Abstract
Lower performances in cognitive ability in individuals with Major Depressive Disorder (MDD) have been observed on multiple occasions. Understanding cognitive performance in MDD could provide a wider insight in the aetiology of MDD as a whole. Using a large, well characterised cohort (N = 7012), we tested for: differences in cognitive performance by MDD status and a gene (single SNP or polygenic score) by MDD interaction effect on cognitive performance. Linear regression was used to assess the association between cognitive performance and MDD status in a case-control, single-episode–recurrent MDD and control-recurrent MDD study design. Test scores on verbal declarative memory, executive functioning, vocabulary, and processing speed were examined. Cognitive performance measures showing a significant difference between groups were subsequently analysed for genetic associations. Those with recurrent MDD have lower processing speed versus controls and single-episode MDD (β = −2.44, p = 3.6 × 10−04; β = -2.86, p = 1.8 × 10−03, respectively). There were significantly higher vocabulary scores in MDD cases versus controls (β = 0.79, p = 2.0 × 10−06), and for recurrent MDD versus controls (β = 0.95, p = 5.8 × 10−05). Observed differences could not be linked to significant single-locus associations. Polygenic scores created from a processing speed meta-analysis GWAS explained 1% of variation in processing speed performance in the single-episode versus recurrent MDD study (p = 1.7 × 10−03) and 0.5% of variation in the control versus recurrent MDD study (p = 1.6 × 10−10). Individuals with recurrent MDD showed lower processing speed and executive function while showing higher vocabulary performance. Within MDD, persons with recurrent episodes show lower processing speed and executive function scores relative to individuals experiencing a single episode.
Highlights
Introduction Major DepressiveDisorder (MDD) is common mental disorder affecting at least 1 in 10 in the United Kingdom[1] and is a leading cause of disability worldwide
Snyder et al.[5] performed an extensive and the largest-to-date meta-analysis of cognitive performance in Major Depressive Disorder (MDD), focussing mainly on tasks that measure executive function (EF) with the exception of two non-EF tests measuring vocabulary and digit symbol substitution
No significant association was observed between MDD and cognitive test scores, except for digit symbol substitution in the singleepisode–recurrent comparison (β = −3.41, p = 5.8 × 10–04), with the recurrent MDD group recode fewer symbols to digit compared to single-episode MDD
Summary
Introduction Major DepressiveDisorder (MDD) is common mental disorder affecting at least 1 in 10 in the United Kingdom[1] and is a leading cause of disability worldwide. Snyder et al.[5] performed an extensive and the largest-to-date meta-analysis of cognitive performance in MDD, focussing mainly on tasks that measure executive function (EF) with the exception of two non-EF tests measuring vocabulary (language) and digit symbol substitution (processing speed, but is considered by some to be a component of EF) They observed that MDD patients showed a lower performance in phonemic verbal fluency and digit symbol measures. Lim et al.[6] conducted the largest meta-analysis study of LM to date (N logical memory immediate = 291; N logical memory delayed = 348) They observed that MDD patients performed significantly less well than controls on both LM immediate and delayed. The final domain examined, visuospatial processing (immediate and delayed visual memory), showed no differences between MDD patients and controls[6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
