The findings of an investigation into the Scottish case found the assessment process "flawed" and "unreliable".
In the document, published today, the head of Scotland's mental health watchdog has said the Department for Work and Pensions (DWP) system needs to be changed.
Dr Donald Lyons, chief executive of the Mental Welfare Commission for Scotland, added that the woman's case also indicated a lack of appreciation of the effects the tests had on vulnerable people's lives.
He said: "I don't think there is enough understanding of the momentous impact these assessments can have. There was nothing else going on in this woman's life that we could identify as to why she took her own life. She was engaged, she was looking forward to getting married. The only thing going on was the benefit assessment.
"I think the DWP should reflect on this case and learn from it. It does suggest that, certainly with regard to people with mental health problems, the assessment process is flawed and unreliable."
The report will put further pressure on Prime Minister David Cameron to review the assessment process which has been criticised for dealing harshly with the sick and disabled.
The commission's report said the former office worker and mother-of-one, referred to as Ms DE, lived in Scotland and was in her early 50s. She had suffered from depression for 20 years and was under the care of a consultant psychiatrist and a GP.
She was a regular churchgoer and had worked for most of her life but had given up her job a few years earlier when her illness deteriorated.
Despite her condition, she had no history of self-harm and had not previously tried to commit suicide.
She was found dead on Hogmanay 2011 after taking an overdose, fearing she would be unable to pay her mortgage because of a substantial drop in income following changes to her benefits.
The DWP's Work Capability Assessment (WCA) - the test carried out to see if someone is fit to work - found she was able to return to work and she was told she would move from £94.25 a week incapacity benefit to £67.50 jobseeker's allowance.
The face-to-face interview was carried out by the outsourcing company Atos Healthcare, which has been at the centre of criticism over the tests.
Ms DE's best friend and doctors told the inquiry she had been highly distressed and was plunged into crisis when she received the letter informing her of the change.
Under the assessment process, Atos was not required to seek further information from the woman's GP or consultant - neither of whom believed she was well enough to return to work.
Dr Lyons said: "One of the most concerning aspects in the case was that the only information the decision maker had to go on was the Work Capability Assessment and everything we found in this case points to this not being a reliable indication of someone's ability to work.
"In this case there was no report from the patient herself, no letters from her GP or her psychiatrist."
Politicians said that the case demonstrated the Work Capability Assessment should be scrapped and a fairer system be introduced.
Labour MSP Jackie Baillie, shadow social justice minister, said: "This case is heart-wrenching. It shows just how broken the benefits assessment system is under Tory reforms. It is imperative the Tory/LibDem Government scraps these changes and ensure any replacement treats people with disabilities with dignity and respect."
A DWP spokeswoman said all procedures and safeguards in Ms DE's case were correctly followed, adding: "This was a tragic case and our thoughts go out to the family. We conducted an internal investigation which found our procedures of the time were correctly followed and the relevant safeguards implemented.
"This report is narrowly focused using a single case from 2011 to make conclusions about the WCA process without taking into account the significant improvements we have made - and continue to make - for people with mental health conditions."
She added the department worked with the commission throughout the review and was committed to improving its processes.
A spokeswoman for Atos Healthcare said it understood that applying for benefit could be a difficult time, and that it was working to make the process as comfortable as possible. She added: "In line with guidance from DWP so as not to overload the GP community we will request further medical evidence only where this is likely to mean that a person will be eligible for benefit without the need for a face-to-face assessment. We do this in about one-third of all cases."