Why is it not totally surprising that animals can suffer from emotional distress or mental illness?

Animals also appear to suffer from emotional distress or mental illness. Whether they are animals in circuses or are kept in ill-managed zoos, or whether they are pets, they can become extremely anxious, sad, or even traumatized.  

The psychological illness is basically considered as a specific human trait, however, it has been demonstrated that various animals can agonize from mental health issues like those witnessed in humans. These animals can even help one to understand the reason behind human mental illness, and the evolution of these debilitating disorders.  

It has been observed that animal mental illness can be instigated by several of the similar elements, which can cause mental illness in humans. This comprises the loss of freedom, the loss of companions or family, trauma, stress, and abuse.