Nexus, the adult benefits are subtle, and include mental and emotional ones. It's to do with overall immunity, and so on. But again, individual factors prevail. No-one can ever say definitively that having been BFed as a baby will do X, Y, and Z for you as an adult, because everyone is unique. They do know the basic benefits with basic other factors taken into account (ie average lifestyle), and that's it, I guess. Again, I would say "why not give it a go if you can do it and want to do it", as opposed to insisting that everyone BFed their kids and felt bad if they couldn't or didn't want to.
Writer is correct that it is proven, however, that breastfeeding a child has benefits for the mother. That remains even with other factors. They first decided to investigate these when they started to notice that nuns are statistically miles more likely to have female cancers than any other group of women, and loads of research showed that the defining factors were them not having children to a minor extent, but not having nursed a child to quite a significant extent. That's not saying that any mother who hasn't BF will get cancer, of course not, just that Bfing gives some benefits.
And Writer, you will get there, trust me. I was saying the same as you at 11, 12 weeks, but it does improve. Sometimes, they just need to get older and deepen their latch.