MELATONIN induces and improves sleep

The need for darkness in order to produce MELATONIN is the reason why sleeping in total darkness is so important

An increase in serum MELATONIN levels, occurring ~ 9pm daily, signals the initiation of normal sleep onset

-   At night, the MELATONIN ▲  increase indirectly reduces production of DHEA▼ (the consciousness hormone).   Achieved by MELATONIN's ▲  inhibitory action on PROLACTIN ▼ (PRL) production (PRL▲ is shown to stimulate DHEA ▲  production).

-   Slow wave sleep (SWS) occurs when MELATONIN is in greatest concentration.   Thus during stage 4 (the deepest SWS), MELATONIN ▲  ▲  ▲  should be in greatest concentration and DHEA ▼ ▼ ▼ least. MELATONIN and DHEA cycle through the night with overall MELATONIN declining and DHEA increasing.

Different Stages of Sleep

MELATONIN improves the efficiency of sleep.    Allows a person to spend a shorter time in bed to get a given amount of sleep; it does not improve total sleep time;

Having a light on at night squelches the production of MELATONIN.    Dampening your mood, and possibly resulting in increased appetite and unwanted weight gain. When sleep deprived, your body decreases production of LEPTIN, the hormone that tells your brain there is no need for more food, whilst simultaneously increasing levels of GHRELIN, a hormone that triggers hunger.