Drs. Thomas and Lynette Long, the professors of education and researchers who popularized the term "latchkey children," have come up with new and worrisome findings about the differences in adolescent children who live with two parents versus those being raised by a single parent, and about the differences between those who return from school to empty homes versus those who go home to an adult.

The Longs' previous research has documented serious problems of anxiety, fears, loneliness and depression among elementary school children who spend substantial blocks of time alone at home in the mornings or afternoons while their parents work. The latest study was done of 400 older children who were in the seventh through 10th grades in parochial schools in the District and the suburban Maryland counties that are part of the Archdiocese of Washington.

The Longs' first study also was done of parochial school children, in part because they had easier access to Catholic schools since Tom Long teaches at Catholic University. (Lynette Long teaches at American University.)

Most of the children living with single parents lived with their mothers, Tom Long says. "What we found that I thought was particularly important was if the kid was a latchkey child living with a single head of household, when we asked them whether they were involved in sexual activity while they were home alone, nearly 40 percent said they were at some time involved in intercourse or petting, meaning with some type of nudity. You contrast this with kids who were living with two adults in the house, that was only 15 percent.

"Several things account for the difference," he says. "If you've got mom and dad versus the single parent, there's more likelihood that mom or dad is going to come home unannounced. With a single parent the kid just has to make sure mom isn't coming home.

"Most single parents aren't celibate. They're dating as well. So the child is living a lot closer to dating activity with a single parent than if he's living with a two-parent family. Working mothers, in order to bring in a satisfactory amount of income, work farther away from home to get better jobs. They have to carry more of the burden of operations of the household: grocery shopping, doing the laundry, plus their social life, which means that they would leave the child unattended for longer periods of time."

Long says that children who live with a single mother develop a "much closer relationship with the mother. The relationship with the absent father is a lot more distant." This, he believes, may foster a greater need for male companionship than if the child is living in a two-parent family.

Girls, the Longs found, are left unattended more of the time than boys are. "This might be partly because boys get involved with athletics so if they are on the football team they might have practice every day after school," says Tom Long. "Boys tend to be out more. Girls tend to be home more," in both single and two-parent families. "It logically follows that if you have the girl at home she may be at higher risk for unwanted pregnancy because the boy isn't going to be fooling around if he's out playing football."

In their research, they also measured depression among children left alone versus those who have a parent at home. "The scores were significantly different," says Long. "You'd find kids routinely left unattended are much more likely to score high on depression than those who always have a parent in attendance.

"Most parents assume that kids, once they get beyond the sixth grade, can be pretty independent. We look to kids to start baby-sitting around the age of 11 and most baby-sitters are between the ages of 11 and 14. Yet we're finding some characteristics of living that [suggest] you can't just assume that they can handle it on their own. They still need some adult supervision." He said they found that children whose mothers work part time seem to be "more like the kids who have mothers at home than the kids whose mothers work full time."

There are few after-school care programs that are appropriate for children between the ages of 12 and 15, says Long. If the Longs' findings are correct -- and simple common sense suggests they are -- these latchkey children face potentially disastrous consequences from being left alone. The Longs have done much to sound the alarm about the bad effects of leaving younger children alone, and communities have responded with extended day programs. They are sounding the same alarm about the dangers to adolescents, and the figures they offer suggest we'd better listen.