Does the "Blue Light" for Newborn Jaundice Cause Cancer? What a Large 2025 Study Really Found

A plain-language guide to Freeman and colleagues' review of 15 studies and nearly 6.7 million children

A large 2025 review that combined 15 studies and nearly 6.7 million children found that babies treated with phototherapy for newborn jaundice had a slightly higher chance of being diagnosed with cancer later in life—about a 24% increase in the odds. That sounds alarming, but in real numbers it works out to roughly 51 extra cases per 100,000 treated children, and some of that small increase is probably explained by the jaundice itself rather than the light. Set against the serious, permanent brain injury that phototherapy prevents, the treatment remains clearly worth it when a baby needs it.

Why This Question Matters

Newborn jaundice—the yellowing of a baby's skin and eyes—is one of the most common conditions in the first days of life. It happens because of a substance called bilirubin, a normal byproduct of the body breaking down old red blood cells. Newborns often can't clear bilirubin fast enough, so it builds up. For most babies this is mild and harmless, but when bilirubin climbs too high it can cross into the brain and cause damage. The standard, decades-old treatment is phototherapy: placing the baby under special blue-green lights that change the bilirubin into a form the body can easily get rid of ^[1].

The reason doctors treat jaundice so carefully is that the alternative can be devastating. If very high bilirubin is left untreated, it can cause a permanent condition called kernicterus, which can lead to a form of cerebral palsy, hearing loss, and problems with eye movement ^[2]. These injuries cannot be reversed. Phototherapy is one of the great success stories of newborn care precisely because it prevents them simply, safely, and cheaply.

A Worry That Goes Back Decades

Even though phototherapy is very safe, scientists have wondered for a long time whether the light might have any hidden downside. As far back as 1979, researchers raised the possibility that the light energy could subtly damage DNA, the genetic material inside cells, and they described phototherapy as a "potential environmental health hazard" worth studying ^[3]. Because so many babies receive the treatment—European studies show close to 4% of newborns are treated, and jaundice is a leading reason babies are brought back to the hospital in their first week ^[4]—even a very small risk would be worth understanding.

This careful attitude is also why treatment guidelines have become more conservative over time. In 2022, the American Academy of Pediatrics updated its recommendations and raised the bilirubin levels at which phototherapy is advised, meaning fewer babies now qualify for treatment. After the change, one large hospital network reported a 47% drop in phototherapy use, with only about 2% of newborns being treated ^[5]. In other words, doctors were already moving toward using phototherapy only when it is truly needed. The 2025 study arrives in that context—not to frighten parents, but to give clear numbers to a question families increasingly ask.

What the Researchers Did

A team led by Freeman and colleagues gathered every suitable study they could find on phototherapy and later cancer, published between 1970 and 2025 ^[6]. They combined 15 studies covering 6,675,265 children, some followed all the way into their twenties and one group up to age 31. This kind of study, called a meta-analysis, pools many smaller studies together so that patterns too small to see in any single one become visible. The researchers also graded how trustworthy each study was: eight were high quality, one had some concerns, and six had weaknesses—mainly because they did not fully account for other factors that could muddy the results.

What They Found

Overall, children who had received phototherapy had about a 24% higher chance of a cancer diagnosis than those who had not. Put into everyday terms, that means roughly 51 additional cancer cases for every 100,000 children treated, spread over more than a decade of childhood. The small increase showed up mostly in blood cancers such as leukemia, and to a lesser degree in cancers of solid organs. Reassuringly, there was no meaningful increase in skin cancer, which is often the first thing parents worry about with a light-based treatment ^[6].

What the Findings Actually Mean

Here is the most important thing to understand: this study found an association, not proof that phototherapy causes cancer. That distinction matters. All of the studies were observational, meaning researchers simply compared children who happened to receive phototherapy with those who didn't—they did not run a controlled experiment. The trouble is that babies who need phototherapy are different in other ways: they have higher bilirubin, and they are more often born premature or with other health conditions, all of which can independently affect cancer risk. So part of the small extra risk may come from the underlying jaundice or prematurity, not the light itself. The researchers point out that high bilirubin on its own may carry a small cancer association, and that laboratory studies show phototherapy can cause temporary DNA changes in blood cells ^[7]—changes that other research suggests fade within a few years.

The second key point is about keeping the numbers in perspective. A 24% increase sounds large, but childhood cancer is rare to begin with, so a 24% increase of a very small number is still a very small number—about 51 extra cases per 100,000 children. Compare that with what phototherapy prevents. Untreated severe jaundice can permanently damage a developing baby's brain and vision ^[8], and the resulting condition, kernicterus, is exactly the kind of injury that modern brain research is trying to understand and prevent ^[9]. Thanks to phototherapy and careful monitoring, this severe brain injury now happens to only about 1 in 50,000 to 100,000 babies. Choosing to skip needed phototherapy to avoid a tiny, uncertain cancer risk would mean accepting a rare but catastrophic and preventable brain injury instead. That is not a good trade, and it is not what the researchers recommend.

