1. Piketty, T. Capital in the Twenty-first Century (Belknap Press, Cambridge, MA, 2014).

2. Kawachi, I. & Kennedy, B. P. The Health of Nation: Why Inequity is Harmful to Your Health (The New Press, New York, NY, 2002).

3. Wilkinson, R. G. & Pickett, K. E. Income inequality and population health: a review and explanation of the evidence. Soc. Sci. Med. 62, 1768–1784 (2006).

4. Marmot, M. G. et al. Health inequalities among British civil servants: the Whitehall II study. The Lancet 337, 1387–1393 (1991).

5. Hamad, R., Fernald, L. C., Karlan, D. S. & Zinman, J. Social and economic correlates of depressive symptoms and perceived stress in South African adults. J. Epidemiol. Community Health 62, 538–544 (2008).

6. Stansfeld, S. A., Head, J., Fuhrer, R., Wardle, J. & Cattell, V. Social inequalities in depressive symptoms and physical functioning in the Whitehall II study: exploring a common cause explanation. J. Epidemiol. Community Health 57, 361–367 (2003).

7. Turner, R. J., Lloyd, D. A. & Roszell, P. Personal resources and the social distribution of depression. Am. J. Community Psychol. 27, 643–672 (1999).

8. Jang, K. L. The Behavioral Genetics of Psychopathology: A Clinical Guide (Lawrence Erlbaum Association, Mahwah, NJ, 2008).

9. Messick, D. M. & McClintock, C. G. Motivational bases of choice in experimental games. J. Exp. Soc. Psychol. 4, 1–25 (1968).

10. Van Lange, P. A. M. The pursuit of joint outcomes and equality in outcomes: an integrative model of social value orientation. J. Pers. Soc. Psychol. 77, 337–349 (1999).

11. Gospic, K. et al. Limbic justice—amygdala involvement in immediate rejection in the Ultimatum Game. PLoS Biol. 9, e1001054 (2011).

12. Haruno, M. & Frith, C. D. Activity in the amygdala elicited by unfair divisions predicts social value orientation. Nat. Neurosci. 13, 160–161 (2010).

13. Haruno, M., Kimura, M. & Frith, C. D. Activity in the nucleus accumbens and amygdala underlies individual differences in prosocial and individualistic economic choices. J. Cog. Neurosci. 26, 1861–1870 (2014).

14. Groenewold, N. A., Opmeer, E. M., de Jonge, P., Aleman, A. & Costafreda, S. G. Emotional valence modulates brain functional abnormalities in depression: evidence from a meta-analysis of fMRI studies. Neurosci. Biobehav. Rev. 37, 152–163 (2013).

15. Matthews, S. C., Strigo, I. A., Simmons, A. N., Yang, T. T. & Paulus, M. P. Decreased functional coupling of the amygdala and supragenual cingulate is related to increased depression in unmedicated individuals with current major depressive disorder. J. Affect. Disord. 111, 13–20 (2008).

16. Bremner, J. D. et al. Hippocampal volume reduction in major depression. Am. J. Psychiatry 157, 115–118 (2000).

17. Lorenzetti, V., Allen, N. B., Fornito, A. & Yücel, M. Structural brain abnormalities in major depressive disorder: a selective review of recent MRI studies. J. Affect. Disord. 117, 1–17 (2009).

18. Sheline, Y. I., Wang, P. W., Gado, M. H., Csernansky, J. G. & Vannier, M. W. Hippocampal atrophy in recurrent major depression. Proc. Natl Acad. Sci. USA 93, 3908–3913 (1996).

19. Nestler, E. J., Hyman, S. E. & Malenka, R. J. Molecular Neuro-pharmacology. A Foundation for Clinical Neuroscience 2nd edn (McGraw-Hill, New York, NY, 2009).

20. Akiskal, H. S., Hirschfeld, R. M. & Yerevanian, B. I. The relationship of personality to affective disorders. Arc. Gen. Psychiatry 40, 801–810 (1983).

21. Von Zerssen, D., Tauscher, R. & Possl, J. The relationship of premorbid personality to subtypes of an affective illness. A replication study by means of an operationalized procedure for the diagnosis of personality structures. J. Affect. Disord. 32, 61–72 (1994).

22. Güth, W., Schmittberger, R. & Schwarze, B. An experimental analysis of ultimatum bargaining. J. Econ. Behav. Organ. 3, 367–388 (1982).

23. Sanfey, A. G., Rilling, J. K., Aronson, J. A., Nystrom, L. E. & Cohen, J. D. The neural basis of economic decision-making in the ultimatum game. Science 300, 1755–1758 (2003).

24. Beck, A. T., Steer, R. A., Ball, R. & Ranieri, W. Comparison of Beck Depression Inventories -IA and -II in psychiatric outpatients. J. Pers. Assess. 67, 588–597 (1996).

25. Tricomi, E., Rangel, A., Camerer, C. & O’Doherty, J. Neural evidence for inequality averse social preferences. Nature 463, 1089–1091 (2011).

26. Schmaal, L. et al. Subcortical brain alterations in major depressive disorder: findings from the ENIGMA Major Depressive Disorder working group. Mol. Psychiatry 21, 806–812 (2016).

27. Michl, P. et al. Neurobiological underpinnings of shame and guilt: a pilot fMRI study. Soc. Cogn. Affect. Neurosci. 9, 150–157 (2014).

28. Doerig, N. et al. Neural representation and clinically relevant moderators of individualised self-criticism in healthy subjects. Soc. Cogn. Affect. Neurosci. 9, 1333–1340 (2014).

29. Eldar, E. & Niv, Y. Interaction between emotional state and learning underlies mood instability. Nat. Commun. 6, 6149 (2015).

30. Eldar, E., Rutledge, R. B., Dolan, R. J. & Niv, Y. Mood as representation of momentum. Trends Cogn. Sci. 20, 15–24 (2016).

31. Headey, B. & Veenhoven, R. in How Harmful is Hapiness? Consequences of Enjoying Life or Not (ed. Veenhoven, R.) 106–127 (Universitaire Pers, Rotterdam, 1989).

32. Drysdale, A. T. et al. Resting-state connectivity biomarkers define neurophysiological subtypes of depression. Nat. Med. 23, 28–38 (2017).

33. Ogawa, T. & Oda, M. Construction and Evaluation of the Facial Expression Database ATR Technical Report TR-H-244 (1998).

34. Bishop, C. M. Pattern Recognition and Machine Learning (Springer, New York, NY, 2006).

35. Shawe-Taylor, J. & Cristianini, N. Kernel Methods for Pattern Analysis (University Press, Cambridge, 2004).

36. Tipping, M. E. Sparse bayesian learning and the relevance vector machine. J. Mach. Learn. Res. 1, 211–244 (2001).