A new study suggests that people with mental disorders are more likely to be left-handed. The German researchers compared data from over 200-thousand individuals and found people with schizophrenia, autism, and other neurodevelopmental disorders show higher rates of left-handedness compared to the general population. The study published in the Psychological Bulletin shows hand preferences often beginning even before birth, with prenatal thumb sucking at ten weeks of pregnancy being a good indicator of hand preference later in life.