Cost of hospital contacts

The number of hospitalisations for depressive disorder and recurrent depressive disorder was taken from Hospital Episode Statistics (Department of Health, 2000a ). Two ICD–10 (World Health Organization, 1992) diagnosis codes were applicable: F32 (depressive episode) and F33 (recurrent depressive disorder). The total numbers of day cases, defined as treatment during the course of the day that does not require an overnight stay (Department of Health, 2000a ), for depressive disorder and recurrent depressive disorder were reported in Hospital Episode Statistics. The cost of admissions and day cases was then calculated by multiplying the number of admissions and day cases by the mean average cost per admission and day case given in Healthcare Resource Group data (P18, psychiatric disorders), from the national schedule of reference costs (Department of Health, 2000c ).

Out-patient consultations

Out-patient consultation data were available by sector and specialty from Consultant Outpatient Attendances by Sector (Department of Health, 2001), but there was no specific figure for consultations for depression. Therefore the number of in-patient episodes due to depression as a proportion of all mental health episodes was calculated (16%) and this percentage was applied to the total number of mental health out-patient attendances. This is likely to be an underestimation in view of the finding that only 5% of depression is treated in the hospital setting (Reference Jönsson and BebbingtonJönsson & Bebbington, 1994). (For comparison, an earlier study estimated that affective disorders contributed 21% of the total cost of mental illness in the USA in 1990 (Reference Rice and MillerRice & Miller, 1995).) Data from Key Health Statistics from General Practice (Office for National Statistics, 1998) were also examined to identify a more accurate estimate of out-patient consultations. However, in this source out-patient referral rates were only available for psychiatry as a whole rather than specific to depression; these data therefore were subject to the same limitations and would not be as recent as the published figures that were used. The cost of depression-specific out-patient consultations was then calculated from Reference Costs 2000 (Department of Health, 2000c ) on the basis of specialty code 710 (mental illness).

General practice consultations

Rates of general practitioner consultations by patients with depression (ICD–9 classifications 298, 300.4 and 311; World Health Organization, 1978) were obtained from Morbidity Statistics from General Practice (Office for National Statistics, 1995). These rates were applied to the 2000 population data and the cost calculated using unit costs of health and social care (Reference Netten and CurtisNetten & Curtis, 2000).

Drug consumption

Prescription cost analysis data (Department of Health, 2000b ) give the number of prescriptions and net ingredient cost per prescription of antidepressant drugs prescribed, categorised by antidepressant class. Key Health Statistics from General Practice (Office for National Statistics, 1998) gives the proportion of drugs in each anti-depressant class prescribed for patients with treated depression, analysed by age and gender. The cost of antidepressant medication was then calculated using the net ingredient cost per script as given in the prescription cost analysis data.

Indirect costs

Indirect costs of depression arise when people with this disorder are unable to function as a result of their illness (Reference Kind and SorensonKind & Sorenson, 1993), manifested by the inability to work (morbidity costs). Furthermore, a proportion of people with depression die from suicide or accidental poisoning that is related to the diagnosis of depression (mortality costs).

Prevalence of depression

There were estimated to be 2.6 million cases of depression in England in 2000 (Table 1). In 72% of cases the patient was female, and 20% of cases occurred in the 35–44 years age band.

Table 1 Prevalence of depression in England in 2000

Age (years)	Cases per 1000 patients1		Number of cases		Total2
	Male	Female	Male	Female
16—24	15.6	45.2	48 156	131 939	180 094
25—34	31.5	87.1	121 555	317 654	439 209
35—44	40.3	102.7	154 829	381 387	536 215
45—54	48.0	108.9	157 555	357 649	515 205
55—64	48.5	102.8	122 458	265 964	388 422
65—74	40.1	98.6	76 635	214 632	291 268
75—84	49.8	104.9	53 510	172 477	225 987
85+	56.5	96.5	15 261	69 808	85 069
Total2	29	70.1	749 958	1 911 510	2 661 468

Direct costs

The components of the direct costs of treating depression that are borne by the National Health Service (NHS) are estimated to be £369 865 000 (Table 2). These comprise in-patient, day and out-patient care, general practitioner consultations and medication. The cost of each component and its respective proportion of the total direct cost is also indicated.

Table 2 Components of the direct National Health Service treatment cost of depression

Direct costs	£ ('000)	%
In-patient care	28 660	7.7
Day case	476	0.1
Out-patient care	22 133	6.0
General practitioner consultations	8217	2.2
Antidepressant medication	310 378	84
Total	369 865	100

Morbidity costs

Claims for incapacity benefit for people in England with a diagnosis of depression (F32 and F33) indicate that 109.7 million working days were lost as a result of depression. The total of lost earnings is estimated at over £ 8 billion. Table 3 lists the number of working days lost by men and women in various age groups; almost a fifth of the days were lost by women aged 35–44 years, who have the highest prevalence of depression.

