Young adults working in zero-hours jobs could be suffering a significant impact on their mental and physical health, a new study suggests.
A major survey of millennials found that those on the insecure contracts in which there are no guaranteed minimum hours were at much higher risk than those with stable jobs.
Researchers found that people in zero-hours roles were 50% more likely to report they suffered from mental health problems, according to the study of 7,700 people born in 1989-90 and living in England.
They were also 41% less likely to suffer good health as a whole than people not on such contracts, said the Centre for Longitudinal Studies at the UCL Institute of Education.
Dr Morag Henderson, the lead author of the study, said worries over financial uncertainty could be among the causes of poor mental health for those in the positions.
That could cause physical symptoms including including chest pain, headaches and muscle tension, she said.
The number of people on zero-hours contracts in the UK has risen sharply in recent years to over 900,000 workers nationally.
On average, they are more likely to be young, part-time, women, or in full-time education and work on average for 25 hours a week, according to latest data from the Government.
The highest proportion worked in education, followed by the hospitality sector and then administration and support roles.
The contracts have been criticised for leaving people without security or normal employment rights in what critics say is abuse of workers.
Commenting on the study, TUC general secretary Frances O'Grady said it was no surprise to see a link between the contract and poor health.
"If you don't know how much work you will have from one day to the next, this is bound to impact on your health and mental well-being," she said.
"Employers must not be allowed to get away with treating workers like disposable labour."
The Government has responded to concerns by commissioning a review into the contracts carried out by former Downing Street advisor Matthew Taylor.
A spokeswoman from the Department of Business, Energy and Industrial Strategy said: "We are committed to building an economy that works for everyone and making sure employment rules and rights keep up to date to reflect new ways of working."
She added that Mr Taylor had been looking at work and well-being in his review, which should be published shortly.