Srinivasan, Ramya; (2025) Childhood Irritability, Reward Processing and Adolescent Depression. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

BACKGROUND: Depression increases during adolescence, but we do not understand why. Prior irritability is associated with future depression. Both have been linked to alterations in reward processing. Despite this potential connection, reward processing has been relatively understudied as a possible factor underlying the two. AIMS: In this thesis, I aim to investigate the relationships between irritability, adolescent depression and a specific aspect of reward processing which I refer to as risk-taking. METHODS: I conducted a narrative review of the literature surrounding childhood irritability, its relationship with depression, and reward processing in relation to both irritability and depression. Given the broad nature of reward processing, I focussed on a specific aspect: risk-taking, measured by the Cambridge Gambling Task (CGT). In a cohort at familial risk of depression (Early Prediction of Adolescent Depression study, EPAD), I investigated whether prior irritability is associated with reduced risk-taking on the CGT similar to that possibly observed in depression. Then, using a nationally representative UK based cohort study (Millenium Cohort Study, MCS), I examined the association between changes in childhood irritability and adolescent depressive symptoms. Finally, using trial-by-trial CGT data, I investigated the associations between changes in childhood irritability and risk-taking in MCS. RESULTS: In EPAD, those with higher irritability appear to bet relatively more at less favourable ratios. In MCS, irritability which does not decrease as expected during childhood is associated with adolescent depressive symptoms and, with higher risk-taking per trial, particularly on trials following a win. CONCLUSIONS: Prior irritability is associated with subsequent depression. Irritability may be associated with altered risk-taking on the CGT, albeit not in the manner which has previously been associated with depressive symptoms. Future research requires longitudinal cohorts with measures of irritability, depression, and appropriate cognitive tasks to identify changes in symptoms in relation to development.

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