Are you depressed or just sad?: The Major Depressive Disorder Quiz

Sadness is an emotion felt by everyone at some point but major depressive disorder -- also known as clinical depression -- is experienced by a smaller, though significant, portion of the population.

One of the myths associated with major depressive disorder is that those who experience it will never feel normal again. That's not true. With help, they can be 100 percent again.

Sadness and major depressive disorder share some common traits but also have some clear distinctions.

Some researchers estimate that 5 to 8 percent of the population battles major depressive disorder, while others say it may be as high as 20 percent.

A doctor can make an evaluation based on a variety of factors, but there is no laboratory test for major depressive disorder.

You may gain or lose weight, become sleepless or sleep excessively and become sullen or angry. It's also possible to experience combinations of all the above.

One of the key distinctions between sadness and major depressive disorder is the length of time a person feels depressed. Major depressive disorder lasts for more than two weeks.

Bipolar depression is not the same thing as major depressive disorder. MDD may also be referred to as unipolar or clinical depression.

Mania is not a component of major depressive disorder but is a characteristic of bipolar depression.

Research indicates that females are more likely to experience major depressive disorder.

Regardless of what societal stigmas suggest, people who have strong character and will power are just as likely to have major depressive disorder as anyone else.

Corns or swollen tonsils may be aggravating, but it's a malfunctioning thyroid gland that can cause major depressive disorder.

Abuse of any kind can eventually lead to major depressive disorder.

Methyl tertiary butyl ether should never be found on or near your brain.

Much research has been done, but there is still much to learn.

A layoff can trigger major depressive disorder. A death or divorce can also lead to the condition.

If a doctor wants to pump your stomach because you're dealing with major depressive disorder, you'll want to get a different doctor.

During surgery a battery is implanted to stimulate the Vagus nerve.

People with major depressive disorder may become easily agitated, as well as particularly sad.

Major depressive disorder is a serious condition, and anyone who says you should shake it off doesn't understand MDD.