The American Psychiatric Association (APA) defined depression and bipolar disorder in its 2005 brochures "Let's Talk Facts About Depression" and "Let's Talk Facts About Bipoloar Disorder (Manic Depression)":
"Depression is a serious mental illness that negatively affects how you feel, the way you think and how you act.
Depression has a variety of symptoms, but the most common are a deep feeling of sadness or a marked loss of interest or pleasure in activities. Other symptoms include:
Changes in appetite that result in weight losses or gains unrelated to dieting
Insomnia or oversleeping
Loss of energy or increased fatigue
Restlessness or irritability
Feelings of worthlessness or inappropriate guilt
Difficulty thinking, concentrating, or making decisions
Thoughts of death or suicide or attempts at suicide...
For many people, depression cannot always be controlled for any length of time simply by exercise, changing diet or taking a vacation. It is, however, among the most treatable of mental disorders: between 80% and 90% of people with depression eventually respond well to treatment, and almost all patients gain some relief from symptoms."
Bipolar Disorder (Manic Depression):
"Bipolar disorder, also commonly known as manic depression, is a brain disorder that causes shifts in a person's mood, energy, and ability to function.... Bipolar disorder can cause dramatic mood swings - from high and feeling on top of the world, or uncomfortably irritable and 'revved up,' to sad and hopeless, often with periods of normal moods in between....All depression symptoms are also common among those diagnosed with bi-polar disorder(s).
Because bipolar disorder is a recurrent illness, long-term preventive treatment is strongly recommended."
2005 - American Psychiatric Association (APA)