Abstract/Summary

Depression often emerges in adolescence; however, current psychological therapies for adolescents with depression are modest at best. A better understanding of mechanisms that cause and maintain depression could lead to significant improvements in the effectiveness of treatment. A core cognitive process in depression is Overgeneral Memory (OGM). OGM appears to play a role in maintaining depression, increasing the risk of relapse, and may also be implicated in aetiology. The CaR-FA-X model proposes three mechanisms that may cause OGM (rumination, functional avoidance and reduced executive control). There is some empirical support for each component, but no study has explored all three mechanisms in adolescent depression. The aim of this thesis was to assess OGM and the CaR-FA-X mechanisms in adolescent depression and to investigate potential ways to enhance working memory. Paper 1 investigated OGM and the components of the CaR-FA-X model in adolescents with elevated depression symptoms and compared findings to youth with low depression symptoms. Adolescents with elevated depression retrieved fewer specific memories, ruminated more, and had poorer working memory and verbal fluency. Post hoc analysis also revealed that OGM was associated with higher levels of rumination and poorer working memory and verbal fluency. Paper 2 recruited adolescents with a diagnosis of depression and those with an anxiety disorder and compared them to a matched non-clinical control group. OGM and working memory deficits were specific to the depression group. Anxious and depressed participants had impaired inhibition and rumination compared to the non-clinical controls. OGM was associated with increased rumination and reduced working memory and inhibition performance. These findings suggest that working memory is a potential target for prevention and treatment interventions for depression. Paper 3 systematically reviewed meta-analyses of the effectiveness of working memory training. This demonstrated that working memory training has limited effects and effects do not generalise to ‘real life’ tasks. There is emerging evidence that dietary flavonoids may enhance executive control and mood. Therefore paper 4 reports a double-blind randomised controlled trial comparing effects of a chronic flavonoid supplementation and a placebo on mood and executive functioning in young people. Following the flavonoid intervention, depression symptoms, but not cognition, improved. Taken together, this body of work provides valuable insight into depression-specific working memory deficits in adolescents, which has important implications for therapeutic and school environments.