Money is normally discussed as an economic resource.
A new randomised experiment suggests it may also leave a measurable biological trace in young children.
Researchers followed families in the United States in which mothers with low incomes were randomly assigned shortly after giving birth to receive either US$333 per month or just US$20 per month.
Four years later, children whose mothers had received the larger payments showed a slightly slower pace on a DNA-based measure of biological ageing.
The difference was small, but because the families had been randomly assigned to the two payment groups, the researchers were able to make a stronger causal inference than is normally possible in studies linking poverty with children’s health.
The study, published on 8 September 2026 in Nature Human Behaviour, provides rare experimental evidence that changing a family’s financial resources can produce a detectable change in a biological marker measured in childhood.
But the result comes with an important warning.
The researchers do not yet know whether the epigenetic difference will persist, whether it means these children will actually age more slowly later in life or whether it will ultimately translate into better health.
The experiment began when the babies were born
The research forms part of the Baby’s First Years study, one of the first large randomised experiments in the United States designed specifically to test what happens when poverty is reduced during early childhood.
The project recruited 1,000 mothers whose household incomes were below the US federal poverty threshold from hospitals in New York City, New Orleans, Omaha and the Minneapolis-Saint Paul area.
Recruitment took place shortly after the women gave birth.
Four hundred mothers were randomly assigned to receive US$333 each month, while 600 received US$20 each month.
The payments were unconditional.
The researchers did not tell mothers to spend the money on food, education, housing or any other particular category.
It was deposited onto a debit card and families decided for themselves how to use it.
This is an important part of the study design because it allowed researchers to test the effect of additional income itself rather than the effect of a particular programme such as free meals, childcare or healthcare.
At age four, researchers looked at the children’s DNA
For the new analysis, researchers collected saliva samples from children at approximately four years old.
They were able to analyse DNA methylation data from around 735 children.
DNA methylation refers to chemical modifications attached to DNA that help regulate how genes are used.
The underlying DNA sequence is not being rewritten.
Instead, these chemical patterns can change in response to age, environment, stress, nutrition and other biological influences.
Scientists have learned to use combinations of these methylation patterns to construct what are sometimes called epigenetic clocks.
These tools attempt to estimate aspects of biological ageing that are not captured simply by counting how many birthdays a person has had.
The researchers used a measure called DunedinPACE
The main ageing measure was known as DunedinPACE.
Rather than estimating a person’s biological age as a single number, DunedinPACE is intended to capture the pace at which biological ageing is occurring.
In adults, faster DunedinPACE scores have been associated with poorer health, greater risk of age-related disease and mortality.
The researchers wanted to know whether four years of greater family income would affect this measure in children.
It did.
Children in families receiving the higher cash payment had DunedinPACE scores approximately 0.17 standard deviations lower than children in the low-cash group.
The statistical confidence interval only narrowly excluded zero, meaning this was not an enormous or overwhelmingly strong effect.
But it remained detectable after several sensitivity analyses.
Because the payment level had been randomly assigned years earlier, the result cannot easily be explained by the usual differences between poorer and wealthier families.
That distinction matters enormously in poverty research
Researchers have known for decades that poverty is associated with worse health outcomes.
Children growing up in lower-income households are, on average, exposed to more financial stress, housing instability, food insecurity, neighbourhood disadvantage and barriers to healthcare.
They also experience higher rates of several physical and mental health problems.
But observational studies face a fundamental difficulty.
Families with different incomes also differ in many other ways.
It can therefore be extremely difficult to determine whether income itself caused a health difference.
A randomised cash experiment approaches the problem differently.
The families did not end up in the high- and low-payment groups because of their education, health, motivation or existing financial behaviour.
They were assigned there by chance.
That makes the difference in the children’s ageing marker particularly noteworthy.
The study does not mean that poverty literally makes four-year-olds old
The phrase “biological ageing” can easily create the wrong impression.
These children were not physically ageing into adults faster or slower.
Researchers measured a molecular pattern that, particularly in adult populations, is associated with the rate of physiological ageing.
Scientists are still determining exactly what these epigenetic ageing measures mean during early childhood, when enormous biological changes are occurring naturally.
The new study therefore provides evidence of a difference in an ageing-related biomarker.
It does not show that children receiving more money will live longer.
It does not show that they will avoid disease later in life.
Those possibilities would require many more years of follow-up.
The researchers looked for signs that the biomarker already mattered
If the lower DunedinPACE score represented an immediate improvement in health or cognition, the researchers might have expected it to line up with other measures collected from the children.
That largely did not happen.
The children’s DunedinPACE scores were not significantly associated with their executive functioning, receptive vocabulary, body mass index, maternal reports of general health or the brain-activity measures examined by the researchers.
This is one of the most important limitations of the finding.
The biological difference is measurable.
Its practical meaning for a four-year-old child is not yet clear.
Cash did not improve every biological measure
The researchers also examined another DNA-methylation measure known as Epigenetic-g.
It was developed as a biomarker associated with cognitive functioning.
The researchers had predicted that children in the higher-cash group might score higher on this measure.
They did not find convincing evidence supporting that hypothesis.
Results were inconsistent across different analyses.
Two other commonly used epigenetic ageing measures, GrimAge and PhenoAge acceleration, also did not differ meaningfully between the two cash groups.
This makes the study more specific than a headline such as “money improves children’s DNA” would suggest.
One preregistered biological ageing measure changed.
Several others did not.
The mothers did not show the same effect
The research team also analysed epigenetic measures in the mothers.
There was no clear evidence that receiving the higher cash payment changed the mothers’ DunedinPACE scores or the other principal epigenetic measures examined.
That difference between mothers and children may be important.
