Insurer seeks review of the Workers’ Compensation Board’s order that determined that claimant sustained a compensable worsening of a preexisting personality disorder.

Our review is de novo. Except for a 21-month period, claimant worked for the Josephine County Sheriffs Department from February, 1974, until March 15, 1985. He had a good work record until August, 1984, when his supervisor disciplined him for an incident involving a struggle with a suspect. In the succeeding months, his superiors subjected him to a series of disciplinary actions that culminated in his discharge on March 15, 1985. Insurer denied the stress claim that claimant filed.

The referee found that claimant had good performance evaluations every six months through June, 1984. The parties stipulated, and the referee found, that the disciplinary actions involving claimant were real events that occurred during the course and scope of his employment and were capable of causing stress. The referee also found that the employment conditions, when compared to “the off the job and non-course and scope factors,” were “the major contributing cause” of claimant’s symptoms. Based on the medical testimony, however, the referee concluded that claimant was suffering from a noncompensable preexisting personality disorder and that the claim was not compensable.

On review, the Board reversed the referee. It stated that

“the symptoms of a preexisting personality disorder and the disorder itself are one and the same; if the symptoms worsen, the underlying condition has worsened. Our decision was dictated by the Court of Appeals’ holding to that effect in Adsitt v. Clairmont Water District, 79 Or App 1, 6, 717 P2d 1231, rev den 301 Or 338, 301 Or 666 (1986). We reaffirm that rule in this case. Claimant, therefore, sustained a compensable worsening of his preexisting personality disorder and [insurer’s] denial must be set aside.”

We affirm, but on other grounds.

We have reviewed the extensive medical evidence. We find that claimant was suffering from an occupational *135stress disorder, and not from a preexisting personality disorder. We also find that stressful conditions objectively existed on the job and that the employment conditions, when compared to non-employment conditions, were the “major contributing cause” of claimant’s disease. See McGarrah v. SAIF, 296 Or 145, 166, 675 P2d 159 (1983). Claimant suffered from an occupational disease which is compensable. Former ORS 656.8021.

Affirmed.