ABSTRACT
A quarter of children with Specific Learning Disorder (SLD) have a comorbid attention deficit hyperactivity disorder (ADHD), which impacts the testing of intelligence. ADHD is therefore treated before proceeding with the assessment of intelligence. It is expected that the treatment of ADHD will mitigate its effects on intelligence testing. Though this is frequently done in clinical practice, we could not find any study comparing IQ profiles of children having SLD with and without ADHD after treating ADHD to look for any changes between them. Therefore, we planned this study to compare the cognitive profiles of children having SLD with and without ADHD and describe any difference in their profiles. It was a retrospective cross-sectional study. We compared 695 children having SLD with treated ADHD to 721 children having SLD without ADHD on their WISC III profiles. We found that children having SLD with treated ADHD scored significantly lower on Digit Span and Coding. We suggest routine use of Cognitive Working Memory Training, peer tutoring, and task modifications in children having SLD with ADHD along with medicines and remedial education for better outcomes.
Keywords: ADHD, cognitive, IQ, SLD, WISC
Specific Learning Disorder (SLD) is an important cause of scholastic backwardness. Kuriyan and James reviewed 17 Indian studies (2000 to 2017) and found the mean prevalence of SLD as 10%.[1] Chacko et al. found a higher prevalence of 16.5% in school-going children in Kerala.[2]
Diagnosis of SLD requires that intellectual deficits should not explain learning difficulties.[3]
However, around 25% of children with SLD have a comorbid attention deficit hyperactivity disorder (ADHD), which impacts intelligence testing.[4] Studies have compared children having SLD and ADHD and found that children with ADHD are more impaired than SLD in cognitive inhibition, cognitive flexibility, verbal memory, working memory, and intellectual functioning.[5,6]
At our center, we screen children for ADHD before proceeding with IQ assessment. Further evaluation is done only after treating ADHD.
Though this is a frequent practice, we could not find any study which has compared IQ profiles of children having SLD with and without ADHD after treating ADHD.
Hence, we planned this study to compare WISC III profiles of children having SLD with and without ADHD (after symptomatic control of ADHD) and describe any differences in their cognitive profiles.
METHODS
A retrospective cross-sectional study was conducted at the Centre for Learning Disability, Department of Psychiatry at a tertiary care teaching hospital. Approval was obtained from the Institutional Ethics Committee.
Children who were issued certificates for SLD with or without comorbid ADHD and had detailed reports of WISC III assessment were included in the study. Diagnosis of SLD and ADHD was made by a multidisciplinary team including psychiatrists, pediatricians, psychologists, and special educators.
Children with deficits in all three domains of reading, writing, and arithmetic were included to provide homogeneity concerning learning deficits. Children having ADHD were included if they were better on treatment. Improvement was assessed clinically and on parents’ reports. Children were on treatment at the time of IQ assessment. Children having neurological issues, motor or sensory impairment, language barrier, or emotional issues were excluded so that these do not impact WISC III scores.
All children, who fulfilled the eligibility criteria from January 2013 to December 2017 (5 years) were included in the study.
Measures used
Wechsler Intelligence Scale for Children-third edition (WISC III):[7,8]
It assesses intelligence in children from 6 to 16 years of age. IQ is reported as Verbal IQ (VQ), Performance IQ (PQ), and Full-Scale IQ (FSIQ), which are standard scores obtained by comparing an individual’s score with those earned by a representative sample of age peers (Mean 100, SD 15). It has ten mandatory and three supplementary subtests. Subtests have a mean score of 10 with an SD of 3 points.
Verbal subtests include information, similarities, arithmetic, vocabulary, comprehension, and digit span (DS). DS is the supplementary subtest on the verbal scale. It may be substituted for another subtest if that subtest is spoiled.
Performance subtests include picture completion (PC), coding (CO), picture arrangement, block design, object assembly (OA), mazes, and symbol search. Mazes and Symbol Search are the two supplementary subtests on the performance scale. Mazes may be substituted for any subtest; however, symbol search may only be substituted for CO.
