BILLERICA — It’s a late summer afternoon, and the day is starting to drag for Jessica Doherty.

As she sits on her bed entranced by her iPad, her mother, Jeanne, seizes an opportunity to grab a moment for herself. Then, with a creak of her daughter’s bedroom door, the silence breaks.

Jessica, making guttural sounds as she shuffles into the dining room, reaches a table and slams it again, and again, and again.

“Use soft hands, Jessica. Soft hands,’’ her mother says, as she embraces her 21-year-old daughter.

Jessica is bored. But because of the effects of autism and Down syndrome, she struggles to communicate how she feels.

Normally, she would be in class or camp at the Kennedy Day School at Franciscan Children’s in Brighton. But for three weeks at the end of the summer — between the end of camp and start of her private day school — Jessica must stay at the family’s Billerica home.

Three weeks doesn’t sound like that much time. But for parents of children with complex intellectual, developmental, or medical needs, such breaks in care can lead to a digression in a child’s fragile mental state. They can also cost families hundreds or thousands of dollars in extra caregivers or lost time from work.

“When she’s at school or camp, you don’t usually ever see her go into a meltdown because all of her needs have been met,’’ Jeanne Doherty said. “But as each day goes by that she’s home, the frequency of meltdowns is more and more.’’

Filling a day with engaging activities is a common struggle for families of children with complex medical disabilities, said Maureen Gallagher, executive director of the Massachusetts Down Syndrome Congress, a support group for parents of children with Down syndrome and compounded conditions.

“I often hear of families who have to stay home, and they cannot go away on vacation or do the kinds of things that a family would typically like to do during this kind of down time,’’ Gallagher said.

As Jessica sat on the kitchen floor with her 23-year-old caretaker, taking a vacation is the last thing on Jeanne Doherty’s mind.

Jessica spent most of her summer physically and mentally stimulated at the school at Franciscan Children’s , where a collaboration of federal, state, and local district funding covers the cost.

The school cares for children ages 3 to 22 who need a range of medical rehabilitation and therapeutic services. More importantly, said John Nash, the president of the hospital, it gives them a place to come every day to learn and grow.

“The families have significant expenses to support these children,’’ Nash said. “The school is a location where they can bring their child, and know they can be safe, monitor their therapy, and help them gain confidence.’’

But when the camp ends, Jessica’s behavior becomes challenging and unpredictable, her mother said. Rather than measuring this break in weeks, Jeanne and her husband, John, said they must measure it in days, hours — minutes, even.

In the few weeks after camp, Doherty estimated that she will spend more than $1,000 on in-home support services for Jessica.

In order to receive more state funding, Doherty applied for aid through Adult Family Care — a MassHealth-funded program — which gives her about $60 a day to care for her daughter. But in just three hours on a recent day, she spent $85 — $45 for the caregiver at $15 an hour, $20 for the caregiver’s gas to come to the house and drive Jessica around, and another $20 for recreational activities. And on the days where none of her caretakers are available, Jeanne cannot work.

“Now it’s my turn to be the camp, and fill her days with people and things that would make her happy and keep her from going in a downward spiral of depression and anxiety,’’ Doherty said.

During breaks in outside care, eligible families can request state funds for emergency services and in-home clinical support, said Victor Hernandez, deputy assistant commissioner for the Department of Disability Services. Another available fund for eligible families is the Family Support Appropriation Account, which received a $5 million increase in this year’s state budget for the 11,000 families that care for their loved ones at home, Hernandez said.

But Hernandez said there is always a push for more money.

“There are some people who want the services spread out, and others who want it over a period of time,’’ he said. “We try to make it as flexible as possible. Each family is different.’’

For families in rural areas, such as that of Amy Mercier, who lives in a small town in the Berkshires with her husband and three children, extra care for her medically complex son is hard to come by.

Five-year-old William is deaf and blind, has autism and Down syndrome, and suffers from epilepsy.

In Mercier’s case, her son is integrated into the public school system. But after the district’s five weeks of summer care ends, she scrambles to fill up the time for her son to keep him physically and mentally stimulated.

“With any kid, you need to entertain them,’’ she said. “But for our kids, you run a special risk of regression. . . . If you’re talking about the difference between a kid communicating or not communicating — that’s a big deal.’’

On one sweltering July afternoon before camp at the Kennedy Day School ended, Jessica and her peers spent the morning at a dance party in the gym. Jessica flapped her arms to the music and continuously jerked her body, a sign she’s overwhelmed with joy, her family said.

Later that afternoon, she enjoyed homemade ice cream outside on the field, threw a ball in a game of shot put, and sat calmly during a music therapy class.

That day, her mother said, she came home elated and exhausted. She went straight to bed. No breakdowns, no outbursts. Her behavior was at her best.

But a few weeks later, her mother said, after spending a few days stuck in the house and in her own mind, Jessica “woke up mad at the world.’’

Story By Trisha Thadani | Globe Correspondent

Photos by Suzanne Kreiter | Globe Staff

Trisha Thadani can be reached at trishat@bu.edu. Follow her on Twitter@TrishaThadani.