Major depression (MDD) is known to affect numerous cognitive and behavioral domains. People with MDD often have pessimistic attitudes about future events and guilt over past events. They tend to isolate and withdraw, and choose to engage in activities that provide immediate reward over those that promise future enjoyment. This leads to impulsive and even risky behavior, like overeating and substance misuse.
Posttraumatic stress is an anxiety condition that has some similarities to MDD, but is unique in that risk/reward choices tend to be quite different. Understanding how people with MDD, PTSD, and MDD+PTSD value risks over rewards is an important area of clinical research and can provide insight into the behavioral and cognitive processes that take place in people with these mental health problems.
To get a closer look at the differences in decision making that occurs in these conditions, Jan B. Engelmann of the Department of Economics at the University of Zurich in Switzerland recently conducted risk/reward decision making experiments on 20 individuals. All had either MDD or MDD+PTSD. Engelmann compared their choices to those of 16 control (HC) participants.
The results showed that both MDD groups discounted long term rewards compared to controls. For gains, both MDD groups selected immediate versus long-term gains more than controls. However, when Engelmann looked at the subgroups of MDD participants, the findings revealed significant differences. The MDD only group demonstrated a preference for taking larger losses in the long term if it meant decreasing immediate losses. This was in contrast to the HC and MDD+PTSD groups, who chose smaller immediate losses over larger losses in the future.
Engelmann believes this difference in the MDD and MDD+PTSD group is due to anxiety. The PTSD group may be more willing to accept minimal losses today if it means avoiding larger losses later. This avoidant behavior is a symptom of anxiety and in the case of risk/reward may actually benefit individuals with respect to decision making.
For people with MDD+PTSD, although anxiety may decrease antidepressant efficacy, this negative consequence may be offset by the positive effect anxious symptoms appear to have on risk/reward processing. “Together,” added Engelmann, “These results inform future research investigating the underlying affective and cognitive processes, as well as related neural mechanisms, of the observed choice distortions in patients with MDD.”
Engelmann, J.B., Maciuba, B., Vaughan, C., Paulus, M.P., Dunlop, B.W. (2013). Posttraumatic stress disorder increases sensitivity to long term losses among patients with major depressive disorder. PLoS ONE 8(10): e78292. doi:10.1371/journal.pone.0078292
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