Researchers found links between family position and the risk of 150 health conditions, including autism, ADHD, allergies and digestive disorders. Firstborn children were more likely to develop a range of neurodevelopmental conditions, including autism, ADHD, Tourette's syndrome and obsessive-compulsive disorder (OCD). They also had higher rates of food allergies, hay fever, asthma and acne than their younger siblings. The findings come just months after another study suggested younger siblings really do have it easier. As a result, younger siblings spent more time using digital devices and less time on enrichment activities such as reading, music and homework than first-borns.