There was an explosion of dyslexia diagnoses in California when the state implemented a systematic whole language curriculum. The article also mentions that there is a high correlation between dyslexia and ADHD. 75% of children diagnosed with ADHD are dyslexic.
This link explores the link between sound recognition, phonemes and brain activity.
It is not uncommon to find a family where one child has ADHD, another dyslexia or learning difficulties, a third dyspraxia and it is quite common for an individual to suffer from more than one of these conditions. In fact:* "As many as 65% of children with ADHD also struggle with at least one other learning disorder, and sometimes bipolar disorder and/or Tourette’s Syndrome (TS) [14]
* 50% of dyspraxic children also have ADHD [14]
* Some 30 to 50 percent of children with dyslexia have ADHD and vice versa. (The Dyslexia Research Institute puts this figure at 60%)" [14]
* It is estimated that 60% of people with Tourette’s Syndrome (TS) have ADHD and 50% have Obsessive Compulsive Disorder (OCD) and that there is a high association of these disorders in their family histories [15].