Computational modelling of effort-based decision-making in depression: The role of apathy and anhedonia in adolescent girls.

BACKGROUND: Adolescence is a period of heightened vulnerability to depression, particularly in females. Motivational deficits are a hallmark of depression, yet the cognitive mechanisms underlying impaired effort-based decision-making (EBDM) in female adolescents remain poorly understood. Computational psychiatry addresses this by fitting mathematical models to behavioural data and extracting latent parameters, offering a more mechanistic view. METHODS: This study used computational modelling to investigate the distinct effects of apathy and anhedonia on effort-based decision-making in adolescent girls with depression. Thirty-two adolescent girls with depression and 33 matched healthy controls performed a physical effort-based decision-making task. Participants accepted or rejected to exert different levels of physical effort to obtain different magnitudes of rewards or to avoid loss. Group differences were analysed utilizing a hierarchical Bayesian discounting model. RESULTS: The depression group exhibited a significantly reduced willingness to exert effort to obtain rewards, reflected by a lower accept rate and longer response time compared to the healthy control group. In line with this, the discounting model showed that the depression group had a higher effort sensitivity. Moreover, in the healthy control group, higher apathy levels were associated with a lower accept rate, whereas no such associations were observed for anhedonia; in the depression group, no significant associations were found for either apathy or anhedonia. CONCLUSIONS: This study identifies a computational signature of motivational deficits in female adolescent depression, characterized by oversensitivity to effort expenditure and modulated by apathy severity. By focusing on female adolescents, our findings highlight sex-specific mechanisms underpinning vulnerability to depression.