2 May 2019
Using economic models to understand decision-making in mental health disorders
We caught up with Professor Marco Bonetti to discover whether economic models could be applied in mental health research to better explain how OCD patients make decisions under risk.
What is the rationale behind your research?
Classical models of decision-making under risk, used in psychiatry, do not adequately explain real patterns in patients’ behaviour. In this study we investigated whether applying economic decision-making models to mental health research could address this need.
Thanks to the unique collaboration between Bocconi University and San Raffaele Hospital, we were able to study decision-making patterns in OCD patients specifically.
OCD patients shown a general deficit in decision-making when compared to healthy subjects, especially under ambiguity (when probabilities are not known). However, the direction for impairment in decision-making under risk (when probabilities are known) is still unclear. Some authors claim a deficit is present (especially in choosing the most likely outcome) while others find no differences.
Which methods did you use?
We examined Cambridge Gambling Task (CGT) data from 81 OCD patients and 124 healthy controls. We tested two theories which can describe how decisions makers rank lotteries (distributions of probability over payoffs): Expected Value and a new formulation of Disappointment Theory. According to the first, lotteries are ranked based on their expected value. According to the second, when evaluating a lottery people incorporate some disappointment (elation) feelings that might arise when comparing an outcome with all possible better (worse) outcomes in the same lottery.
What are your key findings?
We found that OCD subjects had a higher propensity towards risk neutrality (an individual is considered risk neutral if they are indifferent between getting 50 for sure or 100 with probability 0.5, for example). Conversely, healthy controls are more consistent with the predictions of Disappointment Theory.
It is widely accepted in behavioural economics that individuals show decision patterns influenced by emotions like regret (the feeling arising from comparing consequences of different actions under the same realization, like carrying or not an umbrella when it rains) or disappointment (the feeling arising from comparing consequences of the same action under different realizations, like carrying an umbrella when it rains or not). OCD subjects seem to be less prone than healthy individuals to these biases. On the other hand, that might be a signal of some form of risk loving behaviour (there is some evidence which links OCD to pathological gambling).
What is the potential impact of your research?
We would like to highlight the fact that “In the United States, about 1 in 40 adults and 1 in 100 children have OCD. And according to the World Health Organization, OCD is one of the top 20 causes of illness-related disability, worldwide, for individuals between 15 and 44 years of age." It is a relatively common condition that can seriously impact patients’ lives. In particular, when it comes to risk preferences, it can impact financial decisions and lead to severe consequences.
Furthermore, from a more research-oriented point of view, understanding how decisions by OCD patients differ from decisions made by healthy individuals can help researchers interested in decision-making isolate the neurological underpinnings of preferences regarding risk.
Why did you choose CANTAB?
CANTAB is a very good choice. It is a flexible tool and it is extremely easy to use both for experimenters and, most importantly, for patients. In the case of hospitalized patients, user friendly devices are very important given the situation of distress, since they add little psychological burden to an already stressful situation.
The team of Cambridge Cognition was extremely helpful and supportive. We asked for support in the disaggregation of the data and they were extremely responsive. Indeed, we did not simply analyse the routine output produced by CANTAB, but rather we had to disaggregate all individual choices to perform our analyses.
About the authors
Our work is the result of a close collaboration between Bocconi University and San Raffaele University Hospital in Italy. Bocconi University is an institution focused on social sciences, which contributed to shape Italian economy and society since its foundation. San Raffaele University Hospital is one of the leading medical institutions in the country.
Some of the authors have a background in Economics and are interested in decision-making from a theoretical and experimental point of view. Some of the authors have a background in medical statistics and are familiar with clinical data. Finally, the remaining authors of the article have a background in psychology and neurosciences, and they are interested in decision-making from a psychological and clinical point of view.
Interested in discovering the latest research papers in your field?
 See Delquié and Cillo (2006)
Prof. Marco Bonetti, Professor of Statistics, Bocconi University