POTSDAM — Few people make it through life without spending at least one moment as a bully’s victim, but recent research suggests being a frequent bullying target may cause a life’s worth of medical problems.

Jennifer M. Knack, an assistant professor of psychology at Clarkson University, noticed that some victims of bullying and other aggressive acts suffer chronic health conditions.

“Most people experience peer aggression at some point in their lifetime, but there’s a difference between being the target of aggression and being the target of bullying,” she said. “Bullying is intentional. There is typically a power difference. Somebody has more power in a social group or hierarchy. They have more power or control over a situation.”

Ms. Knack’s bullying study was featured in the spring issue of the Journal of Applied Social Psychology. The study group involved adolescents and college students who answered questionnaires on bullying and health. The subjects also provided saliva samples so that Ms. Knack could measure their hormone levels.

“We’re seeing that being bullied is associated with having more health problems — stomach aches, sore throats, cold sores,” she said. “In college students, there are more serious health problems — bone conditions, joint conditions, heart problems.”

Ms. Knack’s research found that victims of social pain, such as bullying experience, elevated levels of cortisol — a hormone released in response to stress.

“Our theory is that it will have long-term implications,” she said. “It is going to change how your body reacts. It is more likely that you are going to have problems over a lifetime.”

Ms. Knack said higher cortisol levels lead to bone-related illness, heart disease and reduced immune system function.

The research also showed that young victims of prolonged bullying had unusually low levels of cortisol, but Ms. Knack could not explain why.

“It may be that the body learns to cope with the stress, so the cortisol levels stay low,” she said. “Those lower levels of cortisol are actually associated with more health problems in adolescents.”

Bullying is a component of human behavior whenever social groups, like cliques of students within a school, are formed, said Ms. Knack. The problem is neither new, nor rare.

“I’ve been finding my data matches some of the work others are doing,” she said. “About 10 to 30 percent of our students are experiencing this chronic bullying from once a week to a higher frequency.”

The next step is to extend the study to later stages in life. While other researchers are using study groups in offices or nursing homes, Ms. Knack wants to continue to monitor her test subjects.

“What I’d like to do over time is to follow people long term to see over time if there are developmental differences,” she said. “I am interested in the links with physical health effects.”

The research hopefully will contribute to greater awareness of bullying’s impact and treatments for its victims, Ms. Knack said.

“I think these people need somebody looking at this and being an advocate,” she said. “We are social creatures, but we are also very aggressive creatures. We are also able to regulate our behavior — we do it all the time, we put rules and norms in place. The same thing has to happen with bullying. Because of the media attention that we are having on bullying, we are starting to move toward that.”