Previous research has explored the performance of working memory in children with ADHD and individual co-occurring disorders, finding that internalizing disorders such as depression and anxiety, both independently negatively impact working memory performance (Saarinen, Fontell, Vuontela, Carlson, & Aronen, 2015; Kofler, Rapport, Bolden, Sarver, Raiker, & Alderson, 2011; Skogan, Zeiner, Egeland, Rohrer-Baumgartner, Urnes, Reichborn-Kjennerud & Aase, 2013). However, there is limited research on the impact of co-occurring depression and anxiety on working memory, which are common in children with ADHD. When depression is present, parts of the prefrontal cortex regions are hypoactive and therefore lead to impairment in executive functioning abilities (Snyder, 2013). In regard to anxiety, previous literature (Moran, 2016) has found that anxious arousal competes with processes located in the prefrontal cortex leaving limited neural resources for executive functioning skills (Moran, 2016). The current study will evaluate the influences of depression and anxiety on working memory in children with ADHD.

Participants were from an archived data set, which included 849 individual children ages 7-15 years old and their biological parents, recruited between 2009 and 2015. The 849 children included 76 sibling pairs. Families were part of an ongoing longitudinal study. The children completed a computerized version of a spatial working memory task identical to the spatial span task from CANTAB (De Luca et al., 2003). In regard to verbal working memory, children completed Digit Span from the WISC-IV, including both forward and backward conditions. Depression was measured by the Children’s Depression Inventory, 2nd edition (Kovac, 2004) and anxiety was measured by the Multidimensional Anxiety Scale for Children, 2nd edition (MASC-2) (March, 2012). ADHD was measured by having the parents and teachers complete two questionnaires: the ADHD rating scale (ADHD-RS; DuPaul et al. 1998), the Connor’s Rating Scale, 3rd edition (CRS-R, Connors 2003), and an in person semi-structured diagnostic interview (Kiddie Schedule for Affective Disorders and Schizophrenia -KSADS, Kaufman et al. 1997). A best estimate DSM-IV ADHD (American Psychiatric Association [APA], 1994) diagnosis was established by a multidisciplinary diagnostic team (ADHD diagnosis agreement kappa = .88). On cases where consensus was not achieved, they were excluded from the participant pool, and this became the clinical referred control group for the study.

The results indicated that children with ADHD and a co-occurring diagnosis of depression experience more difficulties with working memory abilities than those who do not have a co-occurring diagnosis of depression. Additionally, depression has a greater impact on verbal working memory in children with ADHD than anxiety does alone. This study also found that there were no significant gender differences between children with ADHD who identify as males and females on verbal or visual working memory tasks.

The findings of this study indicate the importance of addressing depressive symptoms in children with ADHD. With a holistic understanding of working memory deficits in children with ADHD as well as potential gender differences, caretakers and providers can integrate more effective intervention plans to help mitigate significant working memory deficits.