The first episode of depression is known as a single episode, subsequent episodes are termed recurrent.
In order for a person to be diagnosed with mild depression or a mild mood disorder, they would only have a couple of symptoms (if any) above what is required to make a diagnosis. In most cases the person can still function normally with a little extra effort.
The severity and number of symptoms is more than in someone experiencing mild depression. During what is known as a manic episode, a person diagnosed with moderate depression shows significantly impaired judgment and decreased activity.
Major Depressive Disorder
A person can be diagnosed with severe depression but some cases can be accompanied with psychotic features, in order for a diagnosis of severe depression, there would be a multitude of symptoms and the patient would have difficulty carrying out even the most simplest of tasks such as cleaning their teeth. Severe cases of depression, often require the patient to be under constant supervision in order to protect them from harming themselves or others. It is thought that 15 percent of patients diagnosed with major depressive disorder will develop psychoses marked by delusions and hallucinations. These psychotic features put the patient at great risk as they are often unable to make appropriate judgements of the consequences of their actions and are particularly prone to self-harming.
Requirements for full remission are met when a person has been free of symptoms of depression for a minimum of two months. A patient is said to be in partial remission when they no longer meet all of the criteria be diagnosed with major depressive disorder or that symptoms have subsided for less than two months.
Chronic depression is the term given to someone who has suffered from the symptoms of major depressive disorder for more than three episodes of for longer than 2 years.