Simplify the following text for a Grade 11 native English-speaking person.
Original: A German study has shown that 1 â `` 2 % of the population meet all the diagnostic criteria of BDD , with a larger percentage showing milder symptoms of the disorder ( Psychological Medicine , vol . 36 , p. 877 ) .
Simplified: A German study has shown that 1-2 % of the population has complete BDD , but a bigger percentage of people show some of the effects ( Psychological Medicine , vol 36 , p 877 ) .