Sadness and depression could go hand in hand, but the reality is that the terms are confused, and the differences must be known because it is a fundamental issue for health.
Being sad does not mean being depressed. Crying is normal and is a natural emotional state that can be felt at many moments in life, and even serves an adaptive function. It responds to particular circumstances like the loss of a loved one, a romantic breakup, a conflict or discussion or hormonal changes.
Depression is a chronic state of distress and sadness in which the person is unable to cope with normal situations and have impaired nervous and immune systems. Emotions limit it and depressive feelings last longer than normal.
Not all people with depressive illness have the same symptoms and may vary. According to the World Health Organization the symptoms are: loss of interest and ability to enjoy, energy reduction, anxiety symptoms, sleep and appetite alterations, feelings of guilt and low self-esteem, difficulties of concentration and even symptoms without medical explanation.