Many patients find themselves getting very emotional when in pain.
Crying spells, depression, and moodiness are not uncommon. This system is old from an evolutionary stand point, so these signals end up in primitive parts of the brain responsible for controlling emotions. A good example is an effect seen by massage therapists and body workers for centuries. When working deep in a patient's muscles, many therapists note that the patient will sob uncontrollably. The reason is that these pain impulses have a direct link into the parts of the brain that control emotion.