Depression is a disorder that afflicts over 10% of the world's population, but we as a society know little about it. Stereotypes tell us that depressed people are weak, unless they happen to be a tortured artist. It can be difficult to understand depression, because it's invisible.

It's a disorder defined by thoughts, behaviors, and feelings, rather than obvious symptoms like vomiting, rashes, or fever. Those who have experienced depression are all too familiar with comments from misguided friends such as “ansp out of it”, or “just get up and do something”.

Even those with depression might have a hard time understanding what they are experiencing, and they often blame themselves for not being able to snap out of it. To understand what depression really is, we need to talk about symptoms.

First of all, depression has symptoms related to how someone feels. These symptoms include nearly constant feelings of sadness, anger, guilt, or hopelessness. Next, there are symptoms related to behavior. They include social withdrawal, a lack of energy, low motivation, poor concentration, sleep problems, or significant changes in appetite. Finally, symptoms related to thoughts include poor self-esteem, thoughts of suicide, and loss of interest in regular activities.

Symptoms of depression must last at least one week, and they are often cyclical. This means the symptoms can come or go over a period of months or years. A person who experiences depression once is likely to have future episodes. It can be difficult to think of these thoughts, feelings, and behaviors as symptoms. To many of us, they can seem like decisions. It can seem like someone who is depressed has decided to be lazy and sleep all day, or they have decided to stop spending time with friends because they have a bad attitude.

But remember: What's in our head isn't imaginary. Our thoughts, feelings, and behaviors are influenced by a complex series of chemicals in our brains. The exact causes of depressions are poorly understood, but we have an idea of factors that influence the illness.

We know that changes to hormones in the brain called neurotransmitters can have a major effect on depression. Many medications used in the treatment of depression work by increasing the levels of these neurotransmitters. We also know that genetics play an important role in depression.

People who have a family history of depression are more likely to experience the disorder. Just because your parents have depression doesn't mean you necessarily will, but the chances are greater.

Finally, we know that environmental factors play a role in depression. Living in poverty, experiencing a traumatic event, or other stressful situations may trigger the disorder. That being said, depression does not always have a clear trigger, which often leads to a person not understanding why they feel so down.

Treatment for depression usually includes psychotherapy and medication. Either can work on its own, but a combination of medication and therapy has been found to be the most effective. In summary, depression is a disorder that's widespread, but poorly understood. The symptoms can negatively effect a person's thoughts, feelings, and behaviors to a debilitating degree.

However, treatments that include medication, psychotherapy, or a combination of the two can help to eliminate the symptoms of depression.