Paranoia, hallucinations and schizophrenia are all words that people associate with mental illness. In David Auburn's Proof, characters display these signs and more. Mental illness is a combination of environmental and hereditary factors that can affect a person at any stage of life. Catherine and Robert appear to show signs of mental illness from her talking to her father after he progresses to graphomania and Robert's hallucinations. Mental illness is a theme that resonates throughout Proof. Mental illness is a debilitating illness that affects characters' mental stability and sanity. Mental illness is something that people don't like to talk about due to the stigma associated with it. Mental illness is a common, but misunderstood, medical condition that changes cognitive, mental and social abilities. Some common mental illnesses include depression, obsessive-compulsive disorder, bipolar disorder, and schizophrenia. These diseases and disorders can affect multiple parts of a person's personality and change their mental capacity. Some of the main causes of mental illness are genetic, traumatic and environmental. Genetic mental illness is contained in a person's genetics and travels through genes. This mental illness travels from parents to children. Traumatic mental illnesses, such as post-traumatic stress disorder, affect many people but are common among military service men and women. Traumatic events can alter the way the brain works. Anxiety, insomnia and anger are common symptoms of this trauma. These changes to the brain are not permanent, and with therapy and treatment, the damage is reversible. Environmental mental illness is a very common mental illness with links to environmental factors such as drugs...... middle of paper ......red, Catherine's mental instability is due to copious amounts of stress a to which she is subjected and she is working to prove that she is a good mathematician like her father. Mental illness is a debilitating illness that can devastate a person and their family. Mental illness is also a major theme in Proof, and readers see the main characters show signs of mental illness. Robert's mental illness, although never revealed, affects his mind and the way he thinks. Catherine, on the other hand, may not have a mental illness problem, but rather a problem with too much stress. Catherine is forced to care for her father and live up to his legacy. This stress is enough to affect long-term mental stability and can change the way a person's brain works. Stress on Catherine could manifest itself in a state of mental illness.