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Intelligence tests predict academic achievement in typically developed children, however if this is the case also in children with attention-deficit/hyperactivity disorder (ADHD) and/or autism spectrum disorder (ASD) is not clear. This systematic review and meta-analysis examined if Wechsler intelligence scales predict academic achievement and/or grades in children, ages 6-16 years, with ADHD and/or ASD. We searched the databases PubMed, PsycINFO and Education Research Complete for studies published between 2000 and 2023. We used the Newcastle-Ottawa Scale to assess risk of bias. Narrative synthesis and meta-analysis were performed. Twelve studies (ADHD n = 1,834, ASD n = 176) were included in the review, and six samples (ADHD n = 1,112) of those were included in the meta-analyses. The results of the meta-analyses showed moderate overall weighted correlations between IQ and word reading, written language, and mathematics respectively. Similarly, the overall weighted correlations between processing speed and the aforementioned domains of academic achievement were moderate. Meta-analysis with additional Wechsler scales composite scores could not be conducted. In the narrative synthesis, Full Scale IQ was associated with academic achievement in both ADHD and ASD, and grades in ADHD. The limited number of ASD participants and the heterogeneity of the samples need to be considered when interpreting results. Generally, the results indicate that Wechsler scales are valuable in predicting academic achievement in children with ADHD or ASD. Motivation and other factors related with academic achievement need to be further explored in these groups.

The Working Memory Index (WMI) in the Wechsler Intelligence Scale for Children (WISC) has been suggested to be associated with ADHD symptoms. The relationship between WMI and ADHD symptoms in the general population is not clear. The study aimed to examine the association between working memory (WM) and behavioral regulation (BR), and hyperactivity/inattention (HI) in a general population sample of 7-8-year-olds, and whether general intellectual functioning is associated with BR and HI. The study also examined if those with low WMI also fulfill elevated ADHD criteria. The study group (N = 865) was assessed with the WISC (Fourth edition), the Behavior Rating Inventory of Executive Function, the Strengths and Difficulties Questionnaire, and the Five to Fifteen Questionnaire, and divided into three groups based on WM function, and in relation to BR and/or HI problems. The associations between WM and BR, and WM and HI, including intellectual functioning as covariate, were examined. WM deficits were found in 22%, but the majority of those had no BR or HI problems. Four percent in the study group had WM deficits combined with BR and/or HI problems, and in about one third of those inattentive ADHD criteria were fulfilled. WM and prosocial behavior were associated with BR and HI. WM deficits measured with WISC WMI in 7-8-year-olds do not always signal BR and/or HI problems.

Aim We examined the association between the number of words used at age 2.5 years and deficits in intellectual functioning at age 7 years, in 549 children, and whether such association is confirmed by parental concern about the child's development. Methods Parental reports of how many words their children used at age 2.5 years were analysed for the association to intellectual functioning (assessed with Wechsler Intelligence Scale for Children - Fourth Edition,WISC-IV) at age 7 years using linear regression, adjusting for sex, maternal education level, parental IQ and smoking during pregnancy. Parental concern at age 7 years was examined with the Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations-Questionnaire (ESSENCE-Q). Results Adjusted linear regression showed that use of 50 words or fewer at age 2.5 years, relative to use of more than 50 words, was associated with lower scores of Full-scale IQ (B = 7.27, p = 0.001), verbal comprehension (B = 8.53, p < 0.001), working memory (B = 9.04, p < 0.001) and perceptual reasoning (B = 4.21, p = 0.045), in the WISC-IV, at age 7 years. Parental concern was more common in the group that used 50 words or fewer (Mann-Whitney U test, p = 0.011). Conclusion This easily accessible measure of number of words seems to be a valuable marker for intellectual functioning later in life.