How do social observations influence the efficacy of antidepressants?

People suffering from depression often have a long history of treatment attempts, with many having consulted a large number of doctors and having tried various different therapeutic treatment approaches. Over the course of these treatment attempts, they gather positive but also negative experiences, which in turn influence the efficacy of new treatment attempts, for instance with antidepressants. At the same time, patients meet other people with similar problems and swap stories about their experiences. This can likewise change individual expectations about the next treatment – which is how placebo and nocebo effects also influence the effectiveness of treatment.

Effects of antidepressant treatments on the neurobiological level

In Project A09, we are examining the mechanisms underlying these processes using an animal model. During the first funding period, our researchers developed a novel experimental design that allowed us to induce a depressive mood in rats, enabling us to study placebo and nocebo effects of antidepressant treatment on the neurobiological level. This provided us with insights into the biological processes involved, which would not have been possible in experiments with humans.

What role do social signals play in placebo and nocebo effects?

In the second funding period, we are substantially extending our experimental design to enable us to also examine the influence of social observations. For the first time, we are also using ultrasound vocalization as a social signal. This form of communication in rats cannot be perceived by humans. In particular, we will look in more detail at the influence of two brain regions, the nucleus accumbens and the amygdala, in the emergence of placebo and nocebo effects in depression.

How do social signals of rats and interactions between the animals influence antidepressant treatment? And what role do the amygdala and nucleus accumbens play in this regard? Finding answers to these questions will also provide valuable insights for humans, and in the long term, we hope to be able to improve the complex and often lengthy treatment of depression.