What This Means for Families

If your baby needs phototherapy, this study is not a reason to refuse or fear it. The clear takeaway from the researchers is that phototherapy should still be used whenever a baby's bilirubin reaches the level where treatment is recommended—the benefit far outweighs the small possible risk. What the study does support is a sensible principle doctors already follow: use phototherapy only when it is truly needed, and only for as long as needed. Laboratory studies suggest that stronger and longer light exposure causes more DNA changes ^[10][11], so using the least treatment necessary to bring bilirubin safely down is the wise approach—and it is already standard practice.

It can help to picture the numbers with a simple comparison. Imagine two large groups of 100,000 children each—one group treated with phototherapy as newborns, one group not. Over the following decade or more, the study suggests there might be roughly 51 more cancer diagnoses in the treated group. At the same time, in a world without phototherapy, far more children in the untreated group would suffer permanent brain damage from severe jaundice, because there would be no safe way to bring dangerously high bilirubin down. When you line the two risks up side by side, the balance is not close: the treatment prevents a common and devastating harm while carrying only a small and uncertain one. And because some of that small cancer signal is likely due to the jaundice and prematurity themselves rather than the light, the true risk from phototherapy alone may be even smaller than the numbers suggest.

It is also reassuring that the increase did not appear in skin cancer, which is often parents' first instinct with any light treatment. The small signal was mostly in blood cancers such as leukemia—but even there, the same caution applies, because the children who needed phototherapy were also more likely to have been born early or been sicker at birth. Importantly, nothing in this research means that a child who had phototherapy needs extra cancer checks or screening. Their pediatric care should simply continue as normal.

If you find yourself worried after reading headlines online, it is completely reasonable to ask your baby's care team about it. A helpful way to think about the conversation is to ask not just "is the treatment risky?" but "what happens if we don't treat?" The honest answer is that the danger of untreated high bilirubin is real, immediate, and far larger than the small, uncertain, long-term signal seen in these pooled studies.

What Researchers Are Working on Next

Scientists want to sharpen these answers. Future studies will try to separate the effect of the light from the effect of the jaundice itself by carefully accounting for how sick each baby was, and will record exactly how much light each baby received so they can see whether more treatment means more risk. Premature babies are a special focus, because they have thinner skin and often need longer treatment, and they were underrepresented in the studies so far. Until those answers arrive, the guidance for families is steady and reassuring: when a baby needs phototherapy, it remains a safe, effective, and life-changing treatment, and the small cancer signal in the research does not change that.

References

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2. Shapiro SM, Popelka GR. Auditory impairment in infants at risk for bilirubin-induced neurologic dysfunction. Semin Perinatol. 2011;35:162–170. doi:10.1053/j.semperi.2011.02.011 ↩
3. Speck WT, Rosenkranz HS. Phototherapy for neonatal hyperbilirubinemia—a potential environmental health hazard to newborn infants: a review. Environ Mutagen. 1979;1:321–336. doi:10.1002/em.2860010404 ↩
4. van der Geest BAM, de Mol MJS, Barendse ISA, de Graaf JP, Bertens LCM, Poley MJ, et al. Assessment, management, and incidence of neonatal jaundice in healthy neonates cared for in primary care: a prospective cohort study. Sci Rep. 2022;12:14385. doi:10.1038/s41598-022-17933-2 ↩
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7. Aycicek A, Kocyigit A, Erel O, Senturk H. Phototherapy causes DNA damage in peripheral mononuclear leukocytes in term infants. J Pediatr (Rio J). 2008;84:141–146. doi:10.2223/JPED.1765 ↩
8. Good WV, Wong RJ, Norcia AM, Hou C, Cellucci J, McGovern MQ, et al. Effect of bilirubin on visuocortical development in preterm infants. J Perinatol. 2025;45:1289–1296. doi:10.1038/s41372-025-02213-4 ↩
9. Pranty AI, Shumka S, Adjaye J. Bilirubin-induced neurological damage: current and emerging iPSC-derived brain organoid models. Cells. 2022;11(17):2647. doi:10.3390/cells11172647 ↩
10. Karadag A, Yesilyurt A, Unal S, Keskin I, Demirin H, Uras N, et al. A chromosomal-effect study of intensive phototherapy versus conventional phototherapy in newborns with jaundice. Mutat Res. 2009;676:17–20. doi:10.1016/j.mrgentox.2009.03.008 ↩
11. Ramy N, Ghany EA, Alsharany W, Nada A, Darwish RK, Rabie WA, et al. Jaundice, phototherapy and DNA damage in full-term neonates. J Perinatol. 2016;36:132–136. doi:10.1038/jp.2015.166 ↩