Severity and Correlates of Mental Fog in People with Traumatic Brain Injury

ObjectiveAlongside objective performance declines, self-reported cognitive symptoms after traumatic brain injury (TBI) abound. Mental fog is one symptom that has been underexplored. The current project investigated mental fog across two studies of individuals with mild traumatic brain injury and moderate-to-severe traumatic brain injury to close our knowledge gap about differences in severity. We then explored the cognitive and affective correlates of mental fog within these groups. MethodsUsing between-groups designs, the first study recruited individuals with acute mild TBI (n = 15) along with a healthy control group (n = 16). Simultaneously, a second study recruited persons with post-acute moderate-to-severe TBI, a stage when self-reports are most reliable (n = 15). Measures across the studies were harmonized and involved measuring mental fog (Mental Clutter Scale), objective cognition (Cogstate(R) and UFOV(R)), and depressive symptoms. In addition to descriptive group difference analyses, nonparametric correlations determined associations between mental fog, objective cognition, and depressive symptoms. ResultsResults revealed higher self-reported mental fog in acute mild TBI compared to healthy controls. And though exploratory, post-acute moderate-to-severe TBI also appears characterized by greater mental fog. Correlations showed that mental fog in mild TBI corresponded to greater depressive symptoms (r = .66) but was unrelated to objective cognition. By contrast, mental fog in moderate-to-severe TBI corresponded to poorer working memory (r = .68) and slowed processing speed (r = -.55) but was unrelated to depressive symptoms. ConclusionAs a common symptom in TBI, mental fog distinguishes individuals with acute mild TBI from uninjured peers. Mental fog also appears to reflect challenges in recovery, including depressive symptoms and objective cognitive problems. Screening for mental fog, in addition to other cognitive symptoms, might be worthwhile in these populations.