Nearly 6% of Americans suffer from a mental illness doctors barely understand

Pamela Tusiani was 20 years old when she suffered what her mother described as a "sudden and life-shattering nervous breakdown."

As she wrote in an article for Newsday, some days she would be bedridden, unable to eat or speak to anyone; other times she would lash out in anger at people she cared about, or cut herself to feel some relief from her emotional pain.

"My daughter is losing her grip on reality, and I've never been so scared" her mother wrote in "Remnants of a Life on Paper," a book that looks at Tusiani's illness from both her mother's perspective, and Tusiani's perspective, as seen through her diary entries.

"I keep thinking and thinking, it won't stop - so many thoughts are racing through my head. I'm confused, can't remember. I find myself drawn to my bed and cry for no reason at all," Tusiani wrote in her diary. "I don't know what to do, think, or feel. There is so much darkness and sadness, it's almost impossible to see it."

After a series of in- and out-patient hospital stays, Tusiani was diagnosed with borderline personality disorder (BPD), a mental illness that affects an astounding 5.9% of American adults at some point in their lives, according to the National Education Alliance for Borderline Personality Disorder. But despite the prevalence of the condition, BPD is notoriously difficult to diagnose and, subsequently, difficult to treat.

Tusiani herself suffered from a myriad of symptoms that overlap with other mental illnesses like depression, eating disorders, substance abuse, and bipolar disorder. In fact, many sufferers of BPD also suffer from many of these other mental illnesses separately, so it's no wonder that BPD is often misdiagnosed and mistreated.

BPD has been linked to both genetic and environmental factors, like traumatic childhood events. According to the National Institute of Mental Health, BPD wasn't added to the Diagnostic and Statistical Manual for Mental Disorders until 1980, and today experts agree that the name of the illness is misleading, as "borderline" implies that the illness was an atypical version of some other mental illness.

BPD symptoms usually begin in adolescence or early adulthood, and are marked by emotional instability like extreme mood swings and outbursts, impulsive or reckless behavior, unstable relationships, and suicidal thoughts or self-harming behaviors. Some of these symptoms, while not in the extreme, happen to be common among adolescents in general, making it even harder to diagnose. That said, there is no test to diagnose BPD - often it comes down to a process of elimination, ruling out other possible mental illnesses.

Although they may not disappear altogether, symptoms are said to ease as the sufferer ages. Some medications like antidepressants or antipsychotics help some people. But as of right now, there is no medication that treats BPD specifically.

And, as Tusiani's mother describes in "Remnants," some medications can lead to lethal interactions, as was the case with her daughter, whose particular antidepressant caused a fatal cerebral hemorrhage, a burst artery in the brain that kills the brain cells, when she was just 23 years old.

"We only have medications that treat individual symptoms," Columbia University medical professor of psychology in psychiatry Barbara Stanley recently told The Washington Post's Aleszu Bajak at a day-long event for BPD researchers and counselors hosted by the Tusianis this summer. "And [these medications] only give them partial relief."

Psychotherapy, or "talk therapy," has still been proven to be effective, and until more research is conducted on a better treatment, if not a cure, for BPD, the process remains a painful trial-and-error for patients, their families, and their doctors.