Answer:
childhood traumas
Step-by-step explanation:
Borderline once was a very rare or unusual condition that had no clear source or genesis and it was diagnosed mainly in females.
The studies showed began to see that major traumas during childhood years like sexual and physical violence and other forms of abuse made the personality disorder be more likely.
Today psychiatrists will often see how Borderline will result as a condition of both genetics and the traumatic experiences that will trigger this mental health condition.
A combination of both the environment and the genes will cause brain structure to malfunction and often social situations will be a root cause of the appearance of the borderline personality disorder
Any abuse in childhood years will often later in life manifest as some form of abnormal behavior and causing some social impairement.