Mood disorders, including major depressive disorder (MDD) and bipolar disorder (BD), are highly prevalent, frequently disabling, and sometimes deadly. Additional research and more effective medications are desperately needed, but clinical trials research in mood disorders is fraught with ethical issues. Although many authors have discussed these issues, most do so from a theoretical viewpoint. This manuscript uses available empirical data to inform a discussion of the primary ethical issues raised in mood disorders research. These include issues of consent and decision‐making capacity, including patients’ motivations for participating in research. We also address drug withdrawals, placebo controls, and the overall safety of research. Finally, we examine the extant literature for studies discussing potential indirect benefits of clinical trials research to participants. Taken together, the evidence suggests that clinical trials research incorporating drug withdrawals and placebo controls can be conducted safely and ethically, even in patients with severe or treatment‐resistant mood disorders. In fact, given the dearth of effective treatment options for this population, it is our opinion that a moral imperative exists to extend the offer of research participation to severely ill or treatment‐resistant groups.