Scientists don't have a lot of experience when it comes to spotting borderline personality disorder in children because it was originally believed to be a problem only suffered by people after adolescence. Most experts who've studied the subject suggest that children suffering from this disorder can be extremely moody from a very early age. They will often overreact to anything that happens, and they may be extremely unwilling to deal with any kind of correction. These children will also frequently be quick to suddenly turn on close friends and may go from loving them to totally hating them and then back to adoring them again.
Most of the symptoms that manifest with borderline personality disorder in children are also seen in adults, but they may emerge in different ways. Adult people with this disorder often have a great deal of trouble controlling their reactions to things. If they become angry at someone, they might not be able to effectively deal with the impulse to get revenge. They also see everyone in a love or hate kind of way because they are unable to perceive the subtleties and contradictions in the personalities of others.
One of the main signs of borderline personality disorder in children that shows up earliest is mood swings. The children will often switch from happy to sad much more often than normal children do. They may also seem to experience their emotions in a more extreme way. So, when they become angry, they may be violent or break things, and when happy, they can sometimes take that to extremes as well.
Another common symptom with borderline personality disorder in children is an overreaction to punishment. This may stem from the child's inability to hold a contradictory view of his or her parents. Before the punishment, the child may adore the parents completely, but after the punishment, the parent becomes a figure to be hated totally. Eventually, something else happens to change the child's mind, and the parent is in his good graces again. The children may also be prone to bouts of self-hatred, and these can lead to attempts at self-injury.
Children with borderline personality disorder may break rules frequently because of their impulsiveness. These problems with self-control often cause them a lot of trouble in school, and their teachers may complain about disciplinary issues. Later in life, they can lead to much more dangerous behaviors, including a tendency to break the law, sometimes violently.