Comorbidity in Specific Learning Disorder: Issues in Assessment

Specific learning disorder (SLD) is a developmental disorder associated with lower than age-expected educational skills (reading, writing, and mathematics) leading to significant problems with scholastic performance.1 Childhood psychiatric disorders have high comorbidity, and SLD is no exception. The comorbidity in SLD needs to be carefully evaluated and managed, as it leads to significant functional impairment, complicates the clinical picture, and worsens the prognosis.2

In this context, in a study published in this journal3 on 7 to 12 years old children with SLD-mixed type, the investigators used Mini International Neuropsychiatric Interview for Children and Adolescents4 to diagnose psychiatric disorders and Child Behavior Checklist (CBCL)5 to “assess social competence and behavior problems,” while, Conner’s 3TM Parent Short form6 was used “to identify attention deficit/hyperactivity disorder (ADHD) and common comorbid problems.” Sixty-one percent of their sample had signs of attention deficit disorder; social anxiety was found in one subject, while another child had oppositional defiant disorder and attention deficit disorder. The authors also reported difficulties in executive function, peer relations, and aggression in their sample of SLD.

For assessing learning and psychiatric disorders, when available, use of culture-fair/free and locally standardized instruments should be used. For the Indian population, National Institute of Mental Health and Neurological Sciences (NIMHANS) Index for SLD7 is standardized and recom-mended.8 Developmental Psychopathology Check List (DPCL)9 is a tool validated against CBCL,5 to screen for childhood psychopathology in the Indian setting. In school-going Indian children aged between 6 and 12 years, Bandla et al10 used NIMHANS Index7 to confirm the diagnosis of SLD and DPCL9 to assess comorbidity. The prevalence of SLD was 6.68%, the combined (mixed) type being the most common. ADHD was the most common comorbidity (41.9%), mostly inattentive subtype; other disorders were conduct and emotional disorders.

Altay and Görker11 reported high psychiatric comorbidity (92.5%) in their sample of SLD cases aged between 6 and 15 years. The most frequent disorder was ADHD (82.3%), followed by specific phobia, oppositional defiant disorder, enuresis, and tic disorders. Among the subtypes, the combined type of SLD (reading, writing, and math disorder) was the commonest one (37.5%). Those with “math disorder” had lower intelligence level and higher psychiatric comorbidity.

High comorbidity (7–92%) of SLD and ADHD in various studies12 is a subject of particular interest and attributed to common neuropsychological and genetic risk factors.13 It remains to be seen whether other comorbidities also have similar underpinnings.