NEW YORK – On the surface, it appeared as though Ms Antoinette Del Rio was a successful 20-something. She had a flourishing career in advertising, took frequent vacations and enjoyed an active social life.

But Ms Del Rio was drinking too much, using weed as a coping mechanism and spending weekends holed up in her New York City apartment. She had also fallen into debt from impulsive overspending and frequently fought with her friends.

Soon, she began to notice a troubling pattern in all of her relationships: They felt either euphoric or devastating, with no middle ground.

A seemingly small conflict could cause her to completely lash out without thinking of the consequences, said Ms Del Rio, now 33. Sometimes, she was so angry that she would pull out her hair or dig her nails into her skin “as hard as possible”.

In 2022, her primary care doctor pieced it all together. Ms Del Rio was showing telltale symptoms of borderline personality disorder, or BPD, a condition characterised by volatile relationships and emotions, alongside reckless behaviour and an empty sense of self.

BPD is challenging to effectively treat, which can “scare the pants off therapists”, said Dr Lois W. Choi-Kain, director of the Gunderson Personality Disorders Institute at McLean Hospital in Belmont, Massachusetts.

But people can – and do – get better, she added, even those with more issues like substance use and disordered eating.

Dr Choi-Kain said she had seen people who were very ill develop the skills to feel good about themselves, and then be able to manage a relationship differently.

Mental health practitioners define borderline personality disorder as a pattern of instability in someone’s relationships, self-image and emotions.

People with BPD have a tendency to do things without thinking, sometimes engaging in activities such as reckless sex, substance abuse or self-harm, which is often what leads them to treatment.