Reacción a "Continued use of melatonin for insomnia is associated with an increased risk of heart failure"

Our understanding of melatonin as a treatment is based on reviews and meta-analyses, such as a recent one (2025) published by Daliri et al., which confirms in a systematic review the positive effect of melatonin on patient outcomes, in this case, in patients with heart failure, where the authors consider melatonin to be a new treatment for these cardiac patients, even in palliative care.

Its most precise indication is for jet lag, chronic insomnia in people over 55, and children with autism spectrum disorder. The current abstract by Ekenedilichukwu Nnadi et al. is an observational study based on data recorded in a UK and US database (TriNetX Global Research Network for adults ≥ 18 years with an insomnia diagnosis (ICD-10 F51.0)), which seriously questions the results of the reviews, associating an 89% higher risk of heart failure and hospitalisation with one year of melatonin use compared to patients who did not take melatonin.

There are clear limitations to the study, based on the fact that it is an observational study, knowing in advance that these studies only show association and do not establish causality. Furthermore, given that melatonin does not require a prescription in the US, it is possible that the control group (without melatonin) included many patients who take melatonin without a prescription (the percentage is unknown, which could be a very significant bias) and is not reflected in their medical records. Finally, it is an abstract from a conference and, unlike publications in indexed medical journals, has not been filtered by two independent reviewers.

Therefore, these findings challenge the perception of melatonin as a benign chronic therapy and only highlight the need for a prospective trial with a control group to clarify its safety profile.