The role of US psychologists in helping to interrogate detainees at Guantanamo Bay and at CIA "black sites" overseas may be at an end after members of the profession voted against the practice.
The American Psychological Association (APA), which represents thousands of psychologists, voted to ban such work.
In the past, the US military and the CIA have drafted in psychologists to evaluate suspects, plan interrogations and judge the "psychological cost" of different tactics.
Until now, the APA's ethics code had condemned specific coercive practices employed during the "War on Terror" but had allowed some consultation for "national security-related purposes".
However, there remains scepticism about whether the vote will halt psychologists' involvement in interrogations. As with other professional associations, the APA has little direct authority to restrict members' practices, although violations of its code are taken into account by state licensing boards.
Speaking to The New York Times, Alan E. Kazdin, president of the APA and a psychologist at Yale University, said: "The membership has spoken, the process worked and we're going to follow it. Will everyone be happy? Well, it's a typical human enterprise and there are nuanced positions on both sides, so we'll see."
Steven Reisner, a psychoanalyst running for the APA presidency on the issue, added: "The membership has sent a strong message to the leadership ... that it wants to see this ethical prohibition as policy, and now it has to be policy. This is a major step, but it is a first step."