Physical abuse of children carries undeniable marks of pain, but in many cases the hidden scars associated with psychological abuse may be more detrimental in the long run, according to an American Academy of Pediatrics position statement published Monday in the journal Pediatrics.

Psychological abuse may be the most common form of child abuse and often the hardest to treat, according to the paper.

"This is an area easily overlooked because it's hard to articulate," said Ruth Anan, director of the early childhood program at the Center for Human Development at Beaumont Hospital in Royal Oak, Mich.

Many child health experts have grappled with properly identifying and defining the threshold for psychological abuse.

"We are talking about extremes and the likelihood of harm, or risk of harm, resulting from the kinds of behavior that make a child feel worthless, unloved or unwanted," said Dr. Harriet MacMillan, a professor in the departments of psychiatry and behavioural neurosciences and pediatrics at McMaster University's Michael G. DeGroote School of Medicine in Ontario, and an author of the paper.

Psychological abuse can range from depriving a child of social interactions to terrorizing. Single events of repetitive yelling were not defined as psychological abuse, according to MacMillan. Rather, abuse included ongoing events of belittling a child or consistent neglect, in each case "with or without the intention to harm," according to the paper.

Parents are most often the perpetrators and in many cases they do not know that their actions are considered abuse, many experts said.

The abuse, especially incurred within the first three years of life, can affect a child's development and lead to attachment disorder, delayed development, erratic behavior and socialization problems, according to the paper.

"The dose of abuse is an important factor to determine how severe the child's reaction will be," said Anon. "The frequency of the abuse and also the perpetrator and how influential they are in the child's life also affects the outcome."

More severe effects of the abuse may not be apparent in a child until much later.

"Children who are victims of emotional violence may appear totally normal when away from the family," said Dr. Astrid Heger, professor of clinical pediatrics at the University of Southern California Medical Center.

Previous studies suggest that nearly 9 percent of women and 4 percent of men in the UK and the U.S. have reported experiencing extreme psychological abuse during childhood.

Even when such psychological abuse is clearly defined in a clinical setting, many experts said it's difficult for children to receive the necessary intervention.

"The systems charged with the protection of children like to have physical evidence that abuse is occurring," said Heger. "They tend to see emotional abuse as nebulous and blurry and usually will not intervene."

A parent or other adults in the child's life are often the best people to help clinicians identify whether there is a problem, said Heger.

Some signals of abuse are detectable. Children exposed to psychological abuse are often hypervigilant or paranoid. They may also emulate the abusive behavior they are exposed to, said Heger.

"They also will react to other peers in the same manner that they are being treated at home," she said.

In many cases, identification of the problem and subsequent intervention require a group effort, said Dr. Karen Warman, associate professor of pediatrics at Montefiore Medical Center.

"Interdisciplinary support, including social workers and mental health professionals, is necessary to provide resources to help parents, or other caregivers, with healthy parenting," she said.

While prevention is often difficult depending on who the abuser is and the type of environment the child is raised, continual positive reinforcement by any adult in contact with the child may help a child overcome the potentially detrimental situation.

"Children should know that their feelings matter and that the adults in their life will protect them," said Warman.