i) Introduction

Factors affecting the risk of psychiatric illness after a TBI include:

• Pre-injury characteristics
• The injury
• The setting: the social and service context.

 

ii) Pre-injury characteristics

Any person who has a traumatic brain injury comes to that traumatic brain injury with a number of pre-injury characteristics. These characteristics may influence whether or not the person develops a psychiatric illness.

Genetic inheritance

One of the most important pre-injury characteristics is the genetic vulnerability the person has. Family history provides clues to this genetic vulnerability.

A person who has a family history of psychiatric illness seems to be more vulnerable for developing a psychiatric illness after their traumatic brain injury.

If the person has a pre-existing history of psychiatric illness they too are more vulnerable to developing psychiatric illness after their brain injury.  That psychiatric illness may be altered by having the brain injury itself.

Drug and alcohol use

A history of drug or alcohol use, problems in drug and alcohol use prior to the time of the injury is a risk factor for psychiatric illness after traumatic brain injury. There seems to be a higher risk of mental illness associated with a pre-existing history of drug and alcohol use.

Drugs and alcohol are often implicated in the actual cause of the brain injury, for example, driving under the influence or being intoxicated while crossing the road. The drug and alcohol use can in its own right increase the person's vulnerability to brain injury, due to increasing impulsivity and risk taking behaviours.

Cultural background

The cultural group the person is from is also an important influencing factor. Language in certain cultural groups lacks any kind of equivalent to our words such as depression, sadness or low mood. In addition, in certain cultural groups particular aspects of behaviour are accepted or considered within the realms of normality. Therefore whether we can determine whether they had a psychiatric illness prior to the injury may be influenced by cultural factors.

Employment / unemployment

Whether the person was employed prior to the injury also influences their outcome from the brain injury. Unemployment seems to incur a greater risk of the development of mental illness. The person who is unemployed prior to the traumatic brain injury has a greater risk of psychiatric illness after the traumatic brain injury.

Social support and family environments

Limited or absent social support increases the risk of psychiatric illness post traumatic brain injury.

All these factors come with the person with TBI. They are factors we can not influence or change.

 

iii) The injury

The second set of factors affecting the risk of psychiatric illness after a traumatic brain injury are the severity of injury and the location of the injury.

In Australian society the most common type of traumatic brain injury is closed brain injury.

Earlier published studies on psychiatric effects of brain injury were done in patient populations where there were open head injury, in particular war injuries. The famous studies by Lishman that were published in the 1960’s were based on populations who sustained war injuries most of the time which were open head injuries. This is also true of studies published in the past decade which have often used military samples.

The comparison of open head injury population to closed head injury population is not very good.  They are not necessarily comparable groups.

More commonly in a modern society when a person has a closed head injury it is caused by acceleration and deceleration of the brain within the cranial vault. This causes damage to the white matter and typically what we call diffuse axonal injury or sheering injury.  The range or areas of the brain that are damaged are widespread, particularly in high velocity injury such as motor vehicle accidents.  Bleeding can occur acutely, leading to extradural, subdural and surarachnoid harmorrhage.  Bleeding may occur inside the brain causing intracerebral contusions. 

In addition to the acute injury that occurs there is also secondary damage due to the swelling of the brain. There may be haemorrhage and pressure effects of local contusions. Metabolic effects of oxygen deprivation if the person's airway is obstructed at the time of the injury.

There will be the acute effects, directly from the injury, and possibly secondary effects of the brain injury and subsequent changes on a microscopic level, mechanically and biochemically. These factors may be modifiable by medical intervention.

 

 

iv) Social and service context

Setting

The third important interacting factor that influences whether a person has psychiatric illness are the post-injury factors that often can be influenced or altered. Those post-injury factors relate to the setting in which the person is being managed.

In some cases traumatic brain injury can be missed, particularly if there are substantial injuries to the long bones or there is injury to the abdomen and the chest. In these situations because of the critical life threatening nature of these injuries, a traumatic brain injury can be missed and therefore not diagnosed until sometimes weeks or months after the injury.

This influences the type of psychiatric illness that emerges and often the type of behavioural disturbances that we see.

Family and family environment

Other important factors include the family and the family environment, the amount of support that the person has. This can influence the emergence of psychiatric disorders, in particular the mood disorders.

Compensation and litigation

Finally, whether or not there is compensation or litigation can influence the emergence of psychiatric illness . The experience of being involved in litigation is very stressful for people - whether their injury is mild to extremely severe. Compensation claims are usually only settled some years after the accident and there is often an extended process of legal negotiation which is very stressful.  To a certain extent being involved in the litigation process is a bit like going on a very long, emotional “rollercoaster ride.”  It is the litigation and the stress associated with it that can influence how psychiatric illness is expressed and also the type of psychiatric illness that may occur.

Some people who are involved in litigation often develop paranoid disorders because they feel that they are being spied on or supervised. There is often an element of reality to this which can impact on the emergence of the paranoid disorders.

For some people there is an aspect of secondary gain whereby the legal process reinforces helplessness or lack of effort in rehabilitation.  In addition, there are cases where the person gets special treatment from their family or their workplace which reinforces the sick role.

Interrelationship between psychiatric illness and traumatic brain injury

When we look at the interrelationship between psychiatric illness and traumatic brain injury there are some very important facts to remember. When a person has a brain injury the brain injury in its own right is going to alter the presentation and the progress of the psychiatric illness even when this was a pre-existing disorder.

Someone who has got a very well established bipolar disorder and has a brain injury may have a substantially changed presentation. Their response to management may also be significantly changed.