSD. In fact, one of the biggest signs of PTSD is recurrent and intrusive memories of the trauma. Intrusive memories come in the form of persistent thoughts about the trauma, nightmares in which the trauma is re-experienced, and intensely realistic flashbacks—often triggered by sensory details of the trauma. There are a lot of competing theories about how traumatic memories influence the development of PTSD. Some people argue that a preexisting deficit in the way we store and process memories increases the risk of having PTSD after a trauma. Biological factors like genetics and the structure of the brain—particularly the hippocampus where memories are stored—have been linked with increased risk of PTSD. Alternatively, there is evidence that the cognitive effects of PTSD contribute to the degradation of memory, particularly the diminished ability to form new memories.
Either way, disorganized memory plays an important role in the persistence of trauma. The intrusive memories associated with PTSD are really just side effects of the brain trying to process and understand memories it cannot completely reconstruct. The traumatic event acts like a corrupted file that the processors can’t resolve, so the brain keeps trying to compile that memory and file it away with little success. Because of this relationship between trauma and memory, an effective way to treat PTSD can be through memory reconsolidation. This technique involves purposefully reconstructing the corrupted memory and overwriting it with a “clean copy.” It may seem counterintuitive, but recalling the memory and rebuilding the narrative structure of the traumatic event can help the brain file it away more effectively.
Intrusive memories aren’t the only symptoms of PTSD. Similar to other anxiety disorders, the fear associated with PTSD can cause people to avoid objects and activities that their brains may perceive as threats. For people with PTSD, this can mean avoiding specific flashback triggers or avoiding thinking about or processing the trauma. But because intrusive memories are internal and often difficult to predict, avoidance can also mean using drugs or alcohol to suppress the brain. Roughly 40% of people with PTSD also struggle with a substance addiction, which only makes processing and recovering from the trauma more difficult. People with PTSD can also experience symptoms of dissociation—feelings of being disconnected from your body, disoriented, or confused—which the brain uses to avoid processing the trauma memories.
The last two broad categories of PTSD symptoms are restless hyperactivity and dysregulated mood. Intrusive memories can keep people with PTSD in an ongoing fear state that can create a sense of anxiety and hypervigilance. When the fear dissipates, depleted resources in the brain and negative thoughts can contribute to feelings of depression. These symptoms can be managed with medications like antidepressants and mood stabilizers, but they cannot be fully eliminated until the underlying trauma is addressed through therapy. Interestingly, there is recent evidence suggesting that the psychoactive drug MDMA (colloquially known as ecstasy), paired with professional therapy, can be an effective treatment for PTSD. The drug seems to significantly dampen the brain’s automatic fear response, giving people with PTSD the space to process and reconsolidate traumatic memories. A lot more research needs to be done, but treatments like this could be a breakthrough for those with PTSD who aren’t able to process the trauma with therapy alone.
For more information on mental health, check out the resources on the NAMI website. Science You Can Bring Home To Mom will be back in two weeks with a brand new science series! For now, check out last month’s series on the psychology of perception and cognition. Comment on this post or email me at contact@anyonecanscience.com to let me know what you think about this week’s blog post and tell me what sorts of topics you want me to cover in the future. And subscribe below for weekly science posts sent straight to your email!
National Suicide Prevention Lifeline:
- 800-273-8255 (24/7)
- Online chat: https://suicidepreventionlifeline.org/chat/ (24/7)
- https://suicidepreventionlifeline.org/
For International Suicide Resources: https://www.opencounseling.com/suicide-hotlines
