Marfan syndrome does not affect IQ. On the contrary, people with Marfan syndrome tend to have above average intelligence. A study found that the average IQ of people with Marfans is 109.3, significantly higher than other people.
85
Technically, it's a developmental illness, but basically, yes. Down syndrome is caused by a defection in the chromosomes in a person. It happens when a third 21st chromosome is copied. It causes the person to develop slower mentally and physically. There are other problems that often accompany Down syndrome, such as hip dysplasia. This is when the person has a too shallow socket on their pelvic bone and the ball on their femur often slips out of the socket, causing it to dislocate. This can be incredibly painful, but, sometimes, the person can't feel anything. [My sister has Down syndrome]
The average IQ of a person in the US is around 98. IQ scores are standardized to have a mean of 100 and a standard deviation of 15.
The average IQ of a person in India is estimated to be around 82.
the average IQ of a british person is 84
The average adult IQ in the UK is 100
A child with Asperger's Syndrome can be a child with a high IQ. People with Asperger's Syndrome typically have average to high IQs.
I think it would be unlikely that Asperger's Syndrome (AS) would be misidentified as high IQ; however, a person with Asperger's Syndrome might also have a high IQ. A person with AS will have various symptoms, some of which might cause a misdiagnosis of an attention deficit disorder (ADD or ADHD), obsessive-compulsive disorder (OCD), a learning disability, or other conditions. As an example, it seems unlikely that a medical professional would explain rarely speaking, an intense interest in doorknobs, lack of eye contact, or experiencing extreme anxiety when lights flash as having a high IQ. A person can have both Asperger's Syndrome and a high IQ, only Asperger's Syndrome, or only a high IQ. Some people with Asperger's Syndrome have a high IQ. Most people with a high IQ do not have Asperger's Syndrome.
A high functioning DS can have an IQ in the 60's most are quite a bit lower.
Age has nothing to do with IQ. An average IQ is 100, no matter what age a person is.
An average person's IQ is 100; 75 percent of the population has an IQ higher than 90. 87 IQ is considered "low average."