'Addiction' ended Swank marriage

Chad Lowe and Hilary Swank met at a party in 1992

Oscar-winning actress Hilary Swank says her split from husband Chad Lowe was partly down to his "substance abuse".

"When I found out it was such a shock, because I never thought he'd keep something from me," the Million Dollar Baby star told Vanity Fair magazine.

Swank, 31, and actor Lowe, 38, announced their intention to divorce in May after eight years of marriage.

Lowe's spokesperson had no comment on the article, which did not specify which substance the actor was abusing.

But Swank said the actor was dealing with his addiction.

"He's living a sober life," she said. "I know how difficult it is, and I'm really proud of his sobriety."

It made me look at things a lot deeper - that's when you realise it's not going to work Hilary Swank

She added that Lowe's substance abuse was not the sole reason for the end of their marriage.

"But that just kind of blew it open," she said. "It made me look at things a lot deeper.

"That's when you realise it's not going to work."

The couple met at a party in 1992 when Swank was 18. They married five years later.

The actress famously forgot to thank Lowe when she won her Oscar for Boys Don't Cry in 2000, but remembered when she won again four years later.

She will next star in Brian De Palma's adaptation of James Ellroy's The Black Dahlia.

Lowe - the brother of actor Rob - has had roles in more than 30 television films and several movies since making his big-screen debut in 1984 with a small role in his brother's film Oxford Blues.

He won an Emmy in 1993 for his portrayal of an Aids sufferer in TV series Life Goes On.