As used in the Workers' Compensation Act:
A. "impairment" means an anatomical or functional abnormality existing after the date of maximum medical improvement as determined by a medically or scientifically demonstrable finding and based upon the most recent edition of the American medical association's guide to the evaluation of permanent impairment or comparable publications of the American medical association. Impairment includes physical impairment, primary mental impairment and secondary mental impairment;
B. "primary mental impairment" means a mental illness arising from an accidental injury arising out of and in the course of employment when the accidental injury involves no physical injury and consists of a psychologically traumatic event that is generally outside of a worker's usual experience and would evoke significant symptoms of distress in a worker in similar circumstances, but is not an event in connection with disciplinary, corrective or job evaluation action or cessation of the worker's employment; and
C. "secondary mental impairment" means a mental illness resulting from a physical impairment caused by an accidental injury arising out of and in the course of employment.