Suppose a person has an IQ of 130, as measured by a standard IQ test, when he is 18 years old. He then goes on to develop severe mental illness, which reduces his IQ to 100. After this, he takes a DNA-intelligence test, like the one offered by GenePlaza, which claims to measure his intelligence from his DNA. Will this test show an IQ closer to 130 or 100?
Note that mental illness is governed by a combination of genetic and environmental factors.