Simplify the following text for a Grade 11 native English-speaking person.
Original: Though past research showed no correlation between attention-deficit hyperactivity disorder ( ADHD ) and food dyes , new studies now point to synthetic preservatives and artificial coloring agents as aggravating ADD and ADHD symptoms , both in those affected by these disorders and in the general population .
Simplified: In the past , research has not shown any link between Attention Deficit Hyperactivity Disorder and food dyes . Newer studies show that synthetic preservatives and artificial coloring agents can make the syptoms of ADD and ADHD worse .