It was rated "A" in the UK, which was more or less the equivalent of PG at the time, after psychologists advised the British Board of Film Classification that the film would probably disturb adults more than children (the film was also tested on an audience of children, who apparently all loved it). I'm evidence of that, I think, but actually you are evidence of the opposite.

It's since been rerated 12A in the UK (equivalent of PG-13 in the US).