Abnormal psychology is often used to understand or to treat people with mental disorders to make life better for them. This is because abnormal behaviour is often defined as when someone is not able to change how they behave to fit different settings. This is often also used to define some mental disorders. When someone cannot change their behaviour to fit the people and situations around them when they need to, it can cause suffering, and the person may be uncomfortable when around people. Their behaviour can be unreasonable and hard to understand. Their behaviour can even be dangerous.