Have you been feeling anxious or depressed lately? It’s okay, 2016 has been tough on all of us.

Despite the discomfort that comes with negative emotions, they are a crucial part of our lives. However, when emotions get out of balance, they can lead to some pretty poor decision making.

In extreme cases it can get to the point where a person hardly leaves their house, acts highly aggressive, or becomes suicidal.

Anxiety and mood disorders (like major depression disorder) make up the most common mental disorders, particularly in European and Anglo-Saxon countries, where the lifetime morbid risk (i.e. the proportion of people who will eventually develop the disorder at some time in their life) can go as high as 29.9% for major depressive disorder, 18.4% for specific phobias and 13% for social phobia [1], meaning they affect the lives of millions of people. It is worth having a closer look at some of the underlying factors of depression and anxiety to improve treatments and to support and understand people better, before they develop a disorder. Here’s what we can learn about anxiety and depression from research on decision making.

Disclaimer: I use the term ‘anxiety’ in the wider, not necessarily clinical sense. Both, anxiety disorder and depression are very multifaceted and complex constructs. I do not claim to give an exhaustive introduction into either of these, but to give some insights into recent advances at the intersection of affective neuroscience and decision making.

Anxiety: “Am I in a stable or unstable environment?”

Imagine your partner starts a fight over some bagatelle. Are they just in a bad mood today, or has your relationship fundamentally changed for the worse? Anxious people seem to have a harder time answering this question, leading to possibly disadvantageous decision making.

In their 2015 study, Browning and colleagues investigated this phenomenon and showed that people with high levels of anxiety show poor decision making under uncertainty [2]. To be exact, anxious individuals are worse at dealing with second order uncertainty, which is caused by a changing environment, or uncertainty about already uncertain choices. In the study, participants had to avoid electroshocks by choosing one of two options. All participants were quick at learning which option to pick in the stable condition. However, in the unstable condition – that is when second order uncertainty comes into play – probabilities of shock delivery switched frequently between options and anxious people performed worse in avoiding the shocks. Anxious individuals also showed reduced pupil dilation in the unstable condition, compared to less anxious participants.

Pupil dilation has been argued to reflect activity of the locus coeruleus, a brain hub located in the brainstem, which is crucially involved in arousal and the emission of the neurotransmitter norepinephrine. Indeed, a recent study by Joshi, Li, Kalwani and Gold, revealed a direct link between neuronal firing rates in the locus coeruleus and pupil dilation related to alertness, not luminance [3]. So now we know, that anxious individuals have a harder time deciding if a surprising event signifies a fundamental change in the environment – at least for aversive outcomes. If this also applies to changes in reward-contingencies has yet to be investigated.

Here’s a neat and understandable summary of the study by Browning et al. Don’t take the information about the brain regions for granted, though. Be aware, that the detour to involved brain regions was not mentioned in the original study and is somewhat oversimplified. 

Depression: “Nothing will come of this anyway, so why waste my energy?”

Some of the main symptoms of clinical depression, according to the latest diagnostic and statistical manual of mental disorders (DSM-5) are loss of interest in activities, fatigue or loss of energy and psychomotor retardation (slowing of movements and speech). In short, depression can be characterized by a general lack of action, in addition to anhedonia (the inability to feel pleasure) which depressive patients often suffer from. Huys, Daw and Dayan (2015) argue, that the lack of action is caused by dysfunctional evaluation processes in the brain [4], or as I would put it ‘evaluation gone wrong’. They suggest that decision-making in depressed individuals is caused by a lower general utility rate. Simply put – when you are depressed, many actions seem not to be worth the effort, because the related costs exceed the expected rewards.

For example, going out and socializing takes a certain amount of energy and comes with risks. You might experience rejection and discomfort, but you might also have a good time and meet like-minded people. A person who suffers from depression is often going to choose not to go out, because for them, the effort of dressing up, leaving the house, talking to people, spending money on drinks and the possibility of facing rejection are overrunning the possible benefits of having fun and getting to know great people. This can go along with a number of factors, for example the reduced valuation of rewards. Many functional magnetic resonance imaging (fMRI) studies have found that people suffering from depression are indeed less responsive to rewards, which is reflected by reduced activity in reward-related brain areas, particularly the caudate nucleus [5]. Instead of reduced reward-signals, depression could also be characterized by a diminished motivation to approach or earn rewards [6].

Last, but not least

We know a lot about common symptoms of anxiety and depression and effective treatments have been developed over the last century, from psychotherapy to pharmacological treatments and even electrical stimulation (read about vagus nerve stimulation here). However, the mechanisms by which behavioral and cognitive (thought) processes are altered in anxiety and depression are not fully understood and even though antidepressants have helped a lot of people, it is not exactly clear how they work and why they sometimes fail to relieve patients of their symptoms. Hence, we need to find new ways of investigating the nature of mental disorders. Additionally, anxiety and depression often (if not mostly) occur together and are practically not very well distinguishable.

Developments in the field of decision-making offer new perspectives on understanding mental and neurological disorders on various levels and can help filling those knowledge gaps [7]. For example, as explained above, links between the locus-coeruleus-norepinephrine circuitry, pupil dilation and anxiety have been drawn by applying a model of decision-making.

Another exciting point is the possibility of assessing the efficacy of treatments using decision-making paradigms. Showing that a form of therapy improves a person’s decision-making skills can be a promising way to evaluate the effects of different treatments.

Finally, I want to emphasize that emotions can of course also be beneficial to decision-making processes. For example, a healthy amount of anxiety and caution will keep us from doing ‘something stupid’, possibly saving lives. Anger makes us take action against injustice, which is particularly relevant these days. Emotional contagion, be it joy or sadness, supports prosocial behavior and hence is ultimately advantageous for the whole group.

References

1. Kessler RC, Petukhova M, Sampson NA, Zaslavsky AM, Wittchen H-U. Twelve-month and lifetime prevalence and lifetime morbid risk of anxiety and mood disorders in the United States. Int J Methods Psychiatr Res. 2012;21: 169–184.
2. Browning M, Behrens TE, Jocham G, O’Reilly JX, Bishop SJ. Anxious individuals have difficulty learning the causal statistics of aversive environments. Nat Neurosci. 2015;18: 590–596.
3. Joshi S, Li Y, Kalwani RM, Gold JI. Relationships between Pupil Diameter and Neuronal Activity in the Locus Coeruleus, Colliculi, and Cingulate Cortex. Neuron. 2016;89: 221–234.
4. Huys QJM, Daw ND, Dayan P. Depression: a decision-theoretic analysis. Annu Rev Neurosci. 2015;38: 1–23.
5. Zhang W-N, Chang S-H, Guo L-Y, Zhang K-L, Wang J. The neural correlates of reward-related processing in major depressive disorder: a meta-analysis of functional magnetic resonance imaging studies. J Affect Disord. 2013;151: 531–539.
6. Whitton AE, Treadway MT, Pizzagalli DA. Reward processing dysfunction in major depression, bipolar disorder and schizophrenia. Curr Opin Psychiatry. 2015;28: 7–12.
7. Montague PR, Dolan RJ, Friston KJ, Dayan P. Computational psychiatry. Trends Cogn Sci. 2012;16: 72–80.