The present study also had limitations. First, it is not clear how missing data affected the results, though the FIML method is most recommended (Arbuckle, 1996; Enders & Bandalos, 2001), and supplementary analyses showed negligible impact of stochastic imputation for five variables of NEPSY at F3. Second, although we included multiple time-points across early childhood, it is unclear whether these relations hold-up in older children, adolescents and adults. Therefore, future research needs to test whether these associations are evident later in life. Further, it needs to be noted that the NEPSY does not measure all facets of neuropsychological functioning and facets which are not measured in the present study could be associated with ADHD severity over time. Future studies may also include comparisons to understand whether the executive and non-executive domains of neuropsychological functioning are differentially related to ADHD severity.
