(A) "Injury" and "personal injury" mean only injury by accident arising out of and in the course of employment and shall not include a disease in any form, except when it results naturally and unavoidably from the accident and except such diseases as are compensable under the provisions of Chapter 11 of this title. In construing this section, an accident arising out of and in the course of employment includes employment of an employee of a municipality outside the corporate limits of the municipality when the employment was ordered by a duly authorized employee of the municipality.

(B) Stress, mental injuries, and mental illness arising out of and in the course of employment unaccompanied by physical injury and resulting in mental illness or injury are not considered a personal injury unless the employee establishes, by a preponderance of the evidence:

(1) that the employee’s employment conditions causing the stress, mental injury, or mental illness were extraordinary and unusual in comparison to the normal conditions of the particular employment; and

(2) the medical causation between the stress, mental injury, or mental illness, and the stressful employment conditions by medical evidence.

(C) Stress, mental injuries, heart attacks, strokes, embolisms, or aneurisms arising out of and in the course of employment unaccompanied by physical injury are not considered compensable if they result from any event or series of events which are incidental to normal employer/employee relations including, but not limited to, personnel actions by the employer such as disciplinary actions, work evaluations, transfers, promotions, demotions, salary reviews, or terminations, except when these actions are taken in an extraordinary and unusual manner.

(D) Stress, mental injuries, and mental illness alleged to have been aggravated by a work-related physical injury may not be found compensable unless the aggravation is:

(1) admitted by the employer/carrier;

(2) noted in a medical record of an authorized physician that, in the physician’s opinion, the condition is at least in part causally related or connected to the injury or accident, whether or not the physician refers the employee for treatment of the condition;

(3) found to be causally related or connected to the accident or injury after evaluation by an authorized psychologist or psychiatrist; or

(4) noted in a medical record or report of the employee’s physician as causally related or connected to the injury or accident.

(E) In medically complex cases, an employee shall establish by medical evidence that the injury arose in the course of employment. For purposes of this subsection, "medically complex cases" means sophisticated cases requiring highly scientific procedures or techniques for diagnosis or treatment excluding MRIs, CAT scans, x-rays, or other similar diagnostic techniques.

(F) The word "accident" as used in this title must not be construed to mean a series of events in employment, of a similar or like nature, occurring regularly, continuously, or at frequent intervals in the course of such employment, over extended periods of time. Any injury or disease attributable to such causes must be compensable only if culminating in a compensable repetitive trauma injury pursuant to § 42-1-172 or an occupational disease pursuant to the provisions of Chapter 11 of this title.

(G) As used in this section, "medical evidence" means expert opinion or testimony stated to a reasonable degree of medical certainty, documents, records, or other material that is offered by a licensed health care provider.