Is having more than one cat in the city cruel?

I think that one of the points the research is making is that left to their own devices with free options cats choose to spend far more time outside with it observed that "farm cats" range further and staying outside longer, while City cats have more closer contact with other cats in a smaller radius.

The question I would ask is whether there is sufficient evidence to conclude cause and effect. They have concluded meeting more cats in a smaller radius restricts their desire to roam which is causing stress. How do they know that traffic is not the cause of the stress and that the reason farm cats go so far is because they are worried by not meeting enough other cats?

As I said above I think it has to be looked at on an individual animal basis - some cats would be stressed on their own some are undoubtedly stressed by too close contact with others but it is not sheer numbers that needs to be looked at but more the individual relationships.