There are actually many causes of canine depression including moving to a new house, the loss of another pet, the loss of a family member, a sudden increase in time that the dog is left home alone
, a decrease in exercise (a depressed mood can develop after approximately 2 weeks of inactivity) and even SAD (Seasonal Affective Disorder).
Being scared -
Feeling frightened is a frequent cause of acute tail problems. With a high tail set, this breed cannot really ‘tuck the tail between the legs’; so, if a Shih Tzu is afraid he may hold it lower than normal. It may curve over too far and touch the back or it may droop low off of the body.
Any sort of trauma to any part of the tail can cause a dog to carry it at an odd angle. The dog may also not wish to move the tail (due to pain) or may not be able to move it (due to internal damage).
A person accidentally stepping on the tail is by far the most common reason for tail trauma; however, there is a wide range of possible causes. Anything from rough play with another dog to being handled incorrectly to thumping it repeatedly on a hard surface to having it caught in something (car door, snagged on gate, etc.). See ahead for tail trauma treatment.
Anal gland issues –
Every dog has a pair of anal glands, also referred to as scent glands, with one located on each side of the anal opening. These hold an oil that is secreted in very small amounts each time that a dog has a bowel movement and also any time that the dog comes into contact with another dog.
Sometimes these glands can become filled with too much fluid (engorged) or the fluid can develop into a thick paste-like substance (impacted). If either of these issues develop, it can cause a Shih Tzu to feel very uncomfortable and in turn, hold his tail funny, have trouble wagging it, or resist moving it.
Back problems –
Less common but still a possibility is an issue with the back. The tail is an extension of the spine and therefore something such as a ruptured disk will often radiate pain down to the tail.
In many cases a Shih Tzu with back pain will sit at an odd angle, having trouble walking, may limp, will not be able to exercise
as normal, and will show other signs of discomfort; however, even without these other symptoms most veterinarians will examine the back when the tail appears injured.
Age related issues -
As dogs age there may be problems with posture. This can be due to arthritis, though most older dogs also have weaken tendons and decreased muscle that can cause the tail to not be held as high as their younger counterparts.