The average reliability for VQ is 0.95, PQ is 0.91 and FSIQ is 0.96. For individual subtests, reliability coefficients range from 0.69 to 0.87.
Data analysis
Data were analyzed using IBM SPSS version 20. Descriptive statistics were used to divide children into those having SLD with and without ADHD. Mean and Standard Deviation (SD) were computed for age and IQ scores. An independent t-test was used to compare the groups on age and IQ. The Chi-square test was used to determine the association between gender and the diagnosis. Statistical significance was considered at P < 0.05. 95% Confidence Intervals (CI) were also computed for the comparisons.
RESULTS
A. Description of the sample:
We screened files of 6000 children referred for assessment of scholastic backwardness and found that 3196 (53.3%) had SLD. Among those 1416 fulfilled the eligibility criteria for our study. There were 1012 males and 404 females. 721 children (50.9%) had SLD without ADHD (S-ADHD), and 695 children (49.1%) had SLD with ADHD treated (S+ADHDt).
The mean age of children having S-ADHD was 13.31 ± 1.82 years. The mean age of children having S+ADHDt was 12.75 ± 2.09 years. This difference was statistically significant. (t-statistic: 5.444, P value: <0.001, 95% CI of difference between means: 0.36-0.77).
Whereas 241 females (33.4%) and 480 males (66.6%) had S-ADHD, 163 females (23.5%) and 532 males (76.5%) had S+ADHDt, This difference was statistically significant. (Chi-square statistic: 17.260, P value: <0.001, Odds Ratio: 1.64,95% CI: 1.3,2.7). We found that males are 1.64 times as likely as females to have SLD with ADHD.
B. Comparison of WISC III cognitive profile:
We found no statistically significant difference between the two groups on any of the standard scores (VQ, PQ, and FSIQ) [Table 1].
Table 1.
Comparison of groups on WISC III composite scores
| Standard scores | SLD without ADHD (S-ADHD) Mean score (SD) | SLD with ADHD (S+ADHDt) Mean score (SD) | t-statistic | P | 95%CI of difference between means |
|---|---|---|---|---|---|
| VQ | 101.61 (16.15) | 100.90 (16.43) | 0.818 | 0.413 | -0.99 to 2.41 |
| PQ | 110.75 (14.39) | 109.90 (14.38) | 1.118 | 0.264 | -0.65 to 2.36 |
| FSIQ | 106.63 (15.45) | 105.47 (16.35) | 1.365 | 0.173 | -0.51 to 2.81 |
On comparing the groups on various subtests of VQ, we observed a statistically significant difference in Digit Span [Table 2].
Table 2.
Comparison of groups on various subtests of VQ
| Verbal subtest | SLD without ADHD (S-ADHD) Mean score (SD) | SLD with ADHD (S+ADHDt) Mean score (SD) | t-statistic | P | 95%CI of difference between means |
|---|---|---|---|---|---|
| Information | 7.64 (3.29) | 7.38 (3.47) | 1.415 | 0.157 | -0.10 to 0.61 |
| Comprehension | 11.39 (3.40) | 11.54 (3.32) | 0.870 | 0.385 | -0.51 to 0.20 |
| Arithmetic | 7.05 (2.92) | 6.92 (2.93) | 0.830 | 0.406 | -0.18 to 0.43 |
| Similarity | 11.97 (3.41) | 11.85 (3.69) | 0.639 | 0.523 | -0.25 to 0.49 |
| Vocabulary | 12.01 (3.54) | 12.23 (3.35) | 1.217 | 0.224 | -0.58 to 0.14 |
| Digit Span | 11.27 (3.37) | 10.87 (3.33) | 2.276 | 0.023 | 0.06 to 0.76 |
On comparing the groups on various subtests of PQ, we found a statistically significant difference in Coding and Picture Completion [Table 3].
Table 3.
