How does depression differ from grief or mourning?

Grief and mourning are natural responses to loss, whereas depression is a mental health disorder that can occur with or without a specific triggering event. Although all may involve sadness, withdrawal, and changes in sleep or appetite, grief typically comes in waves and is often focused on the person or thing that was lost. Depression tends to be more persistent and pervasive, affecting a person’s mood, sense of self-worth, and ability to function. Feelings of hopelessness, worthlessness, and loss of interest in nearly all activities are generally more characteristic of depression than of grief.