Did you know? A study published in the Journal of Small Animal Practice, found that dogs who chased their tail had significantly higher HDL and LDL levels, known in people as good and bad cholesterol. The theory behind this is that high levels of cholesterol affect the flow of hormones, such as serotonin. There hormones play an important role in mood and behavior, making affected dogs more prone to obsessive behaviors. https://www.ncbi.nlm.nih.gov/pubmed/19261083