Thank you for your question. There are many signs of depression. Of course, feeling sad, anxious, or "empty" can be a sign of depression, yet there's actually a lot more to it. Feelings of guilt, worthlessness, helplessness, hopelessness or pessimism are also often a part of it. When people feel this way, they may also experience a loss of interest in things that that they used to enjoy. Irritability and restlessness can also be signs. Often people can feel tired, and have less energy than they used to. Insomnia, early–morning wakefulness, or excessive sleeping are common. And they can also have difficulty concentrating, remembering details and making decisions, or have problems with overeating, or appetite loss. Sometimes there are thoughts of suicide, or even suicide attempts. There can also be persistent aches or pains, headaches, cramps or digestive problems that do not ease even with treatment. The good news is that there are effective treatments for depression! You can help a loved one by letting them know that these treatments exist, and may include cognitive behavioral treatment, medications, and exercise. They can go to this website to learn how to find help: http://www.nimh.nih.gov/health/topics/getting-help-locate-services/index.shtmlThe best thing for a loved one to do is to let the person know about how to get help, and to let them know that you care. Best of luck to you and to your loved one.