What happens when one parent poisons a child against the other parent

Article here. Excerpt:

'Parental alienation is a controversial topic and still the subject of much debate in both the legal and medical communities. Some psychologists view the condition to be similar to Stockholm’s Syndrome, commonly known as brainwashing, in which captives become sympathetic with their captors in their innate drive to survive.
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The psychological underpinnings of “alienators” are complex and confusing. Craig Childress, a leading authority on PA who practices in Pasadena, says parents who use brainwashing tactics on their children to fulfill their own selfish need to harm or denigrate an ex-spouse most often fit the profile of a person with Narcissistic Personality Disorder or Borderline Personality Disorder. People diagnosed with personality disorders are difficult to treat, and oftentimes will never even be diagnosed.
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The outcome of such mind games pushes the child to cut the targeted parent out of their life, and the unthinkable occurs: The child’s relationship with either mother or father comes to an end.
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He said parental alienation “is not a child custody issue, but a child protection issue. Psychopathology is induced in the child to meet the parents’ (or step-parent’s) emotional needs. It’s a very destructive parent/child relationship.”

Social services will not intervene even if a diagnosis of PA is made. “If you get a clinical diagnosis it should happen, but it doesn’t,” he said.'