Table 3 Working days lost owing to depression in 1999—2000

	Days lost ('000)
Age range (years)	Men	Women	Total
15—24	2590	7109	9699
25—34	6416	16 843	23 259
35—44	8205	20 354	28 559
45—54	8372	19 061	27 433
55—64	6535	14 283	20 818
Total	32 118	77 650	109 768

Mortality costs

There were 3583 suicides in the year studied, and 2507 of these are estimated to be related to depression. Suicides in people with depression were most frequent in men aged 25–34 years. In the same year there were also 1058 deaths due to accidental poisoning with drugs, medicaments and biologicals, an estimated 108 of which were due to poisoning with antidepressants. The total number of deaths in England in 2000 estimated to be associated with depression is 2615 (Table 4). To estimate the loss of future lifetime earnings arising from premature death related to depression, the number of deaths was multiplied by discounted life expectancy data, resulting in a loss of an estimated £ 562 million.

Table 4 Deaths associated with depression

	Deaths (n)
Age range (years)	Men	Women	Total
15—24	213	65	278
25—34	471	107	578
35—44	451	120	571
45—54	348	116	464
55—64	209	85	294
65—74	148	66	214
75+	138	78	216
Total	1978	637	2615

Total costs

The total cost of depression in England among adults over 15 years old in 2000 is estimated at over £9 billion. Table 5 presents the direct and indirect cost components compared with estimates from previous studies.

Table 5 Total costs of depression in 2000 compared with two earlier studies

		Kind & Sorenson (Reference Kind and Sorenson1993)	Jönsson & Bebbington (Reference Jönsson and Bebbington1994)
Cost year	2000	1990—1991	1990
Primary care costs (£000)
GP consultations/visits	8217	126 399	NS
CPN		16 285	NS
Medication	310 378	47 280	41 722
Secondary care costs (£000)
In-patient	28 660	177 365	NS
Day-case	477	—	NS
Out-patient	22 133	9146	NS
Social care costs (£000)		40 183
Morbidity cost (£000)	8 123 258	2 973 000
Mortality cost (£000)1	562 151
Total cost (£000)	9 055 274	3 389 658	222 000

Indirect costs

Indirect costs represent the value of lost production to society. Average earnings rates used to calculate the indirect costs may not be an accurate reflection of the wages of people with depression, who may be below-average earners. In this study we use the human capital approach, which is defined as lost income during the time that the patient is absent from work because of sickness, and the lost future gross income due to premature death (Reference LiljasLiljas, 1998). Criticisms of the human capital approach are that it discriminates against those who are not in employment, such as elderly people. In this analysis no cost is calculated for morbidity and mortality in men over 65 years old or women over 60 years old. Furthermore, in reality when people are absent from work, colleagues may cover their work in the short term and in the long term a replacement worker may be appointed. However, the inability to work does represent a societal and personal burden to those who are affected. Our study derived the number of lost days from incapacity claims that were classified by a diagnostic code for depression. Therefore, the number of days lost is a fair representation of this burden, although the cost estimates may not be. Claims for benefits may be an underestimation of the actual number of working days lost, as employers make claims for sickness benefit only after an employee has been absent for 5 days.

Deaths due to depression

The lifetime risk of suicide among people with depression has been estimated at 6% (Reference Inskip, Harris and BarracloughInskip et al, 1998). It is widely assumed that early and accurate identification of depressive disorders will reduce the risk of suicide, and one of the targets set in the recent National Service Framework for Mental Health (Department of Health, 1999) is to reduce the number of suicides. Our study assumes that only 70% of suicides were due to depression. However, it could be argued that all people who die by suicide are suffering from depression. Furthermore, mortality data are likely to be an underestimate, because in a number of reported suicides it is not determined whether death was accidentally or purposely inflicted; these deaths are not included in the analysis but may also be due to an underlying diagnosis of depression. Suicide figures may also suffer from a bias in recording in order to avoid inflicting further suffering on the surviving family (Reference Kind and SorensonKind & Sorenson, 1993).

Deaths due to accidental poisonings were assumed to be related to depression only if they were caused by an antidepressant; however, people with depression may overdose inadvertently on other substances, such as paracetamol. Conversely, it could be argued that not all accidental poisonings with antidepressants occur in people with depression – for example, a family member might take the wrong medication in error. We also recognise that people suffering from depression have an increased risk of mortality from other related conditions, and therefore the number of deaths associated with depression is likely to be an underestimate. Despite these limitations, the number of deaths related to depression is an important indication of the human loss due to unsuccessful recognition of illness or failure of treatment.

