Asperger syndrome cannot be found by testing blood or looking at someone's body. A medical doctor needs to talk with the person and other people who know him or her well, to watch how the person moves and behaves, and to learn about the person's past. Sometimes a doctor believes by mistake that the person has schizophrenia, obsessive-compulsive disorder, ADHD, or mental retardation instead. Tourette syndrome with "tics" (repetitive, uncontrolled actions like twitching, blinking, and coughing) sometimes comes with Asperger syndrome. Many people with Asperger syndrome also have ADHD and/or OCD. It has been estimated that beyond half of the people with the syndrome, also carry some other type of syndrome, disorder, disability, disease, or illness. The MSD Manual says "strong evidence supports a genetic component".