Screening for Depression in Primary Care

Depression is set to be second only to cardiovascular disease in terms of the world's disabling diseases by the year 2020.¹
Major depressive disorder is associated with a high degree of personal disability, multiple morbidity, suicide and lost quality of life for patients, families and carers. Patients with chronic depression may also be high service users with significant economic implications.²

Depression may not always be recognised by GP's whilst treating a patient's other chronic illnesses, and so practices pursuing the Quality and Outcomes Framework of the GP contract are required to screen patients with coronary heart disease (CHD) and diabetes for depression (Quality Indicator DEP1).³ In patients with a new diagnosis of depression, practices are also required to assess severity within 28 days of the initial diagnosis using an assessment tool validated for use in primary care (Quality Indicator DEP2). A third indicator was introduced in 2009; for patients who had an assessment under the DEP2, a further assessment is required 5–12 weeks later.⁴

The point prevalence of depression amongst 16 to 65 year olds in the UK as 17 per 1,000 for males and 25 per 1,000 for females.⁵ When anxiety and depression are mixed, the prevalence rises to 71 and 124 per 1,000 in males and females respectively.

High-risk groups with prevalence per 1,000 are separated males at 111, separated females at 56, widowed males at 70 and divorced females at 46. The lowest groups are married men and women at 17 and 14 respectively. Unemployment increases the rate to 27 for men but 56 for women. Rates in the homeless are very high.⁵

For a system of screening to be viable it must fulfil certain criteria:

• The condition must be sufficiently common to merit screening. This does not necessarily mean common in the whole population unless there is universal screening. It means common in the target group for screening.
• There must be an effective intervention for the condition that is being sought.
• Screening must result in the condition being recognised at an earlier stage when intervention is more effective.
• There must be high specificity (low rate of false positives) and a very high sensitivity (very low rate of false negatives), although this is difficult to assess when evaluating a screening tool for depression.
• The screening test must be relatively cheap or else the cost per case detected is prohibitively expensive.
• It must be safe, easy to use and acceptable to the patient.

In one sense the General Medical Services' (GMS) contract has simplified the situation in identifying patients with coronary heart disease and diabetes as being prioritised for screening. However, practices still undertaking the National Enhanced Service are obliged to recognise depression at an early stage in any patient. This represents a considerable workload and it may be best to focus one's attentions on patients deemed to be 'at risk'.

NICE guidelines suggest screening in those with a past history of depression, significant physical illness - especially if it causes disability - and other mental health problems like dementia. Other situations where the chance of depression is very high include:

• Parkinson's disease where the disease is common but often missed
• Dementia where the two diseases can easily resemble each other
• The puerperium - screening may show positive results in as many as 11%⁷
• Alcoholism and drug abuse - it may be difficult to decide if depression is the cause or effect of substance abuse but it may be desirable to treat both
• Victims of abuse
• Physical disease like cancer, cardiovascular disease or diabetes
• Chronic pain⁸
• Stressful home environments
• The elderly
• Social isolation
• Unexplained symptoms

A number of screening and assessment tools have been validated and are generally available.

Initial screening in patients with coronary heart disease or diabetes

NICE recommend that for patients with these conditions, the following two questions should be used to screen for depression:

• During the last month have you been feeling down, depressed or hopeless?
• During the last month have you often been bothered by having little interest or pleasure in doing things?⁵

Assessing newly diagnosed patients

Three tools are recommended in the Quality and Outcomes Framework guidance.⁹ These are:

• Patient Health Questionnaire (PHQ-9) This is a nine-item questionnaire which helps both to diagnose depression and to assess severity. It is based directly on the diagnostic criteria for major depressive disorder in the Diagnostic and Statistical Manual Fourth Edition (DSM-IV). It takes about three minutes to complete. Scores are categorised as minimal (1-4), mild (5-9) , moderate (10-14), moderately severe (15-19) and severe depression (20-27). It can be downloaded free from the internet.¹⁰
• Hospital Anxiety and Depression Scale (HADS) Despite its name, this has been validated for use in primary care. It is designed to assess both anxiety and depression. It takes about 5 minutes to complete. The anxiety and depression scales each have seven questions and scores are categorised as normal (0-7), mild (8-10), moderate (11-14) and severe (15-21).¹¹
• Beck Depression Inventory® Second Edition (BDI-II) This also uses DSM-IV criteria. it takes about five minutes to complete. It is an assessment of the severity of depression and is graded as minimal (0-13), mild (14-19), moderate (20-28) and severe (29-36). It consists of 21 items to assess the intensity of depression in clinical and normal patients. Each item is a list of four statements arranged in increasing severity about a particular symptom of depression. It is also not free but can be purchased from the supplier's website.¹²

Other screening tests may be useful in particular situations. They include:

• Children's Depression Inventory (CDI) and Reynolds' Child Depression Scale (RCDS). Both of these can be used on children aged over 7.¹³
• The Center for Epidemiologic Studies Depression Scale (CES-D) and Reynolds' Adolescent Depression Scale (RADS) are more suitable for adolescents.¹⁴
• The Edinburgh Postnatal Depression Scale (EDPS) - a self-rating scale - is for puerperal depression.¹⁵
• The Geriatric Depression Scale (GDS) is suitable for older patients. Center for Epidemiologic Studies (CES), Beck and Zung depression assessment tools can also be used in the elderly.¹⁴
• Cornell Scale for Depression in Dementia (CSDD) is suitable for patients with dementia.¹⁴

Although screening tools are useful, they should not be a substitute for clinical judgement. The patient's history, family history and the existence of co-morbidities should be taken into account when diagnosing or assessing depression.