Depression is a depressed mood (for at least 2 weeks), feeling of sadness, loss of interest and pleasure in most activities, disturbance in sleep and appetite as well as deficit in cognition and energy. Thoughts of guilts, worthlessness, suicide is common. Depression is not an easy condition to tackle with.
A person having other bodily dysfunction, disorder or disease, he/she normally experiences clear cut symptoms and signs like if a person has abdominal discomfort or backache, he/she will have clear feeling and can depict it. Mental pain is less dramatic than physical pain but it is harder to bear. Depression is like a barometer, it tells us that something is wrong but it does not tell us what is wrong. Complicating the condition is the fact that it is experienced differently by each person. Depression is just a feel, a WORST FEEL.
It is important to mention here too that some people if they are feeling down, they depict as if they’re depressed. Stop normalizing the word ‘depression’ in daily life. It’s not just simple sadness. It is a serious clinical condition. It’s an illness to which patient not only has to deal with but also to fight with. One can get relieve from tensions and worries but depression is a medical condition requiring proper attention. Depression is not always black and white. It is colorful sometimes. People having smiles on their faces and literally dying inside.

Understand the Difference between Tension and Depression
So, at first we all need to understand the difference between Tension and Depression. Depression is feeling alone despite everyone is around you. All negative thoughts surround you. However, depression manifests differently in different individuals. Some people may become violent while others want to cry their heart out. Imbalance of emotions. Sometimes it is even tough to differentiate between right and wrong. Sometimes it feels you are moving in deep dark tunnel from where there is no way back, living a purposeless life. But there is always light after dark, hope after despair, rise after fall and these are enough to bring out the best version of yourself, enough to make you strongest. So, lets get out of it.
There can be a lot of causes of depression but if I discuss with reference to medical sciences, deficiency of some of the chemicals in body particularly serotonin is the cause (sometimes dopamine known as happy hormone). It can also be due to prolonged stress, trauma, weakness, injury to brain and it can also be inherited. Regardless of the cause, focus should be to get rid of it.