Even “Forgotten” Trauma May Trigger PTSD Symptoms in Adults

Michael S. Fanselow, Ph.D. - Brain and behavior expert on ptsd
Michael S. Fanselow, Ph.D.

It is well-known that the symptoms of post-traumatic stress disorder (PTSD) are precipitated by traumatic events or highly stressful experiences, including events that happened early in life. New research from a team led by a NARSAD Distinguished Investigator Grantee adds a surprising new dimension to this. They have found that it may not be necessary for one to explicitly remember a stressful or traumatic event for it to cause PTSD.

Michael S. Fanselow, Ph.D., of the University of California, Los Angeles (UCLA), a 2011 NARSAD Distinguished Investigator Grantee, and colleagues reported August 15th in Biological Psychiatry that an adult suffering PTSD symptoms may have no recollection of any childhood trauma whatsoever if the trauma occurred during a period early in life before the brain is wired to recall memories.

The new finding does not pertain to the often debilitating PTSD symptom of flashbacks brought on by cues in the environment linked to an original trauma. To have a flashback, one has to have a memory of the event, which often includes such details as odors, sounds, time of day and place.  

Dr. Fanselow’s team conducted experiments in very young rats—animals 19 days old, at a stage of development just before the rat brain becomes able to form “explicit memories,” or those that can be voluntarily recalled and described. These juveniles were exposed to a single session of unpredictable stress (foot shocks). Then, after maturing to adulthood, they tested the animals for their memory of the event and also measured their fear response.

The researchers treated a part of the animals’ cages with a pungent odor during the stressful experience to serve as a later cue for the event. The rats did not show evidence of remembering the stress or the environment in which it occurred. “But they did show a persistent increase in anxiety-related behavior and increased learning of new fear situations,” said team member Andrew Poulos, Ph.D., of UCLA. One of the anxieties noted was a mild aversion to the odor associated with their stress. In people with PTSD and vivid fear memories, such sensory cues can be quite severe.

In related experiments, Dr. Fanselow’s team noted other irregularities in the adult rats that had experienced early-life stress. The daily rhythms of the stress hormone corticosterone in their systems was altered––they had more “docking ports,” or cellular receptors, for this hormone in neurons of the amygdala, a known fear center. In future experiments, the team will try to determine if it is indeed the greater availability of such receptors—and/or the shifts in hormone levels during the day—that cause the increased fear and anxiety.

"These data highlight the importance of the many ways in which the brain processes traumatic experiences,” commented Foundation Scientific Council member John H. Krystal, M.D., Editor of Biological Psychiatry. “Psychotherapy tends to focus heavily on the articulation of trauma memories. However, the current study highlights that these explicit memories may not represent all brain processes that drive distress and disability. In other words, there may be a mismatch between what people think and how they feel about their traumatic experiences. Thus, there may be a role in treatment for measuring other dimensions of response, such as physiologic arousal, through which some of these other forms of learning are expressed."

Read the paper abstract.

Article comments

PTSD common in many ways and not restricted to the terror memories of war survivors. There war many kinds of war that are too difficult to comprehend, explain or accept.

This describes what has been happening to me. How do I stop it? How do I stop panicking over everything? How do I make this stop so I can be normal again? I have gone from 212 pounds to now 119. Please help me.

I was hit by a car when I was ten years old. It was a hit and run accident. My injuries were a broken leg. where I spent two months in hospital. I'm a very up tight person. Angry adult to this day.. Thoughts of suicide I get. i also use to have dreams of being dead. Very real feeling. I have anxiety attacks and fits of rage. Could I be having PTSD ?


I am not a specialist in PTSD but I'm not sure I'm not suffering from it. I self medicate. You need a professional. I believe that when one is a child (at least for me). At age 2 I picked up a stray cat in my front yard and it bit me and ran away. That trauma of the bite was nothing to me in comparison to the severe reactions of the My mom and dad and then the whole neighborhood were acting so scarey. 21/2 years old and having to try to identify dead cats because everyone was so concerned that something horrible was going to happen if I couldn't . Neighbors found a dead cat in a field about a block away. They took off it's head and took it to a Dr. It had been dead too long. The whisperings and fear on everyone's face' was far more traumatic than the actual being bit by a cat. Rabies shots, all I remember is thinking and crying to my dad, "do I have to go again" for the shots. Every day for 14 days. I don't fear cats, I never feared my dad, I don't like needles. But I smoke pot and Drink and take Valium or whatever other anti anxiety med I can get without going to a Dr. From the streets. I fear Drs. I'm just saying, it's not always the event itself as much as the reactions of those around you when your a child anyway. Who was responding to the accident and how they responded is something to think about. Especially being a hit and run. It's somewhat like being bit and run. Everyone went nuts.

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