Apathy, Depression, and Emotional Lability in Patients with Amyotrophic Lateral Sclerosis
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The presence of cognitive and behavioral impairment in some patients with amyotrophic lateral sclerosis (ALS) is now well-known. However, the prevalence of behavioral impairment and the relationship between behavioral and cognitive impairment in ALS is not fully understood. This study is the first to examine systematically cognitive profiles associated with apathy, depression, and emotional lability (EL) in patients with ALS. Participants were 161 consecutive referrals to the Neurology service of the Houston Methodist Hospital MDA-ALS clinic. All patients met El Escorial World Federation of Neurology diagnostic criteria for probable or definite ALS. All participants underwent comprehensive neuropsychological evaluation, including measures of cognition, mood, and behavior. Multiple hierarchical regression analyses were used to predict performance on neuropsychological measures from apathy, depression, and emotional lability. Of the 161 patients, 24.8% were diagnosed with EL and 18.6% met criteria for DSM-IV-TR diagnosis of a mood disorder (including 9.9% with a Major Depressive Disorder (MDD) or Dysthymia and 8.7% with an adjustment disorder). Of the 117 with complete apathy data, 32.5% met criteria for clinically significant apathy. Approximately 22% of patients were experiencing two or more of these neuropsychiatric disorders. After controlling for disease severity, apathy accounted for significant variance in predicting performance on a measure of mental flexibility, over and above depression and emotional lability. Neither MDD nor EL significantly predicted performance on any neuropsychological measure. Results suggested that apathy, depression, and emotional lability co-occur, but are dissociable in ALS. After controlling for disease severity, only apathy was associated with executive functioning.