Anxiety disorders all generate their own skewed reality, both as a symptom and as a result of what anxiety is. Most people who suffer from anxiety are unaware of how frequently worry alters their thinking. This is due to the fact that the human brain and cognition are more sophisticated than they appear. It is estimated that up to 40% of adults experience some form of anxiety at some point in their lives. Anxiety can be described as a feeling of unease or dread that affects the body's ability to function properly. People may have panic attacks, feel shaky, sweaty, nauseous, or have abdominal pain. Anxiety can also affect one's appetite or sleep pattern. It is not just humans who suffer from anxiety; it has been reported across many species including dogs, cats, horses, and even monkeys. There are several types of anxiety disorders. They include social anxiety disorder, generalized anxiety disorder, obsessive-compulsive disorder, post-traumatic stress disorder, and substance-induced anxiety. The main thing that ties these disorders together is that they all involve some degree of anxiety or fear. People with anxiety often have a very distorted view of life. They tend to believe that things will be worse than they actually are, that negative events will definitely happen, and that if they just kept trying hard enough something bad would always happen.