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Objective: To critically review contemporary theoretical models, diagnostic approaches, clinical features, and assessment findings in Functional Cognitive Disorder (FCD), and make recommendations for neuropsychological evaluation of this condition. Method: Narrative review. Results: FCD is common in neuropsychological practice. It is characterized by cognitive symptoms that are not better explained by another medical or psychiatric disorder. The cognitive symptoms are associated with distress and/or limitations in daily functioning, but are potentially reversible with appropriate identification and treatment. Historically, a variety of diagnostic frameworks have attempted to capture this condition. A contemporary conceptualization of FCD positions it as a subtype of Functional Neurological Disorder, with shared and unique etiological factors. Patients with FCD tend to perform normally on neuropsychological testing or demonstrate relatively weak memory acquisition (e.g. list learning trials) in comparison to strong attention and delayed recall performance. Careful history-taking and behavioral observations are essential to support the diagnosis of FCD. Areas of ongoing controversy include operationalizing "internal inconsistencies" and the role of performance validity testing. Evidence for targeted interventions remains scarce. Conclusions: Neuropsychologists familiar with FCD can uniquely contribute to the care of patients with this condition by improving diagnostic clarity, richening case formulation, communicating effectively with referrers, and leading clinical management. Further research is needed to refine diagnosis, prognosis, and treatment.

Objective: The current study examined the effect of depression on cognitive test performance in a sample of adults seeking treatment for a mild traumatic brain injury (MTBI). We hypothesized that patients with greater depressive symptoms would perform worse on tasks of fluid cognition compared to those without depression, after controlling for potential confounds., Method: Patients (N = 76) completed a brief cognitive test battery (NIH Toolbox Cognition Battery; NIHTB-CB) and a depression screening questionnaire (PHQ-9) at 11.7-weeks post injury (SD = 6.3 range 2-26). Cognitive scores were adjusted for age, education, gender, and race/ethnicity. Depressive symptoms were examined continuously and dichotomized as: (1) total PHQ-9 score of ≥ 10, the optimal cut-off for Major Depressive Disorder caseness from prior research, and (2) five or more symptoms of depression, including either depressed mood or anhedonia (i.e. DSM-5-based definition)., Results: Twenty-seven patients (35.5%) met DSM-5-based criteria for depression and 42 (55.3%) met criteria based on PHQ-9 > 10. Depression symptom severity correlated with lower fluid cognition composite scores [r = -.22, p = .05] and contributed to the prediction of fluid cognition performance in a model that controlled for time since injury and crystallized cognitive abilities [F(3, 72) = 7.49, p < .001; R 2  = 20.6%]. Examining specific NIHTB-CB fluid subtests, the largest group differences were seen on processing speed (d = .40-.49), cognitive flexibility (d = .32-.36), and episodic memory (d = .20-.34). Depression severity was strongly associated with overall post-concussion symptom burden (r = .77, p < .001)., Conclusion: Depression is a common comorbidity and an important factor to consider when interpreting neurocognitive test performance in adults with concussion in a clinical setting.

Objective: Youth with attention deficit hyperactivity disorder (ADHD) perform more poorly on preseason cognitive testing and report more baseline concussion-like symptoms but prior studies have not examined the influence of medication use on test performance or symptom reporting. This study investigated whether medication use is relevant when interpreting baseline ImPACT® results from student athletes with ADHD., Method: Participants were 39,247 adolescent athletes, ages 13-18 (mean age = 15.5 years, SD = 1.3), who completed baseline cognitive testing with ImPACT®. The sample included slightly more boys (54.4%) than girls. Differences in ImPACT® composite scores and concussion-like symptom reporting (between ADHD/No medication, ADHD/Medication, No ADHD/Medication, and Control groups) were examined with ANOVAs, conducted separately by gender., Results: In this large, state-wide data-set, youth with ADHD had greater rates of invalid ImPACT results compared to control subjects (ADHD/No Medication: girls = 10.9%, boys = 10%; ADHD/Medication: girls = 8.1%, boys = 9.1%; Controls: girls = 5.2%, boys = 6.7%). Groups differed across all ImPACT® composites (invalid profiles were removed), in the following order (from worse to better performance): ADHD/No Medication, ADHD/Medication, and Control participants. Pairwise effect sizes indicated that the largest differences were on the Visual Motor Speed composite, with the ADHD/No medication group performing worse than the ADHD/Medication group and the Controls. The ADHD/Medication group did not differ meaningfully from Controls on any composite, for either sex (d = 0 to .19). The ADHD groups did not differ on total symptom scores but both ADHD groups endorsed significantly more symptoms compared to Controls., Conclusions: Contrary to our hypothesis, we found medication use had only a subtle effect on cognitive performance and no significant effect on concussion-like symptom reporting. Student athletes reporting medication use for ADHD performed comparably to student athletes with no ADHD on baseline testing.

Embedded symptom validity measures facilitate the detection of below-capacity performance in neuropsychological assessment. A number of such indicators have been proposed for the Controlled Oral Word Association Test (COWAT), a widely used test of word generation. However, several of these embedded indicators have not been cross-validated and it is currently unclear which represent the optimal combination of predictors. This study used Bayesian Model Averaging (BMA) to determine the set of predictors that best differentiate between patients presenting with (n = 46) and without (n = 55) malingered neurocognitive dysfunction (MND). Mild traumatic brain injury was the most common diagnosis in the MND group (96%). BMA selected the COWAT total score and a measure of change in output over time. A logistic regression model combining these variables yielded good discriminability, with an AUC of. 774, (95% confidence interval = .679 to. 869), 78% of cases were classified correctly, with 67% sensitivity and 88% specificity. Two alternative models performed similarly, but the variables involved required slightly longer administration and/or calculation time, making them somewhat less desirable. These results support the use of a weighted combination of embedded symptom validity measures in the COWAT.

The present study investigated whether speeded word generation performance patterns seen in healthy subjects are also produced in genuine and feigned traumatic brain injury (TBI). An expanded version of the Controlled Oral Word Association Test was administered to healthy controls, TBI patients, simulated malingerers, and probable clinical malingerers. Four performance patterns were operationalized. Three of these patterns were replicated in the healthy control sample and found to be unaltered by genuine TBI. They were then combined into a logistic regression model that discriminated well between examinees who put forth adequate effort and those who evidenced response bias.

The present study aimed to develop an internal validity indicator for a brief general purpose screening battery, the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Two subtests of the RBANS were predicted to be relatively resilient to cognitive dysfunction on the basis of previous research. An Effort Index (EI) was created by combining them via a scaling system. The frequency of EI scores was first examined in a heterogenous clinical sample. A subsequent validation study showed good discriminability. In conclusion, the EI appears to be useful for detecting insufficient effort on a screening battery.