(CNN) -- Tara grew up thinking that spankings or a smack on the arm were normal punishments for breaking a plate or playing her music too loudly. She never knew what would set her father off, and her mother never intervened, so she did her best to avoid him, walking on eggshells whenever he was around.
"It wasn't until I grew older and was out from under my parents' roof that I learned it wasn't the norm," said Tara, a 34-year-old public relations consultant in Phoenix. She asked that her last name not be used because she no longer talks to her father and fears drawing his attention.
"I think my father truly didn't care enough to 'teach' me how to be, but instead would try to knock undesirable behaviors out of me."
As she watched the YouTube video last week of a Texas judge beating his daughter, Tara's mind wandered to an afternoon in her senior year of high school more than a decade ago, when her father's idea of discipline turned into violence.
He burst into her room, yelling and swearing. Another teacher at Tara's East Tennessee high school, where her father worked, had told him that students were saying that she had kissed a black boy. He cursed at his daughter as he slapped and punched her all over, his clunky school ring pounding her skin like a brass knuckle.
"Seeing that girl made me think, wow, that's what I lived through," Tara said. "I saw so much of myself in it, it made me shudder to think back on it."
Among psychologists, Tara's flashback is considered a symptom of post-traumatic stress disorder from years of physical and emotional abuse, and it's just one of many potential lasting effects when discipline crosses the line into abuse.
Parents have long been using spankings, swattings or whippings to "correct" a child's behavior. But as social norms evolve and more research surfaces in support of alternatives, the line between "corporal punishment" and child abuse is becoming increasingly blurry.
The controversy came to the fore last week, when the YouTube video of the judge repeatedly hitting his teen daughter went viral. The video is a stark depiction of a wailing girl in a dark room begging her father to stop whipping her with a belt, and it prompted widespread outrage.
The daughter, now 23, said she posted the video to make a point to her father, who she felt was in denial about the way he treated her years ago. William Adams, a court-at-law judge in Aransas County, Texas, faces a judicial conduct investigation because of the incident. He will not face criminal charges because the statute of limitations on a charge of felony injury to a child has expired.
Spankings under the guise of discipline are still commonplace in the United States. A fair share of reaction to the YouTube video contained the sentiment that physical discipline reinforces the notion of consequences for actions.
"Parents waste a lot of words on kids. Kids want what they want. A lot of times, a good spank to the bottom communicates the words that you have to communicate," said Chad Smith, a personal trainer from Hagerstown, Maryland, whose mother took a belt to him whenever he got out of line.
"That being said, there's a difference between discipline and abuse. People tend to think of abuse when they think of manual correction, but there's a line there. With that video, what got to me was her age, and the fact it went on for so long."
For Tara, who endured prolonged or severe instances of violence under the guise of discipline, the video took her breath away. It also forced her to reflect upon how her experiences with "physical correction" had altered the course of her life.
"I suffer from anxiety and never really feel 'safe.' I worry a lot about the most trivial things, and I truly believe this is a result of me never feeling safe in my own home," she said. "Luckily, I have a good therapist and an amazing husband who doesn't have the same baggage as me."
She is lucky, because she, and many like her, might seek the familiarity of an emotionally volatile relationship or subject their own children to similar treatment.
She grappled with the prospect of having children, fearing that she might treat them the same way her father treated her.
"I can't say I never gave them a pop on the bottom in the beginning, but never to the same extent as my dad," she said. "Counseling has helped me understand that when I get mad with them, it's up to me to stop and really think and put things in perspective. Most of the time, it's based on things going on in my world that stress me out."
Just as crucial to seeking treatment was learning to forgive her parents -- still a work in progress, she said. It's not about excusing or absolving them of what they did, but understanding what motivated the behavior and empathizing.
"He was beaten as a child as well, and I am sure this kind of behavior with his own children was a learned behavior, but through education and understanding, I just can't imagine that an adult couldn't make better decisions to change and make the lives of their own children better by doing the hard work to improve their own parenting shortcomings. "
Numerous studies have been conducted in recent years to support the theory that physical forms of discipline do more harm than good, said George Holden, a professor of psychology at Southern Methodist University, who has published five books on parenting and child development.
