Depression in middle-aged women has doubled in 40 years because of the pressures of balancing work and children, a major European study has found.
Women are more than two-and-a-half times more likely than men to suffer from depression, with most cases occurring during the "reproductive years" between the ages of 16 and 42.
The burden of trying to look after children, take responsibility for the family and hold down a job has seen rates of depression in women double since the 1970s, experts said.
Both men and women are now suffering from depression earlier than before, with the first symptoms arriving at the average age of 19, compared with 26 four decades ago.
But the "tremendous burden" of trying to juggle home and family life means that between the ages of 25 and 40 women are three to four times more likely to become depressed than men.
Professor Hans Ulrich Wittchen, one of the lead authors from the Dresden University of Technology in Germany, said men and women were equally prone to mental health problems but that some disorders affected one sex more than the other.
He said: "Marriage appears to reduce the risk of depression in males, for females it increases the risk."
"In females, you see these incredibly high rates of depressive episodes at times when they sometimes have their babies, where they raise children, where they have to cope with the double responsibility of job and family."
The study of 30 European countries including Britain, published by the European College of Neuropsychopharmacology, found that 164.8 million people – or 38.2pc of the population – suffers from a mental disorder.
All major mental health disorders were included, including depression, bipolar disorders, anxiety disorders, insomnia, addiction and schizophrenia.
The rate is significantly higher than the 27pc estimated in a 2005 study, but the increase was down to more disorders being assessed rather than a rise in the overall number of sufferers, Prof Wittchen said.
The most common issues included anxiety disorders, which affected 14pc of the EU population last year, insomnia (seven per cent) and major depression (6.9pc).
The 2005 study estimated the total cost of mental disorders within the EU at €276.8bn a year, and financial estimates from the new report, to be published next month, will be "considerably" higher, Prof Wittchen said.
Diagnosing these conditions early is important, he added, because they place a greater burden on society than any other disease group.
Prof Wittchen said: "Disorders of the brain are not costly and burdensome because the treatment is challenging.
"It is because of the indirect cost – people are getting no treatment and the progression of the untreated disorders goes on until it is so complicated that the disabilities accumulate, and that is responsible for the burden."
There is increasing evidence that the clearest marker for the risk of diseases like Alzheimer's and Parkinson's disease is late-onset anxiety disorders that arrive in middle age, Prof Wittchen added.
The onset of symptoms like panic attacks and difficulty getting to sleep can predate a diagnosis of Parkinson's disease by five to six years, he said.