I'm not a historian but I know a bit about medicine. The chances of a solid answer to this question existing are close to zero and I thought it might be worth explaining why. In short, it's not much more than a century since we started even thinking about how to do research properly and, as the current "replication crisis" demonstrates, we're not very good at it yet.

These sorts of questions are incredibly difficult to answer because patterns of mortality have changed so much, largely as a result of precisely the technological changes you're interested in. There wasn't much heart disease a century ago because not many people survived long enough to get it. Nowadays the people that would once have died of heart disease are living long enough to get cancer.

It's also very, very difficult to assign causes to observational data (there is no feasible or ethical way to test this question with an experiment). A lot of the ideas we have about the causes of disease are just guesswork and prejudice, in part because getting useful data is really quite hard and interpreting it properly is harder still. A good example is the Whitehall Study which turned the popular image of heart disease - as a killer of high power men in high power jobs - on its head.

Also, there are some great medical historians around but this isn't the kind of thing they work on. It's an epidemiological question. Might be worth putting this in AskScience.

As /u/D-juice explains, finding a concrete answer to this will be extremely difficult. We still struggle to define/measure the occurrence of stress related illnesses today, so extending the analysis across a range of historical periods is a methodological nightmare!

However, you might be interested to learn that that the association between stress related illnesses and modernity (particularly new technology) isn't a recent phenomenon. It goes back to at least the mid-nineteenth century, when conditions such as 'neurasthenia' (a fairly vague term used to describe problems with nerves/anxiety/depression) were often linked to urbanisation, the development of new working practices, and high-speed communications technologies. Victorian newspapers were filled with advertisements for quack miracle cures, which often used electricity to 'treat' the problem. The science here is all very questionable, but it tells us something about broader cultural understandings of stress.

I've come across this a few times in my own research, which focuses on Victorian perceptions of America. America was closely associated with modernity in the Victorian imagination, and so these kind of stress related illnesses were also associated with the United States - in fact, they were sometimes refered to as 'Americanitis'. There's a nice, accessible article on the Smithsonian Magazine website about it, which includes some of the adverts I mentioned.