It affects sleep itself, decreasing
sleep latency, increasing
sleep efficiency, and increasing the total
sleep time. Melatonin acts on the melatonin receptors.
Other neurotransmitters are neuropeptides like orexin-A and orexin-B which are basically involved in wakefulness. Excess of these peptides can also lead to insomnia.
The investigations which will help to diagnose the type and cause for insomnia are Polysomnography, Multiple sleep latency test and Actigraphy .