It's not just serotonin either-most neurotransmitters can cause anxiety or anxiety like symptoms, and in some cases an over-abundance of a chemical can lead to anxiety. So it does appear that you can develop it without experiencing a stressful life.
Howard Heinzl (1918 - 1989) With regard to blue American Staffordshire Terriers, any breeder that believes that a blue American Staffordshire Terrier is some how more valuable than the other recognized colours, is not only deceiving themselves, but they are also deceiving their customers.
Cole miners in England bred the Staffordshire bull terrier because they needed a fast, small working dog. The Staffordshire is the shortest and lightest of the three breeds for this reason. They stand 14 to 16 inches tall and typically weigh 24 to 38 pounds.