Post by Stephanie Williams
What's the science?
The cognitive model of depression suggests that individuals with depression experience the world in a more negative way -- likely as a result of abnormal information processing and cognitive function. Although this model has been valuable in understanding depression, some researchers have argued that altered expectations, specifically, might underlie Major Depressive Disorder (MDD). Mismatches between predictions and expectation (also known as ‘prediction errors’) are used to update current belief models. Individuals with depression are known to generate predictions and process mismatches between predictions and expectations differently than people who are considered mentally healthy. This week in Biological Psychiatry, Kube and colleagues propose a new model that incorporates aspects of predictive processing to explain how learning from predictions can be affected in MDD.
How did they do it?
The authors review a collection of recent findings on cognitive processing in depression to propose a new model of depression focusing on expectations and predictive processing. They summarize key findings related to the neurobiology of prediction, behavioral studies and neurophysiological studies that support their framework for altered expectation and prediction error processing in MDD.
What did they find?
The authors propose that individuals with MDD predict negative experiences, discard positive information, and then find confirmation of those negative predictions. This process of discarding positive feedback is referred to as “cognitive immunization.” This framework suggests a biased learning process in individuals with depression, resulting in sustained negative predictions about their environment (i.e. a “negative feedback loop”). Interestingly, the authors point out that healthy individuals employ the same cognitive immunization strategy --- when faced with disconfirming negative information, healthy individuals discard the negative information and subsequently sustain positive expectations, which is related to optimism bias. Individuals with MDD rarely predict positive experiences, and consequently, miss the opportunity to perceive them. Specifically, the authors propose that individuals with MDD attend to negative experiences with greater precision, reducing the weight of positive experiences. The authors use their model to draw conclusions about learning rates in healthy and depressed individuals, which is dependent on the valence of the experience. They show that individuals with depression tend to maintain negative predictions longer than healthy people before updating them. The authors also suggest several brain regions involved in the maintenance of MDD, including the prefrontal cortex and the ventral striatal regions. The cognitive immunization strategy that individuals with MDD employ in the face of positive information may be supported by the suppression of prediction error processing in the ventral striatum by the prefrontal cortex.
What's the impact?
The authors proposed a novel model focused on expectation that helps advance our knowledge of distorted cognition in depression. Their proposed framework could inform treatment strategies, such as attempts to reduce individual use of cognitive immunization against positive information. The authors also propose future research involving prediction errors to better understand which types of prediction errors are critical in perpetuating depressive symptoms.
Kube et al. Distorted Cognitive Processes in Major Depression- A Predictive Processing Perspective. Biological Psychiatry (2019). Access the original scientific publication here.