Erroneous Conclusions: The Impact of Failing to Identify Invalid Symptom Presentation When Conducting Adult Attention-Deficit/Hyperactivity Disorder (ADHD) Research

Invalid symptom report during assessment confounds the differential diagnosis process. This study examined differences in neuropsychological functioning between individuals diagnosed with attention-deficit/hyperactivity disorder (ADHD) and depression and/or anxiety disorders before and after participants meeting diagnostic criteria for malingered neurocognitive dysfunction were excluded. One hundred sixty-one adult patients undergoing ADHD assessment [M age 27.98 (8.35)] were evaluated and assigned to one of two groups based on medical records, a clinical interview, and self-report measures (depression/anxiety disorder n = 85; ADHD and depression/anxiety disorders n = 76). When all patients were considered, individuals with comorbid ADHD and depression/anxiety symptoms performed more poorly on 10 of 18 neuropsychological measures compared with those with only a depression/anxiety disorder (Cohen's d ranged from .32 to .72). In contrast, there was no evidence that the cumulative effect of ADHD and depression/anxiety resulted in diminished cognitive performance after excluding 54 patients with invalid symptom presentation. Additionally, the magnitude of association between self-report of ADHD symptoms and performance on neuropsychological test measures decreased dramatically. Thus, it is imperative that researchers administer performance and symptom validity measures to identify invalid symptom presentation when conducting large-scale studies. The failure to do so may result in inaccurate conclusions regarding the neurocognitive functioning of patients with ADHD and comorbid conditions. Public Significance Statement The present study suggests evaluation of performance and symptom validity is essential when conducting research studies. Prior to excluding individuals engaging in response distortion, individuals with comorbid ADHD and depression/anxiety symptoms exhibited greater neurocognitive impairment relative to patients experiencing only depression/anxiety symptoms. In contrast, after excluding individuals engaging in response distortion, there was no evidence of a cumulative effect of comorbid conditions on neurocognitive functioning.