There were more than 1,300 cases where people were readmitted to mental health hospitals within 28 days of being discharged last year, figures have shown.
Exactly 1,331 cases fell into that category - almost one tenth of the total number of mental health discharges in 2011.
The Scottish Government statistics were obtained by the Scottish Liberal Democrats, who called for action from ministers to tackle the issue.
Party leader Willie Rennie MSP said: "This cycle of readmissions is damaging for the well-being of mental health patients and their families and puts further pressure on the NHS."
The figures were provided by Health Secretary Nicola Sturgeon in answer to a written question from Alison McInnes MSP, the Scottish Lib Dems' spokeswoman on health.
They revealed that there were 14,647 discharges from mental health hospitals in Scotland in 2011. Of that figure, 1,331 - just over nine percent - were subsequently readmitted within a month.
In percentage terms, Dumfries and Galloway NHS board had the highest readmission rate at 14%. Grampian and Lanarkshire were next at around 10% each.
The Scottish Lib Dems said the figures underlined the need for the Scottish Government to focus on effective community care for mental health patients once they leave hospital.
"Nearly 10% of all mental health patients were readmitted within 28 days after discharge. This must be tackled," Mr Rennie said.
"When it comes to mental health, there is no quick fix. Those with mental health problems need to be cared for in the way that suits their needs best.
"This is why the Scottish Government must make sure that sufficient support is available in the community they are being discharged to. This includes support for the individual, their families and carers.
"Whilst some patients may have to be readmitted for their own well-being, readmission due to lack of support in the community is preventable.
"The Scottish Government must promote tailored community mental health care in their upcoming Mental Health Strategy."