| Paper Authors: | Elizabeth Gregory, Ivan Torres, Ruiyang Ge, Daniel Blumberger, Jonathan Downar, Zafiris Daskalakis, Raymond Lam, Fidel Vila-Rodriguez |
| Post Author(s): | Alice Erchov, Sarah Kessler, Fidel Vila-Rodriguez |
| Download the research article: | Gregory et al. – 2020 – Predictors of cognitive impairment in treatment-resistant depression |
Introduction
Depression is well-known to negatively impact mood, but relatively few studies have looked at how this disorder may impact cognition, or thinking ability. This is important because better cognitive ability is linked to better functioning in daily life (e.g., work or home responsibilities). This information could inform how we help people with depression. We do not know whether everyone with depression has difficulties with their cognition. We also do not know whether these difficulties span across all cognitive domains, or are specific to just a few (e.g., memory, learning). This study looked to answer these questions and identify what may predict worse cognitive impairment in those with treatment-resistant depression.
Methods
This study compared 60 people with treatment-resistant depression to 43 people without depression who were similar in age, sex, and IQ (before depression). The different aspects of cognition that were measured included:
- Verbal memory: the ability to remember and repeat as many words as possible from a list that was read out loud
- Inhibition: the ability to prevent thoughts or behaviours that work against task instructions
- Attentional shifting: to change the way you think or act within a task
- Verbal fluency: to think of as many words as possible in a short time, given a prompt
- Working memory: the ability to hold thoughts/words in memory while reordering them
Results
- Overall, those with treatment-resistant depression showed worse performance in tasks looking at attentional shifting, inhibition, and verbal memory
- Overall, there were no differences between those with treatment-resistant depression and those without on measures of verbal fluency and working memory
- A little over half of people with depression fit into a “cognitively impaired” group, which showed greater impairment in all measures when compared to the other half who were considered “cognitively unimpaired”. This difference was large for every domain except attentional shifting
- People were more likely to be “cognitively impaired” if they were using benzodiazepine medication, had lower IQ prior to illness, and were older
- Importantly, benzodiazepine was an important link between poor cognition and worsened daily function
Conclusion
This study found that individuals with depression can be roughly sorted into two groups based on cognitive function: an impaired group and an unimpaired group. Because we were able to find certain risk factors for cognitive impairment, it could inform the way we treat depression in the future (e.g., avoiding benzodiazepine medication, when possible).