Section 451.001 of the Texas Labor Code prohibits an employer from discharging an employee for filing a workers' compensation claim in good faith. See TEX. LAB. CODE ANN. 451.001 (Vernon 1996). To prevail on a section 451.001 claim, an employee need not show he was fired solely because of filing the workers' compensation claim; rather, she must show that "but for" the filing of the claim, the discharge would not have occurred when it did. See Continental Coffee Prods. Co. v. Cazarez, 937 S.W.2d 444, 450-51 & n.3 (Tex. 1996). Circumstantial evidence sufficient to establish a causal link generally includes: (1) knowledge of the compensation claim by the person terminating her; (2) expression of a negative attitude toward the employee's injured condition; (3) failure to adhere to established company policies; (4) discriminatory treatment in comparison to similarly situated employees; and (5) evidence that the reason for the discharge was false. See Continental Coffee Prods. Co., 937 S.W.2d at 451.