The last controlled jet-lag trial of melatonin was reported in 2004
Every placebo-controlled test after a real flight dates from 1986 to 2004, and one 57-person trial finished in 2007 and has posted no results.
What the study found
Controlled melatonin trials on real flights all date from 1986 to 2004
Every placebo-controlled melatonin trial after a real flight was reported from 1986 to 2004, most by 2001, and reviews in 2014 and 2021 found none newer. A registered trial of 57 people finished in 2007 and has posted no results. The trial evidence behind today's advice is that early set.
The caveat · Counts melatonin, not newer drugs
Laboratory studies of melatonin and the body clock continued after 2004, without flights. Newer drugs that act on melatonin's receptors have had jet-lag trials of their own, which this count leaves out. The registry figure comes from the main US trial registry alone.