Depression is a mood disorder that affects more than 14 million Americans each year, according to the Depression and Bipolar Support Alliance. It is characterized by sadness, loss of interest in regular activities and despair.

Serotonin is a hormone made between the brain and digestive tract that also works as a neurotransmitter. Its primary role is to help you feel calm, promote sleep and cause blood vessels to narrow. People with low serotonin levels suffer from insomnia, depression or both.

Levothyroxine helps regulate your metabolism and energy, as it is a replacement for a hormone your thyroid normally produces that does this. Levothyroxine is used to treat low thyroid hormone levels in your body, called hypothyroidism.

Serotonin is a chemical produced by nerve cells in the brain. Low serotonin levels in the body are linked to instances of depression as well as insomnia.

If your doctor has prescribed Celexa (citalopram hydrobromide) for depression, you may wonder if the drug will affect your weight. Some antidepressant drugs can cause weight gain, a side effect that patients sometimes dislike so much that they stop taking their medication.

Depression affects more than 6 percent of the adult population in the United States. The National Alliance on Mental Illness warns that being single or widowed elevates the risk for this disorder.

Paranoia and depression do not commonly occur together, but when they do they can be signs of a serious underlying psychiatric condition.

Angina pectoris, or angina, is chest pain or discomfort that happens when a part of the heart does not get enough blood and oxygen. People who experience angina are at higher risk for a heart attack or cardiac arrest.

Depressant drugs are prescribed to relieve tension, anxiety and irritability. In addition, depressant drugs can treat insomnia. Orally taken, depressant drugs have a high potential for abuse, according to the U.S. Department of Health and Human Services.

Serotonin, also called 5-hydroxytryptamine (5-HT), is a neurotransmitter, a chemical required for the healthy functioning of your brain cells, nerves and gastrointestinal tract.

If you often wake in the middle of the night feeling very hungry, you might need to change your daytime eating patterns. In rare cases, you might have a medical condition known as night eating syndrome, but for most people, waking up hungry during the night means you’re not eating well during the day.

Caffeine is the most commonly used stimulant in the world. It has been used for centuries to help invigorate the senses and energize the body. Many people use coffee, tea, energy drinks or caffeinated soft drinks as a way to boost energy and alertness at the start of a new day.