(c) If the injury combines with a preexisting work related compensable injury, disability, or impairment, the subsequent injury is compensable if the subsequent employment or subsequent employment related activities contributed independently to the disability, impairment, or need for treatment.
The term does not include a mental injury arising from emotional, mental, or nonphysical stress or stimuli. A mental injury is compensable only if a compensable physical injury is and remains a major contributing cause of the mental injury, as shown by clear and convincing evidence. A mental injury is any psychological, psychiatric, or emotional condition for which compensation is sought;