Interpretation of the findings

This study estimates that the total direct cost of depression in England is almost £370 million. Previously published estimates of the cost of depression were £222 million in the UK (Reference Jönsson and BebbingtonJönsson & Bebbington, 1994) and £416 million in England and Wales (Reference Kind and SorensonKind & Sorenson, 1993). However, the contribution of hospital admissions in the latter study was almost 40% and this was generated mainly from admissions to specialised mental institutions rather than to general hospitals. The changes in patterns of care and the closure of many such institutions reflect the shift found in our study for the highest contributor to costs to be antidepressant medication rather than hospital care. Conversely, in Kind & Sorenson's study the medication component represented only 11.3% of the total direct costs, which also reflects the greater usage of the cheaper tricyclic antidepressants.

Morbidity costs are nine-tenths of the overall total cost of depression in our study. This is in keeping with the clinical course of depression, which is a chronic and relapsing condition that can successfully respond to treatment. Unfortunately, as patients comply poorly with medication – some studies suggest up to 50% (Reference HaleHale, 1997) – this may lead to a greater chance of relapse and recurrence. We estimated the morbidity costs to be £8.1 billion, which is almost three times the cost estimated by Kind & Sorenson (Reference Kind and Sorenson1993). This may be explained by two factors. First, in the earlier study morbidity costs were estimated on the basis of assumed disease severity and absence from work; in our study, these costs were estimated according to reported incapacity benefit claims, which are likely to be more accurate. Second, average wages have increased over the past decade, and our estimates of labour market participation are higher than those used by Kind & Sorenson.

The ratio of indirect to direct costs in our study is 23, whereas previous studies reported a 7-fold difference (Reference Kind and SorensonKind & Sorenson, 1993). This difference may be largely due to the differences in methodology, along with greater recognition and awareness of depression by patients and clinicians. Although the number of life-years lost was estimated in the Kind & Sorenson study, mortality costs were not calculated. We estimated these to be £562 million in our study, which also results in an overall increase in indirect costs. The cost estimates calculated in our study are based on the most recent national health care resource data available for England. Furthermore, the calculation of both the direct and indirect costs of depression are revisions of those provided in previous studies and incorporate more accurate estimates of resource use by people with depression. Given the number of limitations that remain when performing any cost-of-illness study, the costs we calculated are likely to be an underestimate rather than an overestimate of the burden of depression.

In summary, the cost of depression in England represents a substantial burden on both society and the individual despite improved recognition and awareness, and the availability of effective and accessible treatments. The total cost of managing depression in adults in England in 2000 is estimated at over £9 billion, including almost £370 million of direct treatment costs. These results provide a more accurate estimate of current costs and reflect the shifts in patterns of care and the availability of more accurate health care resource data. The contribution of the cost of antidepressant medication to the direct treatment costs is substantial and provides evidence of the wider recognition and better management of the disease. However, anti-depressant medication costs are a minor proportion of the overall cost of depression. There is a substantial indirect burden associated with depression: in 2000 there were 109.7 million working days lost as a result of depression, and 2615 deaths. The intangible elements of pain and suffering of people with depressive disorders and their families and the effects on quality of life cannot be quantified in monetary terms.

The accuracy of cost estimates is always subject to the limitations of the available data. However, using a ‘top-down’ approach gives an estimation of the actual costs that were allocated in a given year to treating a disease at the population rather than the patient level. The use of mean costs can provide the decision-maker with the average amount that a patient might incur but does not give an indication of the likelihood of that cost occurring. Although population-based cost estimates are incomplete, knowledge of how costs are allocated is important given the excess demand for scarce health care resources. Finally, the contribution of the different components to the overall cost of depression may provide an indication of where strategies to reduce the consequences of disease have the potential to offset significant costs that could be more efficiently allocated elsewhere in society.

CLINICAL IMPLICATIONS

1. ▪ The cost of depression in the UK remains high despite availability of effective treatment.

2. ▪ Morbidity costs comprise 90% of the total costs, illustrating individuals' incapacity to work.

3. ▪ Drug treatment represents a minor proportion of the overall cost of depression.

LIMITATIONS

1. ▪ Data are drawn from a variety of sources, which do not use uniform reporting mechanisms.

2. ▪ There is a lack of depression-specific data for certain components.

3. ▪ Caution should be used when interpreting the mortality/morbidity costs.