Nearly a fifth of all people in the UK experience anxiety or depression, according to figures.
The Office for National Statistics (ONS) said that a higher proportion of women than men reported that they suffered from the conditions, with the highest indication of anxiety or depression occurring in the 50-54 age group.
There was evidence of anxiety or depression in a total of 19% of people aged 16 or over, with 21% of women reporting the symptoms and 16% of men.
People who were divorced or separated were more likely to have symptoms of mild-to-moderate mental ill health, with 27% showing signs of the conditions compared with 20% of those who were single, cohabiting or widowed and 16% of those who were married or in a civil partnership.
Higher levels were also recorded by those who were not in paid work, with 23% reported they were experiencing mental health issues, compared with 15% of those who were in paid work.
The ONS also revealed that 38% of those who said they were relatively unhappy with their health had some indication of anxiety or depression, compared with 11% of those who declared themselves to be relatively satisfied with their health.
Carers were more likely to report mild to moderate mental health issues, at a rate of 25% of those questioned, compared with 17% of people who did not provide such care.
The study is part of the ONS Measuring National Wellbeing Programme which saw people in 40,000 households surveyed between 2010 and 2011. The figures come from the general health questionnaire, in which they were asked 12 questions about their levels of self-confidence, stress, depression and self-worth.
The ONS said the types of mental illness recorded on the questionnaire did not include severe mental disorders.
The latest figures released as part of the wellbeing study also showed that 66% of people in the UK are satisfied with their health. In those aged 80 or over, satisfaction with health fell to 53%.
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