Chronic stress
Stress is a normal part of every living thing's daily life.  However, when stress becomes chronic, it can damage the body and the mind.  When a person (or animal) is stressed, the body reacts in certain ways - for example, by releasing chemicals called corticosteroids.  If this happens again and again, over a long period of time, it can change the way the brain works. These changes can damage working memory spatial memory, and decision-making skills. They can also increase aggression.