e symptoms rose threefold from the baseline of 5.11/1000 PYAR in 1996 to 15.5/1000 PYAR in 2006 (online Table DS2). Females had symptoms recorded twice as often as males, which is similar to the findings of recorded diagnoses. Adults in the 25 to 44 age group had the highest rate of depression symptoms, compared with those in the 16 to 24 age group. Those in the most deprived group had depressive symptoms recorded nearly twice as often as the least deprived group.
For recorded depressive symptoms there was an interaction of age with calendar year and age with gender, so the IRRs for year, compared with the baseline of 1996, were stratified by age and gender (Tables 1 and 2). In 1996 the incidence of depressive symptoms in those aged 75 and over was 41% greater than in the 16- to 24-year-olds, whereas in 2006 the incidence was 32% less. There was a lower incidence of recorded depressive symptoms in older age groups (aged 65 years or more) compared with younger age groups in women, but this difference was less marked among men. The effect of gender and deprivation on incidence of symptoms did not change substantially with time.
Combined incidence for diagnoses and symptoms
The results above demonstrate a fall in the recorded incidence of diagnosed depression, but an increase in recorded depressive symptoms, although the combined incidence rates varied little over time (Fig. 1). The combined incidence over the study period was 24.8/1000 PYAR, equivalent to a mean annual incidence of 2.5%. We had categorised depression codes into two lists (diagnoses and symptoms) and included the code ‘depressed’ in the symptoms list. However, this code is commonly used and may be used by GPs as a diagnostic code, so we re-analysed the data with ‘depressed’ as a diagnostic code. This made only a small difference, slightly increasing the incidence of diagnosis, and decreasing the incidence of symptoms, and made no appreciable difference to the IRRs.
Since 1996 the incidence of recorded diagnoses of depression in UK general practice has fallen, whereas the incidence of recorded depressive symptoms has increased. However, the combined overall incidence has remained remarkably stable. The incidence, for both diagnosis and symptoms, was highest in females and those in the most deprived quintiles of the population. This finding was consistent over time. People in the 25- to 44- and 45- to 64-year-old age groups had the highest incidence of both depression diagnoses and depressive symptoms. Recording of depression in older adults seems to have fallen relative to younger groups.
Most primary care research is based on community samples or on GP attendees, with a predominant focus on prevalence. Our study reports on people who had consulted GPs and been identified as having depression or depressive symptoms, and this information had then been entered in the electronic record. We would therefore expect lower incident rates than those observed in epidemiological case-finding studies of community or GP samples. To our knowledge there are few studies that have reported on this population and the GPs’ entry of diagnosis in the electronic records.
The decrease in recorded depression diagnoses in our study contrasts with the increasing prevalence of the disorder in USA epidemiological studies,4,5 although UK community studies6 indicate that the prevalence of ‘neurotic disorders’ has remained stable despite rising antidepressant prescriptions.7,19 Our amalgamated incidence rates of depression diagnoses and symptoms remained stable over the 10-year period, which mirrors similar community prevalence rates recorded in the two waves of the British Survey of Psychiatric Morbidity6 (1993 and 2000).
Our results could be explained by a change in GPs’ recording behaviour, with a reduced entry of depression as a diagnosis and an increased recording of depressive symptoms during this period, rather than a true decrease in the incidence of depression. The move towards recording symptoms and less specific terms may be perceived as less stigmatising for individuals. Gener