HTP is short for a substance called hydroxytryptophan. HTP is used by the body to make the neurotransmitter serotonin. Serotonin plays a key role in three different areas: mood, sleep, and appetite. HTP has been historically used as a supplement to help people that have issues for all three of these areas.
In the case of sleep, serotonin is converted to melatonin--the hormone that helps the body sleep. Nature's Sunshine has a product called Melatonin Extra that could be helpful. Those struggling with sleep can try several different approaches--a warm bath with aromatherapy candles, for example. Scents of chamomile and lavender have historically been helpful for many. Of course, nervine herbs such as passion flower, hops, and valerian have also been used. Nature's Sunshine has a product called Herbal Sleep that actually combines all of these.
Doctors often prescribe SSRI drugs for those with depression, where a low level of serotonin seems to be the issue. These drugs are meant to affect serotonin reception. (In fact, SSRI stands for Selective Seronin Reuptake Inhibitor.) It seems that 5-HTP can have similar effects as some SSRI drugs; however, one should never make this substitute without the consent and advice of their doctor. Mood Elevator and St. John's Wort are possible complementary products. St. John's Wort in particular has gotten a lot of attention over the years as an herbal approach for mild to moderate depression. For severe depression, its benefits are limited.
Finally, some people use 5-HTP as a weight loss supplement in cases where appetite suppression or control of food cravings is needed. Low serotonin levels have been linked to certain food cravings, thus the use of 5-HTP. In 2013, Nature's Sunshine reworked parts of their Weight Loss line and made a couple of nice products for help in this area as well. Stixated is an appetite control product that you should consider. Also, Sweet FX--as it helps suppress sugar absorption and thus may help mood at the same time (often mood swings and sugar swings are related).
IMPORTANT NOTE: These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. All statements are based on historical or anecdotal use of herbs and natural remedies. If a serious health condition exists, one should see a qualified medical doctor rather than rely on information given on this website.