72 Neurodevelopmental Disorders
avoid activities that demand reading or arit hmetic (reading for pl easure, reading instruc-
tions). Adults with specific learning disord er have ongoing spelling problems, slow and
effortful reading, or problems making impo rtant inferences from numerical information
in work-related written documents. They ma y avoid both leisure and work-related activ-
ities that demand reading or writing or use alternative approaches to access print (e.g.,
text-to-speech/speech-to-text softwa re, audiobooks, audiovisual media).
An alternative clinical expression is that of  circumscribed learning difficulties that per-
sist across the lifespan, such as an inability to master the basic sense of number (e.g., to
know which of a pair of number s or dots represents the larger magnitude), or lack of pro-
ficiency in word identification or spelling. Av oidance of or reluctance to engage in activi-
ties requiring academic skills is common in ch ildren, adolescents, and adults. Episodes of
severe anxiety or anxiety disorders, including somatic complaints or panic attacks, are
common across the lifespan and accompany both the circumscribed and the broader ex-
pression of learning difficulties.
Risk and Prognostic Factors 
Environmental. Prematurity or very low birth weight increases the risk for specific
learning disorder, as does pr enatal exposure to nicotine.
Genetic and physiological. Specific learning disorder a ppears to aggregate in families,
particularly when affecting reading, mathemat ics, and spelling. The relative risk of spe-
cific learning disorder in reading or mathematics is substantially higher (e.g., 4–8 times
and 5–10 times higher, respectively) in first- degree relatives of individuals with these
learning difficulties compared with those wi thout them. Family hist ory of reading diffi-