Doctors and researchers have been able to identify the causes of a variety of medical conditions, such as the common cold, a heart attack, and gout, to name a few. For example, there are different types of viruses that cause the symptoms of a common cold. By knowing what causes a medical problem, doctors are able to treat the condition in the most focused way possible. In the previous chapter, three general categories of causes of psychosis were presented: medical causes, substances, including certain drugs of abuse and several medicines, and a number of psychiatric illnesses. This chapter presents what is currently known about the causes of the third of these, psychiatric illnesses, especially primary psychotic disorders like schizophrenia. Some health conditions have a single, straight-forward cause. As mentioned earlier, a common cold is caused by a virus. However, many illnesses do not have a single identifiable cause. Rather, they are caused by a combination of risk factors. A risk factor is any event, exposure, or entity that occurs before the illness and that research has shown plays a role in causing the illness. For example, cigarette smoking is a well-known risk factor for lung cancer. Smoking occurs before the lung cancer develops, and researchers have proven that smoking cigarettes plays a part in causing many cases of lung cancer. Because schizophrenia and related psychotic disorders are such complex illnesses, it is sometimes unclear if some of the risk factors truly occur before the illness. Some risk factors may make some people more psychosis-prone. In other words, some risk factors are best thought of as increasing one’s tendency towards psychosis rather than actually causing psychosis. Over the past several decades, researchers have identified some of the likely causes of complex medical conditions like diabetes, high blood pressure, and psychosis. For each of these, as is true of most medical conditions, there is no single cause. Rather, a number of risk factors, both internal (like certain genes) and external (like exposures that stress the body, such as stressful life events or drugs) combine in complex ways to bring about the illness.
Lung cancer in the Indian subcontinent
