Prevalence

Prevalence rates for learning disorders vary, depending on the definitions
and methods of determining the achievement-intelligence discrepancy. According
to the American Psychiatric Association, estimates range from 2
percent to 10 percent for the general population, and 5 percent for public school students in the United States. The prevalence rate for each specific
learning disorder is more difficult to establish because many studies simply
report the total number of learning disorders without separating them according
to subcategory. Reading disorder is the most common, found in 4
percent of school-age children in the United States. Approximately four out
of five cases of LD have Reading Disorder alone or in combination with
Mathematics Disorder or Disorder of Written Expression. About 1 percent
of school-age children have Mathematics Disorder, one out of five cases of
LD. Disorder ofWritten Expression alone is rare; it is usually associated with
Reading Disorder.

Studies based on referrals to school psychologists or clinics reported that
more males than females manifested a learning disorder. However, studies
employing careful diagnostic assessment and strict application of the criteria
have found more equal rates for males and females. LD often coexists
with another disorder, usually language disorders, communication disorders,
attention-deficit hyperactivity disorder (ADHD), or conduct disorder. 495