By Dr. Sanchari Sinha Dutta, Ph.D. Reviewed by Lauren Hardaker Feb 3 2026 By comparing identical twins, researchers uncover why working for yourself may come with hidden stress costs, but why long hours matter more than job variety. Study: Does self-employment increase stress? A co-twin control analysis of Finnish and US twins . Image credit: gpointstudio/Shutterstock.com A recent study of identical twins from Finland and the United States finds that self-employment is associated with higher