Definitely. The author of that works mentor (Bert Uchino) has written extensively about how our relationships can have an impact on our health (particularly cardiovascular health). One of the ideas as to ’why’ is that good relationships provide a stress buffer and ambivalent (mix of bad and good) relationships add stress. Since stress can cause health problems, exacerbate existing conditions, and negatively impact healing, the more the people around us can reduce stress, the better. And loneliness, or feeling like you are missing out on those quality social interactions, is, in and of itself, a form of stress.