To be diagnosed as a learning disability, specific criteria must be met. Causes Mental health professionals stress that that the cause of learning disabilities is unknown, and there are too many possibilities to pin down the cause of the disability with certainty. Once thought to be caused by a single neurological problem, researchers now say that the causes are more diverse and complex. New evidence seems to show that most learning disabilities do not start in a single, specific area of the brain, but from difficulties in bringing together information from various brain regions. A leading theory is that learning disabilities stem from subtle disturbances in brain structures and functions.
Some scientists believe that, in many cases, the disturbance begins before birth.
By law, learning disability is defined as a significant gap between a person's intelligence and the skills the person has achieved at each age. Actual diagnosis of learning disabilities is made using standardized tests that compare the child's level of ability to what is considered normal development for a person of that age and intelligence. Learning disorders may be informally flagged by observing significant delays in the child's skill development. A two-year delay in the primary grades is usually considered significant. For older students, such a delay is not as debilitating, so learning disabilities aren't usually suspected unless there is more than a two-year delay.