In life, most people experience headaches. Headaches are caused by diseases in the brain, but there are exceptions. Diseases of the organs adjacent to the brain, diseases of organs far away from the brain, and systemic diseases can also cause headaches. From this we can infer:. ['Most people have brain disease.', 'Diseases in one part of the body sometimes cause pain in other parts.', 'When a person has a disease near the brain.', 'The human head is more susceptible to disease than other parts of the body.']