The first few years of life are an unusually rapid period of development.
Organs, the immune system, metabolism and the brain are all undergoing substantial change.
Researchers have therefore proposed that early childhood may represent a particularly sensitive period during which environmental conditions can leave measurable biological effects.
The current experiment is consistent with that possibility, although it does not establish exactly why the children responded while their mothers did not.
How could money possibly influence a child’s cells?
There is unlikely to be one mechanism.
Money changes environments.
A family with more financial flexibility may be able to buy more food, choose different housing, pay bills more reliably, afford transport, purchase children’s books or toys, spend money on childcare or simply experience fewer moments of acute financial pressure.
Previous research from the same Baby’s First Years experiment has found that mothers receiving the larger payments changed some of their spending and parenting-related activities.
But the researchers cannot currently point to one pathway and say that it caused the epigenetic effect.
Stress may be involved.
Nutrition may be involved.
Housing or environmental exposures may matter.
Changes in parent-child interactions could contribute.
Several smaller pathways may operate simultaneously.
There is an important difference between giving money and prescribing behaviour
The study is also notable because the intervention did not require participants to behave in a particular way.
Many programmes attempting to improve child development are highly targeted.
Parents may receive nutritional advice, parenting classes, educational materials or access to specialised services.
Those interventions can be valuable.
But an unconditional cash transfer starts from a different assumption: families themselves may know which immediate needs are most important.
For one household, an additional payment could mean groceries.
For another, it may prevent electricity from being disconnected.
For another, it could cover transport, nappies, rent or childcare.
The biological result suggests that altering the family’s overall resource environment may itself matter, even without researchers prescribing exactly how the money must be used.
Previous results from the same experiment have been mixed
It is equally important not to portray Baby’s First Years as producing uniformly positive outcomes.
Earlier analyses have found some changes in parental spending, activities with children and particular measures of children’s brain activity.
But other predicted effects have not appeared.
For example, research examining mothers’ reports of children’s language and socio-emotional development during the first three years found no statistically detectable advantage from the higher cash payments.
A 2026 study of brain activity at age four also found no effect on its main preregistered EEG measure, although exploratory analyses identified a difference in alpha-wave activity.
This is normal in large, long-running experiments.
A social intervention does not need to improve every measured outcome to produce meaningful effects in some areas.
But it also means individual positive findings should not be presented as evidence that cash automatically transforms child development.
The South African comparison is impossible to ignore
The findings are especially relevant to countries in which cash grants already form an important part of social policy.
South Africa’s Child Support Grant is one of the country’s largest social assistance programmes.
As of April 2026, the standard Child Support Grant is R580 per month per eligible child.
The South African system is not equivalent to the US experiment.
Eligibility rules differ.
The economic environments are different.
The size of the transfers relative to household income is different.
South African families also face different housing, healthcare, education and labour-market conditions.
It would therefore be inappropriate to claim that increasing the Child Support Grant would reproduce the same epigenetic effect.
But the new experiment does add something important to the policy discussion.
Cash assistance is usually assessed through outcomes such as poverty rates, food expenditure and household consumption.
The possibility that income support can also produce measurable biological effects during early childhood widens the question of what social protection may influence.
The study does not tell governments how much money to give
There is another limitation for policymakers.
The trial compared two particular payment levels.
It does not establish a universal threshold above which children’s biology improves.
Nor can researchers conclude that doubling the payment would double the biological effect.
The relationship between income and development is unlikely to work that neatly.
An extra amount of money may matter greatly to a household struggling to afford basic food or rent but much less to a household whose essential needs are already comfortably met.
The economic context therefore matters as much as the nominal amount.
The children will need to be followed for years
The most important unanswered question is what happens next.
DunedinPACE has a strong research history in adults, where faster scores are associated with poorer later-life outcomes.
Its interpretation in four-year-old children is much newer.
If the difference between the cash groups remains visible as the children grow older and begins to predict physical health, cognition or other developmental outcomes, the policy implications would become considerably stronger.
If the difference disappears or proves unrelated to later health, the interpretation would be much more modest.
The Baby’s First Years project is continuing to follow participating families, providing an opportunity to answer some of those questions.
A small molecular change can still matter scientifically
The effect found in the study was not large.
That is worth stating clearly.
The statistical result was also considerably less dramatic than the idea that “cash slows ageing” might suggest.
Yet scientifically, the randomised design makes the finding unusual.
Much of what researchers know about poverty and biology comes from observing differences that already exist between populations.
This experiment altered one important part of children’s environments deliberately: the amount of money their mothers received each month.
Four years later, a biological difference could be detected.
That does not settle the debate over cash transfers, poverty policy or child development.
But it makes one point considerably harder to dismiss.
Economic conditions do not exist only in bank accounts.
During the earliest years of life, they may become measurable in biology too.
Source Information
Primary Study: Effects of a randomized controlled trial of unconditional cash transfers on epigenetic measures of ageing and cognition in children and mothers
Lead Authors: Laurel Raffington, Yayouk E. Willems, Jessica F. Sperber and Sepideh Zarandooz et al.
Journal: Nature Human Behaviour
Published: 8 September 2026
Study: Baby’s First Years randomized controlled trial
Original trial sample: 1,000 mothers with incomes below the US federal poverty threshold
High-cash group: US$333 per month
Low-cash group: US$20 per month
Child epigenetic analysis: Approximately 735 four-year-old children
Primary ageing result: −0.17 standard deviation difference in DunedinPACE in the high-cash group
DOI: 10.1038/s41562-026-02568-4
South African Context: South Africa’s Child Support Grant increased to R580 per month per eligible child from April 2026, according to the 2026 National Budget and the South African Social Security Agency.
