The vote, 8,792 to 6,157 in a mail-in balloting concluded Monday, may help to settle a long debate within the profession over the ethics of such work. Psychologists have helped military and C.I.A. interrogators evaluate detainees, plan questioning strategy and judge its psychological costs.
The association's ethics code, while condemning a list of coercive techniques adopted in the Bush administration's antiterrorism campaign, has allowed some consultation "for national security-related purposes."
The referendum, first posted on the Internet as a petition in May, prohibits psychologists from working in settings where "persons are held outside of, or in violation of, either International Law (e.g., the U.N. Convention Against Torture and the Geneva Conventions) or the U.S. Constitution, where appropriate," unless they represent a detainee or an independent third party. The association's bylaws require that it institute the policy at the next annual meeting, in August 2009.
Many military and civilian psychologists have resisted a prohibition, arguing that consultants provide some accountability, making sure that questioning does not become abusive, for example.
But they have now lost out.
Steven Reisner, a New York psychoanalyst running for the association presidency on the issue, called the vote "fabulous news."
"The membership has sent a strong message to the leadership of the association that it wants to see this ethical prohibition as policy," Dr. Reisner said, "and now it has to be policy."
He added that the association should add the ban to its ethics code immediately and work out details of its enactment in the coming months. "This is a major step, but it's a first step," he said.
Like other professional groups, the association has little direct authority to restrict members' ability to practice. But state licensing boards that can suspend or revoke a psychologist's license often take violations of the association's code into consideration.