Comparison of groups on various subtests of PQ
| Performance subtest | SLD without ADHD (S-ADHD) Mean score (SD) | SLD with ADHD (S+ADHDt) Mean score (SD) | t-statistic | P | 95%CI of difference between means |
|---|---|---|---|---|---|
| Picture completion | 11.71 (2.53) | 12.11 (2.61) | 2.904 | 0.004 | -0.66 to -0.13 |
| Picture arrangement | 11.89 (2.65) | 12.10 (2.40) | 1.575 | 0.115 | -0.48 to 0.05 |
| Block Design | 11.91 (3.55) | 11.99 (3.53) | 0.424 | 0.671 | -0.45 to 0.29 |
| Object Assembly | 12.65 (3.56) | 12.27 (3.42) | 2.033 | 0.052 | 0.01 to 0.74 |
| Coding | 10.82 (3.42) | 10.06 (3.31) | 4.256 | <0.001 | 0.41 to 1.11 |
| Mazes | 9.82 (3.18) | 9.61 (3.12) | 1.272 | 0.024 | -0.12 to 0.54 |
DISCUSSION
The mean age of children having S+ADHDt was lower than those having S-ADHD. This may be because children having SLD with ADHD showed more impairment in academics and behavior. They were noticed earlier by parents and/or teachers, and hence, referred for assessment at an earlier age as compared to children having S-ADHD. ADHD symptoms are an independent predictor of academic performance.[9] Children with ADHD symptoms are likely to encounter greater academic difficulties which may be identified earlier.
Males are more likely to have SLD with ADHD in comparison to females. Our findings support the existing literature that ADHD is more frequent in males as compared to females with an approximate ratio of 2:1.[3]
Children having S+ADHDt scored lower than those having S-ADHD on all three standard scores. Although this difference was not statistically significant, study results are more compatible with lower scores for children having S+ADHDt.[10,11]
On comparing scores on various subtests, we found that children having S+ADHDt scored significantly lower on Digit Span (DS) and Coding (CO). They also scored lower on Object Assembly (OA). However, they scored significantly higher on Picture Completion (PC).
DS is a measure of short-term verbal memory and attention. CO measures short-term nonverbal memory and processing speed.[7]
Children with ADHD have impairments in working memory, processing speed, and executive functions like planning, and organization. Also, children with ADHD & language-based SLD have weaker working memory as compared to children having only ADHD.[5]
Our findings of lower scores on DS and CO are consistent with the literature that children having ADHD with SLD perform poorer on tasks based on working memory. However, a key point to note here is that, in our study, children were on treatment for ADHD at the time of assessment. Still, they scored lower. It may be that initially, scores on DS and CO were extremely low, and even after treatment they improved but remained significantly low. On the other hand, it may be that these areas did not improve much with treatment and remained the same.
In either case, we propose that despite taking treatment, tasks based on DS and CO continue to remain affected in children having S+ADHDt. Hence, for better outcomes, they need special training in these areas. We suggest including Cognitive Working Memory Training (CWMT) as a regular remedial measure for children having SLD with ADHD.[12] Furthermore, academic interventions like peer tutoring and task modifications (reducing task length, dividing tasks into sub-parts, and giving explicit instructions) should be regularly implemented for these children for better outcomes.[13]
In contrast to the above, we found that children having S+ADHDt scored significantly higher on PC. PC evaluates visual perception, visual recognition of an object’s basic details, and organizing visual material. It is a measure of a child’s ability to recognize familiar items and to identify missing parts.[7] Though planning and organization are weak in ADHD, our findings of higher scores for children having S+ADHDt could be because scores on PC are one of the earliest to improve with treatment.
Moreover, we found that children having S+ADHDt scored lower on OA, though this difference just missed statistical significance. OA is a measure of perceptual organization. It is the ability to visualize parts of a concrete object and reassemble these parts into the whole.[7] Children with ADHD have deficits in executive functions like planning and organization which explains their lower scores in our study. Statistical non-significance may be explained by probable improvement in scores with treatment.
Limitations and future directions
Our study was retrospective in nature. Prospective studies comparing WISC profiles of the same group of ADHD children, before and after treatment, will give a better understanding of the impact of treatment on various subtest scores.
