Lähteenvuo et al1 present an analysis of Finnish national registers with the question of which psychotropic drugs reduce the need for rehospitalization in people with bipolar disorder. Psychiatry is currently seeing a wave of such analyses, which, in part, might reflect the limitations of randomized clinical trials (RCTs). While RCTs are considered to be the gold standard because only randomization can rule out both known and unknown confounders, their limitations include trial populations that are not representative of the real world, trials that are typically short term, and outcomes that, in RCTs focused on the maintenance of patients with chronic disease, include only worsening of symptoms rather than full-blown rehospitalization. The analyses of national cohorts overcome these problems by examining all patients in 1 country who are followed up for several years, who can then contribute to very large sample sizes.