Richard Paul Evans said this quote

The study showed that chronic loneliness impacts out bodies as negatively as smoking two packs of cigarettes a day. Not the same way, of course, just the life risk part. And there's more bad news. The article went on to say that lonely people had worse reactions to flu shots that non-lonelies (I think I just made up that word; my computer put a red squiggly line under it) and that loneliness depresses the immune system. On other words, if you're lonely, not even your body wants to be around you, so it tries to off itself.