"The line between discipline and abuse is a gray area, and it's also sort of fluid because a parent might begin with using what they consider appropriate or reasonable discipline. But in the course of seconds, it can easily escalate based on a child's reaction or a parent's rage," he said. "It's easy to inadvertently cross the line, wherever it is."
Hurting your child can also harm the parent-child relationship by infusing it with pain and negative emotions, he said. Children who are spanked are also more likely to be aggressive toward others because they don't know any other way to behave.
When physical force is combined with derogatory or emotionally abusive comments, like the ones in the YouTube video, the damage can be even greater, said psychologist Gregory Jantz, author of "When Your Teenager Becomes the Stranger in Your House."
"You're degrading their personhood, attacking them as a person, their character, their worth and value," he said. "Combine that with the anger and the hitting, that's what we call violence, and that's about power and control: one person, through physical force, exerting power and control over the other."
Studies have also found an elevated risk of heart disease related to childhood trauma, said psychologist Melanie Greenberg, who studies the effects of stress and trauma on the mind and body.
"There is evidence that child abuse changes brain function in areas related to processing threat. Chronic stress can lead to imbalance of the autonomic nervous system," she said, referencing the Adverse Childhood Experiences Study, a collaboration between the Centers for Disease Control and Prevention and Kaiser Permanente.
Such an imbalance can distort one's fight-or-flight perception, causing a tendency to overreact or magnify perceived threats, she said.
Denise Parker knows it firsthand. She recalls the time she bought a bottle of wine with a pretty label for a former boyfriend that turned out to taste awful. She was immediately paralyzed with fear, expecting that he might yell at her or break up with her.
Years of counseling helped her realize that it was her father's voice in her head, telling her that she was stupid and not good enough, just like he had when she was younger.
"He thought it was discipline. It could be that we did something wrong, we spilled something or broke a dish, but to me, the punishment never matched what happened," she said. "I think all the anger he had inside would come out in those moments. Anything could be under his guise of needing to punish us for something."
Other patterns have been harder to break, she said. Her husband, who was beaten as a child, was verbally abusive until a few years ago, when she started to go to counseling and learned to assert herself.
"I was attracted to the unfinished business with my dad, the level of comfort with someone who also had so many issues, because I knew how to manage them," she said. "I believed if he loved me enough, he would go to counseling and be willing to change.
He never did, though, she said. She and her husband have a daughter and a decent life, but she doesn't see it lasting forever, she said.
"His behavior is nothing like my dad's, there's no abuse and he doesn't hit her, but he doesn't give her enough attention," she said. "I try to manage that relationship best way I can by creating a life for her that's very different from the childhood I had."
Keeping anger out of the situation is the key to effectively disciplining a child, said clinical psychologist Marla Deibler, who performs court-ordered evaluations for children and families in New Jersey's family court system.
"You punish kids because you don't want them to do it again, but physical force doesn't show them what to do instead, and it doesn't educate them on a better way to cope or problem solve," she said. "It's crucial that they understand why they're being punished and that the punishment is reinforced with positive emotions."
Jonathan Holliday agrees that it's all in the approach. He credits his childhood whippings with teaching him the difference between right and wrong and instilling in him respect for his parents.
"After I'd get a spanking, I would think the next time before I did something," the 21-year-old University of Arkansas student said.
His mother disciplined her son and daughter, he said. She always explained to them what they had done to prompt her use of the belt, he said. When the whippings were over, she would leave the room for a bit and return to give them a hug and reiterate the lesson she wanted them to learn, he said.
"The main thing is she never whooped us without reason and she always backed it up with love," he said. "I could tell she hated doing it, but she never did it out of anger. She did it out of love and the fact she was worried about our actions. She didn't do it because she was angry, and she never cursed and she always had an explanation for it."