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.
After dog fighting was banned in the United States in 1900, two strains of these dogs were developed, a show strain and a non-show strain. The show strain was labeled the American Staffordshire, while the non-show dog strain was labeled the American Pit Bull Terrier.