_If depression is caused by a chemical imbalance in the brain, then how can it possibly be tied to injury?”
Depression, that occurs after injury, is not at all related to the injury. The depression may have existed for a considerable period and simply not been detected.
Individuals with recurrent major depression have a series of major depressive episodes and will continue to have these episodes. Some personalities are more prone to these.
There is a form of mild-to-moderately depressed mood, however, that does occur in some people after injury. This is _situational_ depression and is tied to realistic worry, fear, pain, and uncertainty. This is called an adjustment disorder.
There is also a form of depressed mood that is diagnosed when a person has had moderate depressive symptoms spanning at least two years. This is called dysthymic disorder as we have discussed in the past.
The physical symptoms, however, of major depressive disorder do arise from chemical changes in the brain. These may be of longstanding nature and simply not recognized until the person is receiving care for an injury.
Adjustment to an injury, however, can amplify these physical symptoms of depression.
This is why it is imperative to have an early psychological examination and to determine what role, if any, an injury has in the development or perpetuating of depressed mood of the injured worker. “