What Does The Ending Of Shutter Island Really Mean?

The Damaged Mind Is Incurable

It's probably the most cynical interpretation of the film there is, but - depending on which side you fall regarding whether or not Andrew's relapse at the end is intentional - one of the most sensible options is to assume Andrew was always going to revert back to square one by the end of Shutter Island. If the viewer is to assume that what Dr. Cawley and Dr. Sheehan are saying in the lighthouse about Teddy/Andrew is all true, then it seems as though Andrew has been going round in circles for two years already. As Dr. Cawley says, Andrew keeps 'resetting', like "a tape playing over and over on an endless loop". Teddy slipping back into old habits unawares is, of course, tragic, but Shutter Island may still be hinting at more. As Shutter Island and the Ashcliffe facility act as a microcosm of America (and perhaps the world), it's possible that Teddy/Andrew, on the face of it an everyman, symbolises everyone with mental illness. The suggestion, then, is not just that Teddy's madness is inescapable, but that madness on a wider scale is cyclical, and inevitable for those with an already damaged mind. After all, given that an elaborate stunt like the one Dr. Cawley pulled on Shutter Island doesn't work for Andrew Laeddis, what hope is there for everyone else of ever truly being cured?