context: People who have schizophrenia may hear voices or see things that aren't real. But what happens inside the brain of someone who has schizophrenia? Scientists are working to understand that. They've found that people who have the disorder may be more likely to have glitches in their genes that may disrupt brain development. There's another key brain difference. Studies show that certain brain chemicals that control thinking, behavior, and emotions are either too active or not active enough in people with schizophrenia. Doctors also believe the brain loses tissue over time. And imaging tools, like PET scans and MRIs, show that people who have schizophrenia have less âgray matterâ -- the part of the brain that contains nerve cells -- over time. This research is helping efforts to develop better treatments for people who have this condition. Doctors don't know what causes schizophrenia. It could be passed down in families, but not everyone who has schizophrenia has a close relative (like a parent, brother, or sister) with the condition. Some researchers believe that problems with brain development may be partly responsible for schizophrenia. Others believe that inflammation in the brain may damage cells that are used for thinking and perception. Many other things could also play a role, including: Exposure to viruses before birth Malnutrition Use of mind-altering drugs like LSD or marijuana as a teenager Scientists don't know if these things trigger the disorder. But they do know that schizophrenia tends to show up in people around late adolescence or early adulthood. It usually causes a similar set of symptoms, but it can happen differently from person to person. Two brain chemicals, dopamine and glutamate, carry messages to cells along brain pathways that doctors believe control thinking, perception, and motivation. Dopamine gets a lot of attention in brain research because it's been linked to addiction. It also plays a role in other psychiatric and movement disorders, like Parkinson's disease. In schizophrenia, dopamine is tied to hallucinations and delusions. That's because brain areas that "run" on dopamine may become overactive. Antipsychotic drugs stop this. Glutamate is a chemical involved in the part of the brain that forms memories and helps us learn new things. It also tells parts of the brain what to do. One study found that people who are at risk for developing schizophrenia may have too much glutamate activity in certain areas of the brain at first. As the disease progresses, those brain areas may have too little glutamate activity. Doctors are working to find out how brain circuits that use these chemicals work together or are related to each other. Thanks to technology, doctors can see changes in specific areas of the brain. They can also map the possible loss of brain tissue. One study showed that brain tissue loss in young people at risk of developing the illness was linked to psychotic symptoms like hallucinations. Another study compared MRI pictures of the brains of youths about age 14 who had no symptoms of schizophrenia with those who did. It found that the teens who had symptoms lost more brain tissue over a 5-year period than the others. Research shows that adults who have schizophrenia also may lose gray matter. When we're just hanging out -- the dishes are done, we've finished our homework, or we've completed a tough project at work -- our thoughts are free to roam. This âdefault modeâ allows us time to daydream, reflect, and plan. It helps us to process our thoughts and memories. Scientists call this the default mode network. When we're not focused on a given task, it âlights up." If you have schizophrenia, your default mode network seems to be in overdrive. You may not be able to pay attention or remember information in this mode, one study shows. Researchers are working on new medications for the disorder. At least once tackles the glutamate factor. People with schizophrenia have also had some positive results using sarcosine, a chemical that is thought to regulate glutamate. But doctors aren't sure whether it could help over the long term. So although schizophrenia has no cure and sometimes may get worse over time, the right medications, combined with therapy, can help control the symptoms.