Schizophrenia is a chronic, severe, and disabling brain disorder that is often misrepresented in popular culture. Rather than the murderous, dangerous individuals characterized by countless movies, those suffering from this condition may be frightened and withdrawn. While schizophrenia can tend to run in families, there are many other factors, both proven and suspected, that also contribute to one's chances of developing this condition.

Left-Handed People

Yale researcher Jadon Webb and his colleagues found there may be a link between being left-handed and chances of developing schizophrenia, Medical Daily reported. The team found that those who are left-handed are not only more likely to develop schizophrenia than their right-handed counterparts, but also more likely to develop other psychotic disorders, such as depression and bipolar disorder. According to a Yale University press release, 40 percent of people with schizophrenia or schizoaffective disorders are left-handed. When taking into consideration that only 10 percent of the U.S. population is left-handed, this discrepancy is quite remarkable.

City Dwellers

According to information provided by About Health, black Americans are 1.5 times more likely to develop schizophrenia than white Americans. Although scientists at first believed this discrepancy was race related, it was later discovered that the mental illness link was not due to the individual’s race but more where they were raised. “The incidence for schizophrenia is almost doubled for individuals who are born and brought up in cities,” concluded Dr. Jens Pruessner, who wrote a study on the subject in 2011.

Moving into an urban area later in life was not correlated with increased risk for schizophrenia. Although the exact reason for this is unclear, researchers believe it is because different regions of the brain are sensitive to the experience of city living during different times in one’s life, according to a press release.

Pale People

OK, so it’s not exactly having a fair complexion that puts people at risk for schizophrenia, but rather a deficiency in the sunshine vitamin, vitamin D, Medical Daily reported. Recently, researchers from the Isfahan University of Medical Sciences in Iran found that vitamin D-deficient individuals are twice as likely to be diagnosed with schizophrenia as people who have sufficient amounts of the vitamin, according to a press release. While the team’s findings were strong enough to support the link between low levels of vitamin D and schizophrenia, Ahmad Esmaillzadeh, one of the researchers in the study, explained that “[m]ore research is needed to determine how the growing problem of vitamin D deficiency may be affecting our overall health.”

Children Of Stressful Pregnancies

Studies have shown that children of women who experienced a degree of famine during the first three months of their pregnancy are more likely to develop schizophrenia. Other pregnancy complications, such as bleeding during pregnancy, gestational diabetes, and preeclampsia have also been linked to high levels of schizophrenia. Fetuses that experience abnormal growth in the womb, have been exposed to a virus in vitro, or experienced a serious lack of oxygen during birth may be more likely to develop the mental condition later on in life.

However, it should be noted that although these pregnancy and birth complications are associated with higher risk for schizophrenia, experiencing them is not a definite determining factor.

Teens Who Smoke Pot

While marijuana and other drugs are not the cause of schizophrenia, they can trigger the condition in an already predisposed mind. According the the UK’s National Health Service, teenagers under 15 who regularly smoke marijuana are up to four times more likely to develop schizophrenia by the age of 26. Certain drugs can trigger the condition's symptoms and even cause a relapse in people who are recovering from an earlier episode.

People With Winter Birthdays

It has been observed that schizophrenia is more widespread among individuals born during the winter, with January marking the highest number of schizophrenia birthdays. This connection is more likely during the increased chance of risky pregnancies during the winter and less to do with being born under a certain star sign, however. For example, mothers are more likely to contract illnesses such as the flu during winter months, which can complicate childbirth.

“This is further confirmation of seasonal variations in births of those later diagnosed with mental diseases,” said William Grant at the Sunlight, Nutrition, and Health Research Center at San Francisco, to Psych Central.