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.
These breeds are essentially the same dogs but have been bred for different purposes and/or size standards since the mid 1930's. Some are even dual registered (i.e., registered as an American Pit Bull Terrier with the UKC and as an American Staffordshire Terrier with the AKC). Petey the Pup from The Little Rascals was among the first American Pit Bull Terriers to be registered with the AKC as an American Staffordshire Terrier.