Browsing by Author "Vaija, Panu"

Depressive disorders and especially Major Depressive Disorder (MDD) have recently raised a lot of concerns. According to Bains & Abdijadid, (2022), in 2030 MDD will be the most common concern in terms of mental well-being and Kessler & Bromet (2013) pointed out that MDD “has one of the highest lifetime prevalence among psychiatric disorders”, and for this reason MDD results in a significant burden from an individual and societal perspective (Lépine & Briley, 2011). Anhedonia which is a core symptom of MDD (Gorwood 2008, Liang et al. 2022) can be defined as the “inability to enjoy experiences or activities that normally would be pleasurable” (APA Dictionary of Psychology, n.d.-c). Its effects on cognitive processes such as reward responsiveness has been the interest of various studies. Pizzagalli et al. (2008) demonstrated in their study that individuals suffering from MDD and experiencing anhedonic symptoms have a blunted reward responsiveness compared to some healthy subjects. This master thesis aimed to replicate Pizzagalli et al. (2008) study to reinvestigate anhedonia´s impact on reward responsiveness as well as anxiety´s role since individuals suffering from MDD also face anxiety or anxiety disorder (Xin et al. 2015).Two groups were formed, a clinical group (N=29) based on the DSM-IV criteria and a control group (N=20), and both groups were given the Face Game or the Probabilistic Reward Task (Pizzagalli et al. 2008) to measure reward responsiveness. Reward responsiveness was computed as “response bias” and the perceived difficulty of the task as “discriminability”. The results showed no significant difference in response bias scores between the depressed and healthy participants, and no significant correlations were found between depression scores, anhedonia scores, anxiety scores, and response bias scores. An effect of the experimental task’s blocks on response bias and discriminability scores was found, but no interaction effect (group * block) was found for the response bias and discriminability scores. Thus, we cannot argue in favor of the results obtained by Pizzagalli et al, (2008) that individuals suffering from MDD and especially experiencing anhedonic symptoms are more likely to have a blunted reward sensitivity compared to some healthy subjects. The statistically non-significant results were attributed to the small sample size, the complexity of the task and its design. Therefore, further investigations should focus on getting larger clinical and control groups and they also should redefine some aspects of the experimental task to make it more sensitive to any changes to reward responsiveness among individuals suffering from MDD and experiencing anhedonic symptoms.