This is a great article by Maria Popova (who mentions she is a student of Tara Brach, which changed her life). Wide ranging in content she discusses placebo: you don’t have to be “tricked” (blinded trials) for placebos to work to make you well, loneliness is measurably different from solitude in it’s effect on your body and mind, faith and a sense of life purpose also have a positive effect of health outcomes and meditation is a kind of positive solitude that can change your brain structure for the good in just 11 hours of practice…

Though solitude might be essential for great writing, being alone a special form of art, and single living the defining modality of our time, loneliness is a different thing altogether — a thing Cacioppo found to be toxic:

Source: Rethinking the Placebo Effect: How Our Minds Actually Affect Our Bodies | Brain Pickings