Patients with psychotic diseases, such as schizophrenia, are more likely to be left-handed than individuals with other types of mental illness.
In a 2007 study conducted in the United Kingdom, researchers discovered that left-handed postmenopausal women had a greater breast cancer risk.
A 2001 British study indicated that lefties are more likely to develop autoimmune and inflammatory bowel disorders like Crohn's disease.
A Harvard study found that left-handed women had a 62% higher risk of MS than right-handed women.
In a 2011 University of Toledo study of sleep-clinic patients, 94% of lefties had limb movements on both sides while sleeping.
According to a research published in Pediatrics, mixed-handed children are more likely to suffer language, academic, and mental health issues.
Lefties had 10 to 12 percentage points lower annual incomes than righties, which visible disparities can partially explain in cognitive abilities & behavioral issues.
Yes, either left-handed people will be extremely introverted or extremely extroverted. And the mix handers will be even more.