The mother of a mentally ill daughter who killed herself last month has revealed how her condition worsened over years and eventually drove her to suicide . Doris Fuller 's daughter , Natalie , 28 , suffered from bipolar disorder and psychosis , and died when she stepped in front of a train in Baltimore , Maryland , last month . And in the wake of her death , Fuller has written about how her illness , which went undiagnosed until her early 20s , and said she was 'the bravest person I have ever known ' . Scroll down for video . Opening up : Doris Fuller 's daughter Natalie , left with her mom , killed herself last month - and now Fuller has opened up about how Natalie 's bipolar disorder and psychosis led to her death . The mother and daughter pair had shot to fame in 2004 when they collaborated on a parenting guide based on Natalie being totally honest with her mother about whatever she was asked . Bestseller : Natalie opened up to her mom - and the result was this popular parenting book . In a long article about her daughter 's life for the Washington Post , Fuller wrote how their famously close relationship was changed for good when Natalie had her first psychotic episode at the age of 22 , after she had left for college . Fuller wrote : 'In the span of a few weeks she went from being a dazzling young adult with the world at her feet to a psych-ward patient with an arrest record . ' Summarizing her last years , she said : 'My daughter lived more than six years with an incurable disease that filled her head with devils that literally hounded her to death , and she did it while laughing , painting , writing poetry , advocating and bringing joy to the people around her . 'She was the bravest person I have ever known , and her suicide doesn ’ t change that . ' And though medicines and proper treatment gave Natalie her life back for a time , she eventually decided to stop taking her meds , which brought her troubles back , even more acute than before . In a mental health documentary video filmed in 2014 , Natalie described the worst lows of her condition , in which she said terrifyingly real voices would tell her to hurt herself . She told the cameras : ' I believed that everything happening to me was real , and I thought that I was acting fine . 'But my mom and my brother and everyone around me could see something that I could n't see . 'Even though [ the voices ] were telling me to hurt myself and do horrible things to myself , I still listened to them because I had a relationship with them . I thought they were real . ' Although Natalie , a keen artist who sculpted , painted and wrote poetry , often seemed fine while on medication , Fuller told how her future seemed a little bleaker every time she relapsed . Difficulties : Natalie ( left in 2014 ) was not diagnosed with a mental health problem until she was 22 - before then she had a regular childhood ( right ) . She told how as she grew older voices started telling her to harm herself . Growing up : As a teenager , Natalie 's no-holds-barred honesty helped make her mom a bestseller . She wrote : 'If she even inadvertently missed a few days of medication - even while receiving therapy and other forms of treatment - the demons would return , and one of the first things they would tell her was to stop taking her medicine . 'The second thing they would tell her was not to talk to her mom , the most powerful other influence in her life . 'Each time she obeyed and relapsed , she plunged into a longer free fall , hitting the ground harder , recovering more slowly and returning at a lower plateau . ' According to the article , the final , ultimately fatal , change came last fall when Natalie concluded that the drugs were not helping her at all , and gave them up for good . Fuller was not specific about what happened in Natalie 's last weeks , though in a post on a tribute site to her daughter , she mentioned that she had holidayed in Nicaragua with members of her family in February . Fuller , the executive director of the Treatment Advocacy Center charity has said since Natalie 's death that she wants her 'legacy ' to be increased understanding and compassion for the those who have mental illnesses . Treatment : When she featured in the video , Natalie told how she was living in a treatment facility and caring for animals in a bid to get better . Missing her : Natalie would have been 29 last week -pictured above is a cake her mother had made for her .
Natalie Fuller , 2004 , stepped in front of a train in Baltimore last month . Mother Doris shared an account of her life this week in heartfelt article . Told how she was diagnosed with psychosis and bipolar disorder aged 22 . Pair wrote bestselling book , Promise You Won ’ t Freak Out , in 28 . Featured nationally on network news and was featured on Oprah .