Causes of Post Traumatic Stress Disorder

How the Brain Manages New Information

When we have a new thought or experience, our brains do not just manufacture a memory and store it in a heap in our head. We are not aware of it, but our mind categorizes every new thought and stimulus that we encounter. Our brains have certain expectations about the world, and about ourselves. These are known as schemas. A brain might contain a schema that says, “Most birds can fly, but not all”. We also have more abstract schemas relating to the world and ourselves, for example “Life is often unpleasant”, or  “I am a capable person”.

When new information enters the brain, the brain will compare this input to the schemas that it has on the topic. If the information matches an existing schema, then that schema will be strengthened. For example, you might have a bad day, and this will strengthen a schema that says, “Life is often unpleasant”.

On the other hand, information may be discarded as an isolated exception to the schema. For example, say you miss a deadline at work. If you have a schema that says, “I am a capable person”, it is unlikely that you will dwell on the incident for very long. Your brain places no significance on the event.

However, there is a third method that the brain may use. If, for example, you missed many deadlines at work, forgot your partner’s birthday and then crashed your car, you may begin to doubt that you are capable. Your brain might modify the schema to say, “I am only sometimes capable”.

How the Brain Manages Trauma

This highly simplified model of the mind helps us understand how post traumatic stress disorder might happen. When a traumatic event occurs, the brain must make sense of it within a schema. A disaster victim can no longer sustain a schema that says, “Bad things only happen to bad people”. An assault victim cannot sustain a schema that says, “Everyone is mostly good”.

The intensity of the experience means that the memory cannot be discarded as insignificant. The mind must change its existing schemas to cope with the new information, and even create new schemas to help make sense of what has happened. A sufferer of post traumatic stress disorder falters at this point.

It is thought that there are two possible routes to the disorder. In one, the individual already had a bleak view of the world before the trauma. They might have felt, “The world is out to get me”. When the trauma occurs, the schema is ‘confirmed’. Suddenly, absolutely everything they see or hear is perceived as negative.

For the other route, an individual had overly optimistic schemas before the trauma. They might have thought, “The world is benevolent”. After trauma, the old schema cannot adapt to the new information. They cannot possibly believe that the world is benevolent any more, but are unable to form a new, realistic schema. They then feel bombarded by stimuli, as they now have difficulty categorizing the information entering their brain.

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