Fig. 4: Mental health score is associated with reward sensitivity.

a–f, A factor analysis was performed across all questionnaire sub-scales (PHQ, patient health questionnaire; AES, apathy evaluation scale; SHAPS, Snaith–Hamilton pleasure scale; DOPS, domain of pleasure scale) as well as life satisfaction and happiness, to reduce the dimension of the scores and ratings to a single factor score. The first factor explained about 70% of the variance in experiments 1 (a, N = 132 participants), 2 (b, N = 171 participants) and 3 (c, N = 180 participants) with similar loadings across studies. Negative loadings correspond to questionnaire scores that are negatively correlated with the factor; for example, as expected, a high depression score (PHQ) loads negatively on the mental health score. Positive loadings correspond to a positive correlation with mental health scores; for example, as expected, the happiness rating has a positive weight on the mental health score. Reward sensitivity score predicted mental health score, correcting for demographics (age, gender, qualifications, income, marital status) and IQ for experiments 1 (d), 2 (e) and 3 (f). Grey dots represent participants. Black dots represent the median of binned scores (for illustration purposes only). Error bars = s.e.m. Model prediction (of all data points) is represented by green line, with shaded areas corresponding to the 95% confidence bounds. β ± s.e.m. represent the linear regression (also including demographics) coefficients with the corresponding standard error and are tested against 0 using a two-sided t-test. Pers. ach., personal achievement.