According to
Google Scholar, Licinio has an h-index of 86, with 38,965 citations. He has published 309 papers indexed in PubMed, as well as 13 books. Licinio is known for his research into
leptin and its role in conveying a feeling of
satiety. For example, in 2002, he identified three people from
Turkey who suffered from a genetic disorder called
leptin deficiency – the only three adults known at that time to have this disorder – all of whom were severely overweight as a result. He then administered daily leptin injections to each of them, and found that after ten months, the patients had lost half of his or her original body weight. He discovered that despite being produced by a dispersed mass of fat cells,
leptin is secreted in a highly organised manner with distinct pulsatility and circadian rhythm and that it appears to regulate the minute-to-minute rhythms of several endocrine axes, such as the
hypothalamic-pituitary-adrenal axis, the
hypothalamic–pituitary–thyroid axis, and the
hypothalamic–pituitary–gonadal axis. Licinio and his colleagues were the first to suggest that
leptin may have
antidepressant effects, a concept that was subsequently extended by other groups. He also contributed to pioneer the concept that leptin has pro-cognitive effects in humans. With his group, Licinio conducted work on the
precision medicine and
pharmacogenomics of depression that started in 2000 as part of the
National Institute of General Medical Sciences NIH Pharmacogenomics Research Network (PGRN). In that project, he and his team studied a Mexican-American population with
major depressive disorder in the city of Los Angeles, in the context of an extensive process of community engagement, which received Certificates of Commendation both from the
California State Legislature and the
United States Congress. He contributed the Mexican American samples to the
International HapMap Project. His pharmacogenetics research has resulted in several publications on predictors of antidepressant treatment response in this population. Wong and Licinio contributed some of the earliest work on the role of
cytokines and immune mediators in the brain, with implications for the underlying biology of
major depressive disorder, and published scientific articles on the localisation of gene expression for
interleukin 1 receptor antagonist,
interleukin 1 receptor, type I (IL1R1), also known as CD121a (Cluster of Differentiation 121a), and inducible
nitric oxide synthase (iNOS) in mammalian brain. They also showed that
interleukin 1 receptor antagonist is an endogenous neuroprotective agent. They have shown that the central and peripheral
cytokine compartments are integrated but differentially regulated. In collaboration with colleagues at
Columbia University Licinio and his team showed that inflammation-mediated up-regulation of secretory
sphingomyelin phosphodiesterase in vivo represents a possible link between inflammatory
cytokines and
atherogenesis. Licinio's line of research examining the effects of peripheral
inflammation in brain,
behaviour and
metabolism is ongoing in their lab. In a more recent and ongoing line of research, Licinio and collaborators are examining the effects of the
human microbiota and the microbiome–gut–brain (MGB) axis in obesity with diabetes and on behaviors relevant to depression and schizophrenia, an emerging area which opens potentially novel avenues for the treatment of psychiatric disorders. Licinio and Wong have recently published a paper on the effects of climate change on mental health, which Springer Nature highlighted as the leading article for their Sustainable Development Goal (SDG) 13: Climate Action. == Public engagement ==