There is an estimated two percent of the population that is living with borderline personality disorder. This disorder is thought to be caused by a variety of things, including genetic makeup, neurotransmitters, neurobiology and traumatic events that have occurred in a person's lifetime. Borderline personality disorder is more common than bipolar disorder and schizophrenia, disorders which are often given more attention. Borderline personality disorder is characterized by the instability of moods, relationships, self-image and behavior. Borderline personality disorder is very severe and can lead to suicidal thoughts and behavior, substance abuse, trouble keeping relationships, and a variety of serious side effects. Genetically speaking, scientists have many reasons to believe that genes are a prime source of the disorder. A recent study done on a set of twins, found that if one twin had the disorder, there was a two in three chance the other twin would also develop borderline personality disorder. Borderline personality disorder can be inherited by parents, or other relatives who may suffer, that are emotionally prone to change and very harsh and aggressive. Scientists also have reason to believe it can be a developed trait. Low levels of serotonin, a neurotransmitter, can also be linked to the cause of borderline personality disorder. If the human body is running low on serotonin, a person can become severely depressed and angry, with tendencies to show aggression and act out. Two other neurotransmitters, dopamine and noradrenalin, can also have the same effect as serotonin, when the body is running low. Neurobiology can also be a cause of borderline personality disorder. MRI scanners have been used multiple times for a detailed image of the brain, and other parts of the body. In patients with borderline personality disorder, there were three parts of the brain that stood out during one MRI scan; the amygdala, hippocampus and orbitofrontal cortex. The amygdala regulates emotions, while the hippocampus helps regulate behavior and the orbitofrontal cortex helps plan and make decisions. Each of the three area's regulations are all things borderline personality disorder patients have a hard time dealing with. Other factors that can cause borderline personality disorder are environmental. Most patients have been victims of emotional, physical or sexual abuse, have been exposed to fear as a child, been neglected by their parents and families, or have grown up with another relative that has suffered a serious mental health condition. The family and environment a child grows up in, has a serious effect on whether or not they will suffer from this disorder. If an adult has bad memories of their childhood, or unresolved anger and fears, these thinking patterns can lead to borderline personality disorder.