Learning disorders (LDs) are defined by significant academic underachievement that is unexpected based on an individual's age, cognitive ability, and education (e.g., American Psychiatric Association, 2000
). The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 2000
) provides diagnostic criteria for Reading Disorder (RD), Math Disorder (MD), and Disorder of Written Expression. In addition to these DSM-IV categories, other authors described non-verbal learning disability (NVLD), a syndrome characterized by specific difficulties in mathematics and spatial functioning, along with impairments in social cognition similar to the difficulties exhibited by individuals with pervasive developmental disorders (PDD; e.g., Klin, Volkmar, Sparrow, Cicchetti, & Rourke, 1995
; Rourke, 1989
LDs are associated with a range of negative outcomes and significant publich health costs. Prevalence estimates suggest that 5–15% of the population meet criteria for at least one LD (e.g., American Psychiatric Association, 2000
; Gross-Tsur, Manor, & Shalev, 1996
; Rutter et al., 2004
; Shaywitz, Shaywitz, Fletcher, & Escobar, 1990
), and over half of all students who receive special education services are identified due to an LD (e.g., Schnoes, Reid, Wagner, & Marder, 2006
). Studies that compared groups with and without an LD found that individuals with an LD experience greater academic difficulties, report lower motivation and greater frustration and distress in school, are more likely to drop out of high school prior to graduation, and reach lower levels of educational and occupational attainment as adults (e.g., Boetsch, Green, & Pennington, 1996
; Daniel et al., 2006
; Goldston et al., 2007
; McGee, Prior, Willams, Smart, & Sanson, 2002
; Willcutt et al., 2007
). LDs also co-occur more often than expected by chance with one another and with other disorders such as attention-deficit/hyperactivity disorder (ADHD), conduct disorder, anxiety disorders, and depression (Antshel & Khan, 2008
; Daniel et al., 2006
; Maughan, Rowe, Loeber, & Stouthamer-Loeber, 2003
; McGee et al., 2002
; Semrud-Clikeman et al., 1992
; Trzesniewski, Moffitt, Caspi, Taylor, & Maughan, 2006
; Willcutt et al., 2007
; Willcutt & Pennington, 2000a
; Willcutt & Pennington, 2000b
The high prevalence of LDs and their frequent co-occurrence with other disorders suggests that LD assessment measures should be systematically included in clinical assessment batteries and research studies focusing on developmental disorders. However, a full LD assessment requires the administration of standardized tests of academic achievement and cognitive ability by a trained examiner in a one-on-one testing session that typically lasts several hours. It is not feasible to complete such an extensive evaluation as part of many clinical assessments and research studies, particularly if comorbid learning difficulties are not the primary referral question for a clinical assessment or are a secondary aim of a study focusing on a related but separate topic.
Similar challenges are faced by clinicians or researchers who wish to screen systematically for a range of psychopathology as part of a standard clinical assessment battery or research protocol, as it is often unrealistic to devote the time necessary to obtain a comprehensive assessment of all relevant disorders. To address this issue, several screening measures for developmental psychopathology have been developed, such as the Achenbach System of Empirically Based Assessment (ASEBA; Achenbach & Rescorla, 2001
), the Behavior Assessment System for Children (BASC; Reynolds & Kamphaus, 2004
), the Conners Rating Scales (e.g., Conners, Sitarenios, Parker, & Epstein, 1998
) and the Early Childhood Inventory (ECI), Child Symptom Inventory (CSI), and Adolescent Symptom Inventory (ASI) developed by Gadow and colleagues (e.g., Gadow & Sprafkin, 1997a
; Gadow & Sprafkin, 1997b
; Gadow & Sprafkin, 1998
). Each of these measures can be completed quickly by parents or teachers to screen efficiently for a broad range of psychopathology, and all are used widely in both research studies and clinical practice. Scores from these measures do not replace diagnostic interviews, and are not intended to provide clinical diagnoses or to guide treatment planning in isolation. Instead, these norm-referenced rating scales provide reliable and valid indicators of areas in which an individual appears to be experiencing significant difficulty in comparison to others the same age, and these areas can then be targeted directly for more intensive evaluation.
In contrast to these well-validated screening measures for psychopathology, to our knowledge there are no scales designed to screen for specific learning disorders and related developmental difficulties. In this manuscript we describe the development of the Colorado Learning Difficulties Questionnaire (CLDQ), a parent-report rating scale that may provide a useful screening instrument for use in clinical settings and research studies. The CLDQ was designed to assess specific dimensions of functioning that are most often impaired in children with learning difficulties, including reading, math, social cognition, spatial functioning, and memory. Data from four large samples (total N =8,004) were used to evaluate the internal structure and convergent and discriminant evidence for the CLDQ scales. Specific goals were as follows:
- To assess the number of dimensions of learning difficulties assessed by the CLDQ, initial exploratory factor analyses (EFA) were completed in each sample, and a subsequent multigroup confirmatory factor analysis was used to test whether the factor structure could be equated across the four samples. We hypothesized that these analyses would identify separable dimensions of reading, math, spatial functioning, social cognition, and memory.
- The inter-rater reliability of each CLDQ scale was evaluated by examining correlations between maternal and paternal ratings, and estimates of test-retest reliability were obtained from maternal ratings completed approximately one year apart.
- The four datasets included a range of external measures of each of the constructs assessed by the CLDQ. Convergent and discriminant evidence for the CLDQ scales was evaluated by testing whether correlations were significantly higher between each scale and external measures of the same construct than measures of other constructs.
- CLDQ scores of groups with RD, MD, NVLD, and other developmental disorders were compared to test whether predicted associations were observed between each CLDQ scale and specific disorders. We expected that individuals with RD would exhibit higher elevations on a CLDQ Reading scale than any other scale that emerged in factor analyses of the CLDQ, whereas individuals with MD would exhibit the most pronounced elevations on a Math scale. Groups with NVLD were expected to score highest on on a CLDQ scale measuring spatial difficulties, and groups with NVLD or a pervasive developmental disorder (PDD) were expected to exhibit the most pronounced impairment on a CLDQ scale measuring social cognition.