Specific learning disorder is frequently but not invariably preceded, in preschool years, by delays in attention, language, or motor skills that may persist and co-occur with specific learning disorder. An uneven profile of abilities is common, such as above-average abili- ties in drawing, design, and other visuospatial abilities, but slow, effortful, and inaccurate reading and poor reading comprehension and written expression. Individuals with spe- logical tests of cognitive processing. However, it remains unclear whether these cognitive abnormalities are the cause, correlate, or consequence of the learning difficulties. Also, al- though cognitive deficits associated with difficulties learning to read words are well doc- umented, those associated with other manifestations of specific learning disorder (e.g., reading comprehension, arithmetic computation, written expression) are underspecified or unknown. Moreover, individuals with similar behavioral symptoms or test scores are found to have a variety of cognitive deficits, and many of these processing deficits are also found in other neurodevelopmental disorders (e.g., attention-deficit/hyperactivity disor- der [ADHD], autistic spectrum disorder, communication disorders, developmental coor- dination disorder). Thus, assessment of cognitive processing deficits is not required for diagnostic assessment. Specific learning disorder is associated with increased risk for sui- cidal ideation and suicide attempts in children, adolescents, and adults.
There are no known biological markers of specific learning disorder. As a group, indi- viduals with the disorder show circumscribed alterations in cognitive processing and brain structure and function. Genetic differences are also evident at the group level. But cognitive testing, neuroimaging, or genetic testing are not useful for diagnosis at this time.
The prevalence of specific learning disorder across the academic domains of reading, writ- ing, and mathematics is 5%—15% among school—age children across different languages and cultures. Prevalence in adults is unknown but appears to be approximately 4%.
Onset, recognition, and diagnosis of specific learning disorder usually occurs during the elementary school years when children are required to learn to read, spell, write, and learn mathematics. However, precursors such as language delays or deficits, difficulties in rhyming or couhting, or difficulties with fine motor skills required for writing commonly occur in early childhood before the start of formal schooling. Manifestations may be be- havioral (e.g., a reluctance to engage in learning; oppositional behavior). Specific learning disorder is lifelong, but the course and clinical expression are variable, in part depending on the interactions among the task demands of the environment, the range and severity of the individual’s learning difficulties, the individual’s learning abilities, comorbidity, and the available support systems and intervention. Nonetheless, problems with reading ﬂu- ency and comprehension, spelling, written expression, and numeracy skills in everyday life typically persist into adulthood.
Changes in manifestation of symptoms occur with age, so that an individual may have a persistent or shifting array of learning difficulties across the lifespan.
Examples of symptoms that may be observed among preschool-age children include a lack of interest in playing games with language sounds (e.g., repetition, rhyming), and they may have trouble learning nursery rhymes. Preschool children with specific learning disorder may frequently use baby talk, rnispronounce words, and have trouble remembering names of let- ters, numbers, or days of the week. They may fail to recognize letters in their own names and have trouble learning to count. Kindergarten—age children with specific learning disorder may be unable to recognize and write letters, may be unable to write their own names, or may use invented spelling. They may have trouble breaking down spoken words into syllables (e.g., ”cowboy” into ”cow" and ”boy”) and trouble recognizing words that rhyme (e.g., cat, bat, hat).
Kindergarten-age children also may have trouble connecting letters with their sounds (e.g., let- ter b makes the sound / b / ) and may be unable to recognize phonemes (e.g., do not know which in a set of words [e.g., dog, man, car] starts with the same sound as ”cat”).