Separation Anxiety
(article) Anxiety is a very real condition for many dogs and cats especially those who have been rescued or traumatized. "Separation Anxiety" is considered by many experts to be a chemical imbalance or mental illness. Symptoms include excessive destruction of property, fear, nervousness and hyperactivity upon departure of a pet's owner.
Health Tip- There exist many effective training or desensitization techniques which can be utilized to relieve/reduce anxiety. These include crate training and pet owner training. Anxiety/calming supplements can be used in conjunction with training to reduce the symptoms of Separation Anxiety. Some experts suggest diet also plays a role in chemical imbalances and that proper nutrition should be a priority. This very difficult condition can often be managed with patience and consistency.

Mental Health
(article) As with physical health, mental health should be a focus for pet owners. Many situations can cause stress and anxiety and change your pet's behavior. Symptoms of a stressed dog/cat include panting, pacing, barking, and hiding.
Health Tip- Know what causes stress in your pet and consider your pet's reactions before potentially traumatic events such as fireworks, thunderstorms, travel, and separation. Understanding that pets can feel pain, anxiety and other "human" emotions can help keep your pet happy and healthy.