context: If you know someone with schizophrenia, you probably want to know why they have it. The truth is, doctors don't know what causes this mental illness. Research shows it takes a combination of genetics and your environment to trigger the disease. Knowing what increases the chances can help you put together a better picture of your odds of getting schizophrenia. Think of your genes as a blueprint for your body. If there's a change to these instructions, it can sometimes increase your odds for developing diseases like schizophrenia. Doctors don't think there's just one âschizophrenia gene.â Instead, they think it takes many genetic changes, or mutations, to raise your chances of having the mental illness. They do know that you're more likely to get schizophrenia if someone in your family has it. If it's a parent, brother, or sister, your chances go up by 10%. If both your parents have it, you have a 40% chance of getting it. Your chances are greatest -- 50% -- if you have an identical twin with the disorder. But some people with schizophrenia have no history of it in their family. Scientists think that in these cases, a gene may have changed and made the condition more likely. Many genes play a role in your odds of getting schizophrenia. A change to any of them can do it. But usually it's several small changes that add up and lead to a higher risk. Doctors aren't sure how genetic changes lead to schizophrenia. Genetic changes can interact with things in your environment to boost your odds of getting schizophrenia. If you were exposed to certain viral infections before you were born, research suggests that your chances may go up. This could also be true if you didn't get proper nutrition while your mother was pregnant with you, especially during her first 6 months of pregnancy. These are both theories, but they haven't been proven by scientific studies. Studies show that taking certain mind-altering drugs called psychoactive or psychotropic drugs, such as methamphetamine or LSD, can make you more likely to get schizophrenia. Some research has shown that marijuana use has a similar risk. The younger you start and the more often you use these drugs, the more likely you are to have symptoms like hallucinations, delusions, inappropriate emotions, and trouble thinking clearly. Scientists are looking at possible differences in brain structure and function in people with and people without schizophrenia. In people with schizophrenia, they found: Spaces in the brain, called ventricles, were larger. Parts of the brain that deal with memory, known as the medial temporal lobes, were smaller. There were fewer connections between brain cells. People with schizophrenia also tend to have differences in the brain chemicals called neurotransmitters. These control communication within the brain. Studies of brain tissue in people with schizophrenia after death even show that their brain structure is often different than it was at birth. An older father Problems with your immune system, like inflammation or an autoimmune disease Taking mind-altering drugs as a teen Complications during pregnancy or birth such as: Low birth weight Premature labor Exposure to toxins, bacteria, or viruses Lack of oxygen during birth Living in a low-income urban area