Millions of people have a depression. In a report from WHO (World Health Organisation) from 2015 it says that more than 350 million people are affected worldwide.
On average about 1 in 20 people reported having an episode of depression.
"Depression is a common mental disorder, characterized by sadness, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, feelings of tiredness, and poor concentration.
Depression can be long-lasting or recurrent, substantially impairing an individual’s ability to function at work or school or cope with daily life. At its most severe, depression can lead to suicide. When mild, people can be treated without medicines but when depression is moderate or severe they may need medication and professional talking treatments."
There are so many different types of depressions, with so many different levels (mild, mediocre, severe), different versions (mothers who have postpartum depression, so called baby blues, seasonal affective disorder or bipolar disorder) that hit you in different waves and portions.
A lot of people and societies look at depression as a weakness in a person's character, as something the person should snap out of and simply deal with.
If I had cancer, people would be more understanding with my situation and sympathetic because cancer is considered a terrible disease. Why is it considered a terrible disease? - Because it is disease. And so is depression. It doesn't have one single cause - brain chemistry, hormones, and genetics all play an important role.
Then again there is so much discussion going on about whether depression is an actual disease or not. I'm not a scientist or doctor. I'm not trying to argue. I want to draw attention to symptoms that are real for so many people. Symptoms that can lead you to suicidal thoughts.
If your child or husband or girlfriend or mother had these symptoms, would it matter whether depression is a disease or not? All that would matter is that there was a health system that knows how to deal with it beyond pharmacological treatment, a social net that was informed, understanding, and supportive, a way out of darkness and sadness and away from suicidal thoughts.
Have a look at this article from Healthline to read a quick summary on depression.
Here is a great animation that envisions how it is to live with depression.