Neuroscience studies into psychiatric disorders generally rely on disease definitions that are based on the influential Diagnostic and Statistical Manual of Mental Disorders (DSM), the fifth edition of which (DSM-5) was released earlier this year. Designed as a purely diagnostic tool, the DSM considers different disorders as distinct entities. However, boundaries between disorders are often not as strict as the DSM suggests. To provide an alternative framework for research into psychiatric disorders, the US National Institute of Mental Health (NIMH) has recently introduced its Research Domain Criteria (RDoC) project. In the RDoC, five 'domains' each reflect a brain system in which functioning is impaired, to different degrees, in different psychiatric conditions. Nature Reviews Neuroscience asked six leading investigators for their thoughts on how DSM-5 and the RDoC will influence neuroscience research into psychiatric disorders.