Parental alienation involves the systematic brainwashing and manipulation of children with the sole purpose of destroying a loving and warm relationship they once shared with a parent.
This means that through verbal and non verbal actions and mannerisms, a child is emotionally abused (brainwashed) into thinking the other parent is the enemy. This ranges from bad mouthing the other parent in front of the children, to withholding visits, to pre-arranging the activities for the children while visiting with the other parent.
Alienated children can experience low self-esteem, self-destructive behaviors, anger, aggression, cruelty, depression, anxiety, post-traumatic stress, and may have suicidal tendencies. (Exerpted from the brochure produced by http://www.parental-alienation-awareness.com/)