Major

depression

Major depressive disorder (MDD) characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities

also known as Clinical depression

Symptoms

A person must have five or more symptoms in any of those categories, occurring nearly every day for about 2 weeks, for that person to be diagnosed with a depressive disorder

Physiology symptoms
The patient always feels tired, the whole body hurts, and has strong changes in appetite and sleep. Even the simplest daily tasks like bathing suddenly became too much for them. Some people can't even sleep and they often wake up an hour or two earlier than usual. Some others sleep more than usual. Patients don't feel interested in activities that they used to enjoy.
Cognitive symptoms
Patient change their thoughts about themselves and their surroundings. They think slowed down. They become difficult to focus. At the same time, they feel guilty and worthless. They focus all their attention on flawed aspects of themselves. Thoughts of suicide gradually become more pronounced. After a while, they thinks things will get better if they die.
Emotion symptoms
Feeling very sad, empty or hopeles are the most common and most visible symptoms of depression. And because the part of brain responsible for emotions is also the part responsible for the physical pain, when emotions are negative, body also feels pain
Behavior symptoms
The most noticeable behavior in these people is slow action. Patients walk and talk as if they were in slow motion. Some people also become helpless, unable to move and stop talking, or they may pause for a few minutes before answering a question.

A regular person may have a bad day, at the end of the day they buy an ice cream. Suddenly someone bumps into them and causes the ice cream to fall to the ground. They may feel angry but ultimately choose to buy another one. In contrast, a person struggling with depression may react quite differently. If their ice cream falls to the ground, they become overwhelmed with feelings of worthlessness and burst into tears. They go home and harm themself.

Everything... happening around me became completely numb.

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Dysthymia