A lot of melatonin benefits have been researched. The following uses have been researched and show (strong) evidence that melatonin is beneficial for these conditions. Melatonin has been tested in humans or animals. Please note that some of these conditions can be serious, and you should always consult a qualified healthcare provider to discuss the best treatment.
Multiple human trials have suggested that melatonin administered orally reduces the number of days required to establish a normal sleep pattern when melatonin dosage is started on the day of departure, at the bedtime of the destination timezone, and is continued for several days. Melatonin taken this way also diminishes the time it takes to actually fall asleep, it has a positive effect on alertness, and it reduces fatigue experienced during the day. Some studies however showed no benefit.
In conclusion, the scientific evidence does suggest that more than 50% of the people who use melatonin for jet lag benefits from its usage. More research is needed to determine the best dose of using melatonin for Jet lag.
Delayed sleep phase syndrome (DSPS)
Delayed sleep phase syndrome (DSPS) is also known as delayed sleep-phase disorder (DSPD) or delayed sleep-phase type (DSPT). It is a condition that delays the cycle of sleep and being awake. This causes our brains to release melatonin much later than usual, causing trouble sleeping. Basically this is the same as a jet lag, but without the flying.
Insomnia in older adults
As stated before, several studies have shown beneficial effects of using melatonin for sleeping. This is especially amongst adults above the age of 50. Results were already shown with doses of 0.3mg.