Depression is an extremely complex disease. It occurs for a variety of reasons. Some people experience depression during a serious medical illness. Others may have depression with life changes such as a move or the death of a loved one. Still others have a family history of depression. Those who do may experience depression and feel overwhelmed with sadness and loneliness for no known reason.
There are a number of factors that may increase the chance of depression, including the following:
Abuse. Past physical, sexual, or emotional abuse can cause depression later in life.
Certain medications. For example, some drugs used to treat high blood pressure, such as beta-blockers or reserpine, can increase your risk of depression.
Conflict. Depression may result from personal conflicts or disputes with family members or friends.
Death or a loss. Sadness or grief from the death or loss of a loved one, though natural, can also increase the risk of depression.
Genetics. A family history of depression may increase the risk. It’s thought that depression is passed genetically from one generation to the next. The exact way this happens, though, is not known.
Major events. Even good events such as starting a new job, graduating, or getting married can lead to depression. So can moving, losing a job or income, getting divorced, or retiring.
Other personal problems. Problems such as social isolation due to other mental illnesses or being cast out of a family or social group can lead to depression.
Serious illnesses. Sometimes depression co-exists with a major illness or is a reaction to the illness.
Substance abuse. Nearly 30% of people with substance abuse problems also have major or clinical depression.
Researchers have noted differences in the brains of people who are depressed as compared to people who are not. For instance, the hippocampus, a small part of the brain that is vital to the storage of memories, appears to be smaller in people with a history of depression than in those who’ve never been depressed. A smaller hippocampus has fewer serotonin receptors. Serotonin is a calming brain chemical known as a neurotransmitter that allows communication between nerves in the brain and the body. It’s also thought that the neurotransmitter norepinephrine may be involved in depression.
Scientists do not know why the hippocampus is smaller in those with depression. Some researchers have found that the stress hormone cortisol is produced in excess in depressed people. These investigators believe that cortisol has a toxic or poisonous effect on the hippocampus. Some experts theorize that depressed people are simply born with a smaller hippocampus and are therefore inclined to suffer from depression. — [**]
Fact: Humans are the only mammal that can’t swallow and breathe at the same time.
Every other mammal, and many other non-mammalian animals, can breathe while they eat. In fact, human infants are also able to do so, which lets them breathe while they nurse. We lose this ability around the age of 9 months, when our voice box drops as part of our development. As children and adults, the human voice box lays unusually low in the neck compared to other animals. This allows sound to resonate much more, which is why we are able to produce the wide range of sounds that makes up our speech.
Fact: You have a second brain in your gut.
Well, sort of. You have around 100 million neurons, more than are in your spinal cord, that line your gut from your esophagus to your anus. This is known to scientists as the enteric nervous system. This second brain is incapable of conscious thought and is largely responsible for digestion, but it does more than that. If you’ve ever felt “butterflies” in your stomach or felt as if you’ve been punched in the gut when receiving bad news, that was caused by your enteric nervous system. This also plays a roll in your overall mood, why certain foods can alter your mood and why bad situations or feelings often cause you to lose your appetite.
Fact: Loneliness is physically painful.
Ok, you probably knew that. But do you know why? Researchers at the University of California asked volunteers to play a computer game that simulated a simple game of catch with two other players. What they didn’t know was that the other “players” were just the computer and it was designed to leave them out after a few minutes of play, resulting in feelings of loneliness and rejection. They found that the feeling of loneliness is actually processed in the same part of your brain as physical pain, called the anterior cingulate cortex. This explains the human desire to fit in, to seek out companionship and helps to understand the power of peer pressure. Scientists are also hoping to use this information to help explain and treat some forms of depression.