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.
This is a red fawn Boxer. As you can see, this fawn is darker and deeper than that the common tan fawn; producing a slight shading of red. What a gorgeous coat. This Boxer is a dark brindle. As you can see, with dark brindle the black is over powering the fawn color. The black striping in this pattern is heavy; which would be called a reverse or even a seal. If a Boxer has more than 1/3 of white on his body, the dog will be classified as Parti-color.