We did not gather data regarding the duration of ADHD symptoms, scores on ADHD rating scales, the dosage of drugs given, and duration of treatment. Also, as our study included children tested over five years, most children were assessed on WISC III.
Studies focussing on the severity of ADHD and the role of CWMT in the management of symptoms will lead to a better understanding of this aspect.
CONCLUSION
There was no statistically significant difference in VQ, PQ, and FSIQ between the two groups. However, there was a statistically significant difference between DS and CO.
Despite taking treatment, children having S+ADHDt continue to have deficits in DS and CO. We suggest regular use of CWMT, peer-tutoring, and task modifications in addition to medicines and remedial education for better outcomes.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
REFERENCES
- 1.Kuriyan NM, James J. Prevalence of learning disability in India: A need for mental health awareness programme. First National Conference on Mental Health Education, NIMHANS. Bangalore, India. 2018 [Google Scholar]
- 2.Chacko D, Vidhukumar K. The prevalence of specific learning disorder among school-going children in Ernakulam District, Kerala, India: Ernakulam Learning Disorder (ELD) study. Indian J Psychol Med. 2020;42:250–5. doi: 10.4103/IJPSYM.IJPSYM_199_19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Arlington, VA: American Psychiatric Association; 2013. [Google Scholar]
- 4.Jepsen JRM, Fagerlund B, Mortensen EL. Do attention deficits influence IQ assessment in children and adolescents with ADHD? J Atten Disord. 2009;12:551–62. doi: 10.1177/1087054708322996. [DOI] [PubMed] [Google Scholar]
- 5.Becker A, Daseking M, Kerner auch Koerner J. Cognitive profiles in the WISC-V of children with ADHD and specific learning disorders. Sustainability. 2021;13:9948. doi:10.3390/su13179948. [Google Scholar]
- 6.Faedda N, Romani M, Rossetti S, Vigliante M, Pezzuti L, Cardona F, et al. Intellectual functioning and executive functions in children and adolescents with attention deficit hyperactivity disorder (ADHD) and specific learning disorder (SLD) Scand J Psychol. 2019;60:440–6. doi: 10.1111/sjop.12562. [DOI] [PubMed] [Google Scholar]
- 7.Nicholson CL, Alcorn CL. Interpretation of the WISC-III and Its Subtests. 1993 [Google Scholar]
- 8.Wechsler D. Wechsler Intelligence Scale for Children. San Antonio, TX: The Psychological Corporation; 1991. WISC-III Manual. [Google Scholar]
- 9.Birchwood J, Daley D. Brief report: The impact of attention deficit hyperactivity disorder (ADHD) symptoms on academic performance in an adolescent community sample. J Adolesc. 2012;35:225–31. doi: 10.1016/j.adolescence.2010.08.011. [DOI] [PubMed] [Google Scholar]
- 10.Andrade C. The P value and statistical significance: Misunderstandings, explanations, challenges, and alternatives. Indian J Psychol Med. 2019;41:210–5. doi: 10.4103/IJPSYM.IJPSYM_193_19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Andrade C. A primer on confidence intervals in psychopharmacology. J Clin Psychiatry. 2015;76:15615. doi: 10.4088/JCP.14f09751. doi:10.4088/JCP.14f09751. [DOI] [PubMed] [Google Scholar]
- 12.Ackermann S, Halfon O, Fornari E, Urben S, Bader M. Cognitive working memory training (CWMT) in adolescents suffering from Attention-Deficit/Hyperactivity Disorder (ADHD): A controlled trial taking into account concomitant medication effects. Psychiatry Res. 2018;269:79–85. doi: 10.1016/j.psychres.2018.07.036. [DOI] [PubMed] [Google Scholar]
- 13.Daley D, Birchwood J. ADHD and academic performance: Why does ADHD impact on academic performance and what can be done to support ADHD children in the classroom? Child Care Health Dev. 2010;36:455–64. doi: 10.1111/j.1365-2214.2009.01046.x. [DOI] [PubMed] [Google Scholar]
