I mean, it's not amnesty international, but a UN Special Rapporteur on Torture claimed:

"Mr. Assange has been deliberately exposed, for a period of several years, to progressively severe forms of cruel, inhuman or degrading treatment or punishment, the cumulative effects of which can only be described as psychological torture."

https://www.ohchr.org/EN/NewsEvents/Pages/DisplayNews.aspx?N...