New Jersey Gov. Chris Christie signed a bill banning the practice of administering therapy to gay minors to convert them into being straight, a move by the Republican governor that surprised some of the bill's backers.

Mr. Christie said that while he doesn't back government encroaching on parents' ability to make decisions for their children, research has shown that forcing young people to change their sexual orientation can pose health risks.

In particular, Mr. Christie wrote in a bill signing Monday, the American Psychological Association has found that gay conversion can trigger depression, suicidal thoughts and substance abuse.

"I believe that exposing children to these health risks without clear evidence of benefits that outweigh these serious risks is not appropriate," Mr. Christie wrote in the one-page signing memo. "Based upon this analysis, I sign this bill into law."

Monday was the deadline for Mr. Christie to act on the bill banning "sexual orientation change efforts," known as conversion therapy. The bill prohibits professional counselors from administering the therapy to those under the age of 18.

New Jersey is expected to become the first state with a ban in force, according to Garden State Equality, the state's main gay group. California passed similar legislation, but it's being challenged legally.