Patients with first-episode schizophrenia spectrum and comorbid depressive disorder showed better neurocognitive performance compared with patients without comorbidity, according to findings published in the Journal of Affective Disorders.
Researchers conducted a secondary analysis of data from a single blind, randomized controlled trial of vocational intervention for individuals age 15 to 25 years with first-episode schizophrenia spectrum (n=82). They sought to compare the neurocognitive profiles of people with first-episode schizophrenia spectrum with and without comorbid depressive disorder and to determine whether there is a relationship between severity of depressive symptoms and neurocognitive performance.
Of the 82 participants, 24 had comorbid full-threshold depressive disorder: 11 had major depressive disorder, 12 had depressive disorder not otherwise specified, and 1 had dysthymia.
The researchers used scores from 18 tests to examine 4 neurocognitive domains: verbal comprehension and working memory, verbal learning and memory, information processing speed, and visual organization and memory. The 18 neurocognitive raw test scores included the following: Wechsler Adult Intelligence Scale-Third Edition subtests (Digit Span, Letter-Number Sequencing, Similarities, Information and Picture Completion), the Trail Making Test A and B, Symbol Digit Modalities Test’s Letter Cancellation Task, Rey Auditory Verbal Learning Test, Rey-Osterrieth Complex Figure Test, Controlled Oral Word Association Test, and the Animal Fluency test.
After controlling for premorbid intelligence quotient and positive and negative psychotic symptoms, the researchers found that participants with comorbid depressive disorder showed significantly better information processing speed compared with those without depressive disorders. In addition, the severity of depressive symptoms was associated with better information processing speed.
There were no significant differences between those with and without comorbid depression in other neurocognitive domains.
Up to 80% of patients with first-episode schizophrenia spectrum have comorbid depressive disorder, which usually appears during the prodrome or first psychotic episode. However, medical professionals often overlook depressive disorder when researching and treating first-episode schizophrenia spectrum, instead focusing on treating psychotic symptoms.
“This is the first study to examine the influence of depressive disorder on neurocognitive performance in a sample of individuals free from the long-term effects of psychotic illness and other potentially confounding variables,” the researchers wrote. “Such novel findings are therefore more likely to accurately reflect the influence of depressive disorder during the post-psychotic phase on neurocognitive performance in this population and thus uniquely add to the current knowledge base.”
Herniman SE, Cotton SM, Killackey E, Hester R, Allott KA. Co-morbid depressive disorder is associated with better neurocognitive performance in first episode schizophrenia spectrum. J Affect Disord. 2018;229:498-505.