When Jay Sullivan was 5 years old, his father had a “bipolar breakdown” and was sent to a psychiatric hospital. What Sullivan remembers from the days and years that followed are violent outbursts, putting his father to bed drunk, late-night calls when his father had nowhere to stay and bailing him out of jail.

“When he died in 1992, I put his ashes in my closet and put him behind me,” Sullivan wrote on his website.

But it wasn’t that simple. Three years ago, Sullivan, a professional photographer in Red Bank, NJ, began producing a series of images he calls “Glove” to try to reconnect with his father.

Sullivan photographed articles that had linked or divided the two of them — a baseball glove, his father’s shaver and black wingtip shoes and a prescription bottle containing lithium.

As Sullivan continued the project, the dark images of his father’s illness were gradually replaced by more positive ones — of his father’s successful business career, of the two of them going fishing together, and of trips to Yankee Stadium.

“Three years into this process and 20 years after his death, I have found the father I always wanted and in many ways always had,” Sullivan wrote.

Many of us understand the deep emotional connection Sullivan has with his father, even decades after his father’s death. But now a new body of research is explaining why we have that connection. Fathers, it turns out, contribute far more to their children than many of us realize.

Those contributions begin during pregnancy, before fathers and their children have even met. Studies show that the death rate of infants whose fathers were not around during pregnancy is nearly four times that of those with engaged dads. And depression in fathers during their partners’ pregnancies — which is more common than most people realize — can increase the child’s lifelong risk of depression.

After birth, children whose fathers play with them, read to them, take them on outings, and care for them have fewer behavioral problems during their early school years. And they have a lower risk of delinquency or criminal behavior as adolescents.

Some of fathers’ contributions are surprising. One might guess, for example, that mothers have more influence than fathers on their children’s language development. Despite the growing number of women in the workforce, mothers still spend more time with children in many families than fathers do.

But that turns out not to be the case. Lynne Vernon-Feagans of the University of North Carolina, who studies language development, has found that when it comes to vocabulary, fathers matter more than mothers.

In middle-class families, she found that parents’ overall level of education — and the quality of child care — were both related to children’s language development. But fathers made unique contributions to children’s language development that went beyond the contributions of education and child care.

When fathers used more words with their children during play, children had more advanced language skills a year later. And that is likely also linked with later success in school.

When fathers used more words with their children during play, children had more advanced language skills a year later. And that is likely also linked with later success in school.

And when Vernon-Feagans looked at poor families, she found much the same thing. She visited families when a child was 6 months old, 15 months old and 3 years old. She found that fathers’ education and their use of vocabulary when reading picture books to their children at 6 months of age were significantly related to the children’s expressiveness at 15 months and use of advanced language at age 3.

This held true no matter what the mother’s educational level was or how she spoke to the children.

“I do think our children see it as very special when they do book reading with their fathers,” Vernon-Feagans says. “They may listen more and acquire language in a special way.”

Several studies suggest that fathers also have a powerful influence on their daughters’ sexual behavior during adolescence.

This became clear in 2011 when Frayser High School in Memphis, Tenn., attracted national attention for its high pregnancy rate: About one in five of its female students was either pregnant or had recently given birth.

One local official blamed the high pregnancy rate on television shows such as MTV’s “16 and Pregnant” and “Teen Mom.” The official worried that these shows were encouraging Frayser’s female students to have unprotected sex earlier and more often.

That explanation seemed to make sense. But when psychologist Sarah E. Hill of Texas Christian University examined the situation, she noticed another striking fact: One in four households was headed by a single mother. Studies have revealed “a robust association between father absence — both physical and psychological — and accelerated reproductive development and sexual risk-taking in daughters,” she wrote.

The fathers’ absence in so many families was likely more important than what their daughters watched on television.

These are just a few of the many, many studies in recent years that have demonstrated a powerful link between fathers and their children.

They underscore what many of us experience — that our fathers are important in our lives, as photographer Sullivan discovered after his father’s death. And it underscores the hope that many fathers have — that they, in turn, will be important in their children’s lives.

Paul Raeburn is the author of “Do Fathers Matter? What Science Is Telling Us About the Parent We’ve Overlooked” (Scientific American), out this week.