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 (ADM) 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 neuropsy-chological 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.