I think it's well worth pointing out here that the Stanford experiment is highly controversial among psychologists, and the high reputation it has among the general public is by no means reflected in its reception by professionals.
There are numerous critiques of the experiment from the point of view of its design and, perhaps more seriously, several recent "exposés", and a film, based on interviews with participants, which contain significant charges regarding the degree to which the results were deliberately engineered by the "prisoners" and "guards", out of boredom or mischief.
In addition, the psychologist responsible for the experiment, Zimbardo, has been attacked for giving out incorrect information about the trial design and the conditions under which the student participants took part.
Fnally, an attempt by a team of British psychologists to replicate the experiment under the same conditions that Zimbardo asserts he applied failed miserably.
As a result of all this, the Stanford experiment is actually not very widely taught in psychology classes and does not appear in quite a number of standard textbooks.
All of these charges would tend to suggest not only that the famous experiment was, at best, severely comprised, but also that it was much less likely than you might expect to inflict long term damage on the participants. For balance, you might like to know that Stanford maintains a resource that links to both major critiques of the study, and Zimbardo's defences of it.
Although Zimbardo did not conduct an immediate debriefing, which could have uncovered harm caused by the experiment, none of the prisoners displayed long-term mental health issues. In the years following the experiment, the participants engaged in post-experimental questionnaires and interviews that (according to Zimbardo) confirms this.
To my knowledge, none of the participants sued or took any lethal action. The intense 6-day ordeal did cause signs of depression in one participant and severe emotional distress in others, but it seems that most of those involved have lived relatively obscure lives since then.
Source: McLeod 2008
Any interveiw sorces would be greatly appreciated if anybody has any