Depression and anxiety are two common mood disorders that have been on the rise worldwide. Anxiety and depression can often occur together. It has been found that when anxiety is present alongside depression, the outcomes of treatment tend to be worse, suggesting that it may be a distinct and more severe subtype of depression.
The traditional way of classifying mental disorders using the Diagnostic and Statistical Manual of Mental Disorders (DSM) has been criticized because it doesn’t fully capture how these disorders actually work. In other words, the DSM diagnoses don’t always tell us which treatments will work for individuals, suggesting that there are different underlying causes for these disorders. To address this challenge, the Research Domain Criteria (RDoC) framework tries to understand psychiatric disorders based on how the brain circuits are affected.
Both depression and anxiety can affect the way people avoid certain situations or seek rewards. Avoidance can involve acting to avoid an unpleasant consequence OR inhibiting the desire to act to do so. For example, when trying to avoid an individual in your psychology course one might use an active avoidance strategy by enrolling in another course section. Conversely, one might use an inhibitory avoidance strategy by waiting until the person has left the class before getting up. However, we don’t yet understand whether specific avoidance behaviours characterize depressive symptoms, especially when anxiety is also present. Additionally, it’s not clear how the symptoms of depression and anxiety can predict whether someone actively seeks rewards or avoids them, especially when faced with uncertainty or conflicting motivations.
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In this research program we are using versions of experimental tasks requiring active and inhibitory avoidance and reward-seeking that are adapted from tasks used with rodents that allow us to measure conserved behaviours across species. Here we can administer computer tasks online to a large population of students and online workers, while also measuring a wide range of anxiety and depression symptoms. We can also use these tasks to examine patterns of behaviour in participants seeking treatment for major depression – with and without high levels of accompanying anxiety. In a recently published study we explored the degree to which scores on questionnaires measuring levels of anxiety and depression predicted avoidance or reward-seeking actions, and whether there were differences between men and women in how they do so. We are currently examining the relationship between anxiety and depression scores and the degree to which people can flexibly switch between avoidance and reward seeking behaviours, as well as biases in their tendency toward active or inhibitory behaviours when circumstances are ambiguous.
A related line of research using human brain imaging (functional magnetic resonance imaging, or fMRI) is examining the degree to which brain systems found to underlie active and inhibitory avoidance in rodents is reflected in patterns of human brain activation. Our lab has further innovated approaches to using fMRI to model the information instantiated by these brain systems. We plan to use these methods to determine whether these regions show distinct patterns of information for different types of depression and whether these might change with treatment. At the same time, the Floresco lab is building on our findings in humans by using drug manipulations in rodents to see what neurochemicals drive active/inhibitory behaviours that characterize depression subtypes. In turn, these findings may inform decisions about what drugs will best help individuals seeking treatment.
In the future we hope to additionally use pharmacological challenges to study the neuropharmacology of avoidance behaviours in the human brain. We will combine insights from human cognitive psychology and neuroscience and findings from animal experiments that have been adapted for use in humans. Our goal is to bridge the gap between research on the brain and mental disorders in humans and the valuable information gained from studying non-human animals.
