Disturbances of social and affective processes are at the core of psychiatric disorders. Together with genetic predisposing factors, deprivation of social contact and dysfunctional relationships during development are some of the most important contributors to psychiatric disorders over the lifetime, while some developmental disorders manifest as aberrant social behavior early in life. That the cause of mental illness is rooted in the brain was long held as a truism, yet finding the causes for and neurobiological correlates of these conditions in the brain has proven and continues to be difficult (Venkatasubramanian G, Keshavan MS, Ann Neurosci 23:3–5. https://doi.org/10.1159/000443549, 2016). In clinical practice, psychiatric disorders are diagnosed based on categorical manuals, such as the DSM and ICD, which form a useful guide for clinical diagnosis and interventions. Yet, understanding the specific neural mechanisms leading to or characterizing distinct psychiatric conditions through this categorical approach has been slow (see, for example, Lynch CJ, Gunning FM, Liston C, Biol Psychiatry 88:83–94. https://doi.org/10.1016/j.biopsych.2020.01.012, 2020). Findings in the brain often do not seem to lend support to common mechanisms for the defined disorder categories. This is not particularly surprising because, in these diagnostic manuals, multiple combinations of symptoms can often lead to the same diagnosis, which is reflected in highly variable phenotypes of psychiatric disorders.