The negative impact of depression on cognitive functioning is well established, but a new study led by Keele University has found that depression is also associated with poorer perception. 

Dr Jim Grange from the School of Psychology—together with Dr Michelle Rydon-Grange from Midlands NHS Trust—has found preliminary evidence that higher levels of depression are associated with poorer perceptual encoding. Perceptual encoding refers to the processes that proceed—and thus enable—accurate identification of stimuli in our environment and are therefore essential for efficient cognitive functioning. 

In this research—published in the journal Psychological Medicine—Dr Grange conducted three separate large-scale experiments measuring the magnitude of participants’ depression symptoms and cognitive performance in an attention task.  

The attention task measured participants’ abilities to focus on task-relevant stimuli while ignoring irrelevant stimuli. Such visual selective attention is essential in everyday life; searching for a friend in a bar, for example, requires selective attention to ignore all the distracting information in your environment and select on relevant information to act on. Applying computational modelling to participant performance on the attention task allowed Dr Grange to isolate which component of visual selective attention was associated with depression symptoms. 

The findings—replicated across all three experiments—indicated that a component of the model that measures a participants’ perceptual encoding strength was consistently negatively associated with measures of depression symptoms: the more severe their depressive symptoms were, the worse their perceptual encoding was. 

Dr Grange said that these findings have implications for a new—broader—hypothesis that the cognitive deficits typically found in depressed populations could instead be problems that are made worse by perceptual deficits, adding that further research is now needed to investigate this. 

Dr Grange said: “Although this work is preliminary, it offers an intriguing explanation of poorer cognitive performance in those with depression. Some degree of caution is required, as our results so far are correlational in nature; we cannot yet be sure that depression causes perceptual deficits, just that the two factors are associated. Our work is now focussing on exploringn this “perceptual deficit” hypothesis in more detail, with the aim of understanding more deeply how perception and cognition interact in depression.”