People with depression are not just sad. Their depressed mood is constant and lasts for a period of time and /or leads to a loss of interest or ability to enjoy and accomplish usual activities.
They lose interest in work and relationships. They can be irritable. They may experience sudden weight gain or weight loss.
They may sleep all the time or very little. They have difficulty getting up to face the day.
They may drink excessively or use drugs to help manage their overwhelming feelings.
They have thoughts such as “the world would be better off without me.” Some act on these thoughts and attempt suicide.
Others hide what they are really thinking and put on a brave face when among others.