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.
The Boxer does not carry the gene for a solid black coat color and therefore purebred black Boxers do not exist. 1  The colour brindle can be with or without white markings. 2  A red fawn boxer.  3 Reverse brindle Boxer, cropped and docked.