By December that year, the Cacioppos were focused on treating anxiety and depressive or aggressive behaviors with a version of a naturally-occurring neurosteroid (a steroid formed in the brain) called allopregnanolone. Studies, including some by the Cacioppos, had shown allopregnanolone to reduce anxiety and to promote the regeneration of brain cells, and was being considered as a possible therapy for PTSD, traumatic brain injuries and Alzheimer’s.

It went on the market last year as Zulresso, as a prescribed treatment for postpartum depression at about $34,000 a prescription (because of the secondary effects associated with taking it, the medication is only available through a restricted program.) The Cacioppos found that perceived social isolation, too, was probably associated with an impaired ability to synthesize allopregnanolone – which is how the current clinical trial started.

Meanwhile in Germany, Rene Hurlemann, a professor of psychiatry at the University of Oldenburg, began testing oxytocin about a decade ago. It is known as the “love” or “cuddle” hormone because of its release while giving birth, breastfeeding and physical affection. Oxytocin could have salutary effects, Hurlemann hypothesized, on a number of conditions. He studied its presence in flirting couples, and then turned to its potential in treating social anxiety disorder and PTSD. Based on animal research, Hurlemann said, we know oxytocin is crucial to social bonds – could the hormone also be used to treat loneliness?