Continuous Disruption of the Sleep Cycle

Melatonin is produced by the pineal gland. Darkness stimulates melatonin production to help the body know when it is time to fall asleep. However, long-term use of melatonin may actually disrupt your body's ability to regulate that cycle. The body will acclimate to lower dosage levels, so users will have to increase the dosage to achieve the same benefits as before. Higher dosages increase the risks of adverse side effects.

Long-Term Risks of Biological Melatonin Supplements

Melatonin supplements can contain synthetic melatonin, which is created by chemicals or comes from animal sources. Animal sources are considered riskier, since they may contain biological contaminants or viruses. Permanent neurological damage or life-threatening illnesses could potentially be contracted from the use of these products.

Side Effects

Immediate side effects of melatonin can include: irregular sleep patterns, vivid or unusual dreams, irregular heart rhythm, nausea, dizziness, itching and headaches. These side effects subside when you quit taking melatonin; they may even subside if you reduce the dosage. However, if you suffer from any of these effects when you begin taking melatonin, they will be present for the duration of your supplementation with it.

Potential Long-Term Side Effects

Since melatonin is a hormone, its safety for use in prepubescent and teen-aged children who are undergoing hormonal development has been questioned. There have been no solid facts stating that it either does or does not disrupt the normal hormonal development of this age group.

Long-Term Side Effects

In adults, there is the potential for increased depression, a decrease in sex drive and dysfunction of the reproductive organs. These side effects will last for the duration of supplementation, and possibly for a short while afterward as the body readjusts its melatonin levels.

Warnings

Pregnant women or those who are trying to become pregnant are advised not to take melatonin supplements. Also, people with liver disease, diabetes and high blood pressure should not take melatonin. Melatonin should only be taken when you can go to bed soon after; do not drive or operate heavy machinery after taking melatonin.