Major Depressive Disorder, also known as Clinical Depression, is one of the main illnesses that psychiatrists deal with. And it's not simply a matter of being, just having depressed mood, or being bummed out when something bad happens. It's a specific constellation of symptoms. Now one of those symptoms that you have to have is, having depressed mood, but that's severely depressed mood for most of the day, every day. And the other possibility is something called Anhedonia, or the inability to experience pleasure, in activities that normally gave one pleasure. One common example is parents who suddenly don't enjoy spending time with their children, but it can be any activity that people used to enjoy, and no longer derive any pleasure from. Other symptoms are, an appetite disturbance. Most characteristically, this is a loss of appetite, but for some individuals, they eat excessively. Another one is a sleep disturbance. Most characteristically, this is early morning wakening. So patients will wake up early in the morning, and not be able to fall back to sleep, but still don't want to get out of bed. Other signs are: A difficulty concentrating, feelings of worthlessness or guilt, decreased energy. And then, the final one is psychomotor retardation or agitation. In other words, an increase or decrease of activity that's observable by other people. The reason that it's so important to identify symptoms of depression is because we have treatments that work very well. The best treatment is a combination of medications and psychotherapy. It's very important to get an evaluation, to make the diagnosis early, because a lot of the worst consequences of depressive symptoms can be prevented, with early diagnosis and treatment. And most significantly, that can be suicidal thinking, and suicidal acts. So it's very important for individuals suffering any of these signs or symptoms to get an evaluation with a psychiatrist, so that they can start treatment early, to prevent the worst consequences of these symptoms.