Almost one-fifth of MPs have suffered mental health problems at some time, a survey suggests.
The All-Party Parliamentary Group on Mental Health also found 86% thought being an MP was stressful. Ninety-four MPs took part in the survey.
The group's report criticises the law forcing MPs to give up their seats for life if they are sectioned for six months under the Mental Health Act.
Joint chairman Sandra Gidley said work on "challenging stigma" was needed.
One in three of the MPs said colleagues' attitudes and the possibility of a hostile media reaction prevented openness about mental health issues.
If an MP is physically incapable of working for six months they do not have to stand down, whereas those sectioned for the same period do.
Ms Gidley, a Liberal Democrat MP, said: "Greater openness at Westminster about mental health problems would have a significant impact in challenging stigma and discrimination.
[MPs] are being gagged by the prejudice, ignorance and fear surrounding mental illness
Paul Jenkins, Rethink
"When the former Norwegian prime minister Kjell Magne Bondevik publicly disclosed his experience of depression, it did not affect his popularity.
"He went on to be re-elected and proved that people who have experienced mental health problems can recover and manage a challenging job."
Marjorie Wallace, of the mental health charity Sane, said: "It is extraordinary that even the most vocal people who represent the public still feel unable to discuss their own experiences of stress, depression and other mental health problems.
"It is time that we break the taboos and make mental illness as acceptable to employers and the general public as physical health conditions."
Paul Farmer, chief executive of the charity Mind, said that at a time when the government was appealing to employers to be more understanding about mental health issues in order to help people off benefits, it should be looking closer to home.
"Repealing antiquated rules that ban MPs from returning to work after recovering from a mental health problem would send out a clear message to all employers that discrimination should not be tolerated," Mr Farmer said.
The charity Rethink's chief executive, Paul Jenkins, said: "These findings are an affront to democracy. MPs and peers need to be free to bring their personal experiences to their vital democratic role.
"Instead they are being gagged by the prejudice, ignorance and fear surrounding mental illness.
"We look forward to the day when MPs from all political parties with experience of mental illness are able to participate fully in our democracy."