The notion that the government should make day care more affordable has gained bipartisan traction in this election cycle, but studies suggest that extensive use of commercial day care facilities — especially for children younger than 3 — can do more harm than good in the long term.

What’s more, surveys indicate that most Americans are skeptical about outsourcing care for their children.

“Parents kind of instinctively know that especially little kids need time and attention,” said former domestic policy analyst Carrie Lukas, managing director of the Independent Women’s Forum.

With both of the major parties’ presidential nominees promising to help working families, affordable commercial child care has become an issue to attract voters.

Democratic nominee Hillary Clinton has said she would cap day care expenses at 10 percent of a family’s income and increase wages for industry workers to prevent high turnover rates. Republican nominee Donald Trump has introduced a plan to make child care expenses tax-deductible, and his aides have expressed interest in extending tax benefits to stay-at-home parents.

But researchers in child development and public policy question the wisdom of making commercial day care more affordable.

“I think it would be terrible for our kids,” said Steven Rhoads, a political scientist at the University of Virginia. “Studies indicate that there are real risk factors — anxiety, aggression, even when they get older, criminal behavior. It’s not a close call in most of these studies.”

Mr. Rhoads is the author of “Taking Sex Differences Seriously,” which examines the policy implications of biological differences between the sexes.

He recommends policies that allow families with children to keep more of what they earn. “It would be better to find ways to support families with young children more generally,” he said.

Ms. Lukas said any child care plan should allow parents to make whatever decision is right for them.

“We all want to make life easier on working parents, but I worry when you start just subsidizing child care,” she said. “It’s not really fair to families that are making different choices when it comes to child care, whether that’s working parents who try to work different hours so they can be home with kids or who make a real financial sacrifice so that they can keep a parent at home.”

Researchers from the National Bureau of Economic Research studied the effects of an affordable child care initiative in Quebec. By the year 2000, a $5-per-day day care policy had been implemented for all children younger than 5. The study, published in 2005, found that commercial day care was associated with health and behavioral problems in children.

The health problems were neither surprising nor new. Infants frequently put their hands into their mouths and share toys, and day care centers have long been associated with higher rates of infection. However, the study found that children in day care also exhibited higher rates of physical aggression and emotional anxiety.

A follow-up study last year found that the behavioral effects persisted into adolescence. Teens exposed to the Quebec day care program exhibited more emotional and behavioral problems, including anxiety, aggression and hyperactivity.

In addition, adolescent Quebecois had higher rates of crime compared with the general teenage population in Canada, and those exposed to day care programs had higher crime rates on average at every age than their peers.

One explanation for the findings is that children in day care produce elevated levels of the stress hormone cortisol, which is linked to higher rates of fear and anxiety.

A 2006 meta-analysis in Early Childhood Research Quarterly found that “the effect of day care attendance on cortisol excretion was especially noticeable in children younger than 36 months.”

“We speculate that children in center day care show elevated cortisol levels because of their stressful interactions in a group setting,” the study said.

A 2010 study conducted by University of Minnesota researchers noted that, during stages of rapid brain development in infancy, “contact with parents prevents elevations in cortisol, and this has been interpreted as nature’s way of protecting this developing brain from the potentially deleterious effects of this steroid.”

Adults with children in day care exhibited “more hostile, less consistent parenting” and “worse adult mental health and relationship satisfaction,” the 2005 Quebec study found.

Parental guilt and stress associated with day care, especially among mothers, are not simply a social stigma but rather an evolutionarily hard-wired response, Mr. Rhoads said.

“Mothers aren’t designed to be comfortable,” he said. “It’s not just social construction for the guilt, because mothers who worried or were anxious when their kid wasn’t in sight were more likely to have kids who thrived and made it through to the next generation.”

Other research paints a more complicated picture. In the United States, the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development followed 1,364 children from birth beginning in 1991. It found that children who spent more than 30 hours per week in day care were nine times more likely to exhibit behavioral problems by age 4 than their peers who spent less than 10 hours per week in child care.

The study also found that children who attended smaller day care centers with lower child-to-adult ratios and better-trained staff achieved some cognitive gains that lasted into adolescence — although behavioral problems persist regardless of day care quality.

A 2014 follow-up to the Quebec study by the Canadian Labor Market and Skills Researcher Network found that the age at which children enter day care was an important variable in determining the effect: The earlier children were exposed to day care, the worse they fared.

“The estimates indicate that, on average, children who gain access to subsidized child care at earlier ages experience significantly larger negative impacts on motor-social developmental scores, self-reported health status and behavioral outcomes including physical aggression and emotional anxiety,” the researchers said.

However, children 3 and older from disadvantaged backgrounds showed some behavioral benefits from attending day care.

Mr. Rhoads said there may be room for targeted day care assistance, although Republicans often express worry about giving incentives for negative behaviors.

“My argument would be maybe it’s different for single parents, but that’s very complicated,” he said. “Ages would also be very important. There’s no benefit before 3, and there are costs. So I would say there shouldn’t be subsidies for day care before the age of 3.”

A 2014 Pew Research Center poll found that 60 percent of Americans believe children fare better when one parent stays home. Only 16 percent of Americans in a 2013 Pew survey said it is best for children to have a mother who works outside the home full time.

“We should be thinking of ways to make child care more affordable for parents who need to use it, but the goal shouldn’t be to push more parents to make that choice,” Ms. Lukas said.