- A widely-cited 2007 survey found one in four people in England experienced mental illness at various points in that year. This wasn’t the original source of the 1 in 4 figure, which goes back to the 1980s.
- The finding is regularly misinterpreted as meaning that one in four of us will suffer from a mental illness in our lifetimes.
- The 2007 study measured different conditions in different time frames so the findings can’t tell us how many have suffered from mental illness in any one of these periods.
- Separately, the Health Survey for England found in 2014 that one in four people reported having been diagnosed with at least one mental illness. A further 18% said they’d experienced an illness but hadn’t been diagnosed.
The prevalence of mental illness
“One in four” is widely cited in the UK as the number of people who suffer from a mental health problem.
The estimate has been around since the 1980s, although a commonly cited source for the figure is the more recent Adult Psychiatric Morbidity Survey (APMS). This found that in 2007 23% of people in England had at least one psychiatric disorder at some point in that year, and a third of these—7.2% of people—had more than one.
Because each condition included in the 23% figure has a different time frame it’s not meaningful to use the data to say 23% are ill in every year, or in any other time period. But the findings do suggest that the number suffering over a lifetime will be more than one in four.
The figures are based on whether survey respondents met criteria that indicated certain illnesses and in some cases on follow-up interviews with medical specialists. The methods used vary by condition.
For example, to screen for Posttraumatic stress disorder (PTSD), respondents were asked if they had experienced a traumatic event. If they had, they were asked if they had experienced any of ten symptoms, including jumpiness or difficulty sleeping, twice in the past week. Those who answered yes to six of the ten symptoms screened positive for PTSD.
The findings are broken down by disorder:
These numbers measure the ‘prevalence’ of conditions, meaning they count all those who were ill that year rather than just those who became ill that year.
The next Adult Psychiatric Morbidity Survey will cover 2014 but isn’t due to be published until late 2016.
Lifetime mental illness: uncertain estimates
Because the 2007 survey looked at different disorders relating to different time frames, we can’t attach a time frame to them as a whole.
But the findings do suggest that at least a quarter of people, and probably more, will suffer from one of those illnesses in their lifetime. That’s because of the three-quarters who were not found to have been mentally ill at any point in 2007, some will have previously been ill or will become ill later in life.
The recently published 2014 Health Survey for England also suggests a higher lifetime figure.
It found that 26% of adults reported having ever been diagnosed with at least one mental illness. And a further 18% reported having experienced a mental illness but not having been diagnosed.
That’s based on what diagnoses people report having received, and how they view conditions they’ve had that weren’t diagnosed. There are limitations with this kind of approach because, unlike the APMS, it relies on the perceptions of the people surveyed rather than a systematic attempt at diagnosis by experts.
And, since it’s trying to measure illness experienced across the lifetimes of those surveyed, it’s only as good as the memories of its participants, and in some cases how they self-diagnose their conditions.
There’s some evidence to suggest people can tend to see mental health disorders differently to those designing the surveys. 26% of respondents to a 2013 survey of people in Scotland said they had personally experienced a mental health problem at some point in their life time. The proportion rose to 32% when asked if a health professional had ever diagnosed them with one or more of a list of 15 different mental health disorders. That suggests some people may not have been aware of the types of conditions that fall under the umbrella term of “mental health problems”.
Other evidence on mental health
Research by David Goldberg and Peter Huxley from 1980 found that one in four people in its sample had suffered some sort of mental disorder in a year. It didn’t look at the same conditions as the APMS (so it didn’t include drug or alcohol dependence for example).
More recent data is available on the numbers who are in contact with mental health services.
But this doesn’t tell you how many people are suffering from a mental health problem, as clearly not everyone who is mentally ill will receive a diagnosis or treatment. For many illnesses covered by the APMS, less than a quarter of sufferers were in treatment at the time of taking the survey.