The following diagram displays the increased relative risk (or "odds ratio") that is associated with some of the more well-researched environmental factors (family history/genetics is included for comparison) that have been linked with schizophrenia. In this diagram, the "odds ratio" represents the relative increase in risk associated with schizophrenia, where a "1" is average. So, a child born during the winter months (January through March/April, in the Northern hemisphere) has about a 10% higher risk of schizophrenia than average. A person born in an urban environment has about a 50% (with an odds ratio of ) higher risk of developing schizophrenia. A child born from a mother who has Rubella has about a 500% increased risk of schizophrenia, etc. The "family history" odds ratio identified below is actually much more difficult to estimate than the number below suggests - it depends upon (as mentioned in the genetic factors above) the level of interelatedness of the family member who had schizophrenia, and other brain disorders in the family. To get an accurate reading on this for any individual it is best to talk with a genetic counselor .