Depression is a physical condition. Often it is triggered by environmental events (e.g. trauma, loss, etc). There is likely a genetic component since mood disorders can occur among first degree relatives.
Depression is expressed in the brain by a depletion of specific neurotransmitters and, therefore, compromised communication between brain cells.
It is true that there are articles in the recent wound literature that indicate that depressed individuals tend to heal more slowly.
Perhaps more importantly, the psychological components of depression include helplessness and hopelessness.
Depressed patients are less likely to extend full effort in physical therapy. They are less likely to attempt weight control. They are less likely to take their medications as prescribed.
And they are quite often unaware of, or unwilling to admit, their depression.
Thus, when healing is impeded by depression, it will be you who detects its existence and makes the appropriate decisions for intervention.
Always remember that depression impacts perceptions of pain, ability to sleep, regulation of appetite, sexual drive, memory, concentration, decision-making and enthusiasm. Determining its existence among patients with physical complaints can be crucial to implementing a course of intervention.