Depression in dogs is often the result of a constant or traumatic stress in their environment. Intense or distressing interactions with other animals, physical injuries and infections are among the most common causes of canine depression. Depression manifests itself in a number of symptoms that vary significantly between individual dogs. Not every dog's symptoms will be the same, but there are several key side effects of depression that are found in the majority of canine depression cases. Always consult an experienced veterinarian regarding the health and treatment of your pet.
Observe your dog's behavior throughout the day. Watch him when he eats, sleeps, plays and grooms. A distinct change in his basic habits, like cleaning or playing, or disposition towards humans and animals is a key symptom of depression. If your normally engaging and playful dog suddenly begins to spend most of his time sleeping, then he may be suffering from a case of depression. If you notice unusual activity, continue to monitor your pet for several days to see if the behavior continues or if it is only temporary. Short-term behavioral changes aren't uncommon in dogs, and they don't necessarily represent a long-term disorder.
Feed your dog throughout the day and watch to make sure he eats it. Depressed dogs often eat far less than they normally do. They may spend some time playing with their food, but not ingesting it. This semi-starvation can develop into a physical fitness problem if it continues for weeks or months. If you have recently switched the brand or type of dog food, try feeding him some of the old variety. If he is still unwilling to eat, or if he continues to eat less than normal, then there is a good chance he is physically or mentally distressed.
Hold your dog still and look for signs of injury. Bruises, cuts, punctures and other wounds may leave your dog in constant pain for days or weeks, which often leads to temporary depression. The behavioral changes often fade as the injury heals, so treating the wound is the priority. Look for bruised skin, ripped hair or blood. Watch for signs of pain when your dog is eating or walking. Bone and tooth problems pose a long-term and consistently painful problem for your pet.
Look for other possible causes for the changes in your dog's behavior if he shows no signs of physical injury. He could be sick with a bacterial or viral illness, or he may be experiencing severe emotional stress. Some ailments, like Lyme disease, consistently cause depression or similar conditions. If your dog has ocular or nasal congestion or has trouble breathing, then he may have contracted an infectious disease. The death of another pet or a sudden change in environment can disrupt your dog's routine, which causes mental stress. Consult a veterinarian or dog specialist if you cannot determine the cause of your dog's depression, or if his mood does not improve within a few days.