This guideline makes recommendations on the identification, treatment and management of depression in adults aged 18 years and older, in primary and secondary care. This guideline covers people whose depression occurs as the primary diagnosis; the relevant NICE guidelines should be consulted for depression occurring in the context of other disorders (see our topic page on depression).
Depression is a broad and heterogeneous diagnosis. Central to it is depressed mood and/or loss of pleasure in most activities. Severity of the disorder is determined by both the number and severity of symptoms, as well as the degree of functional impairment. A formal diagnosis using the ICD-10 classification system requires at least four out of ten depressive symptoms, whereas the DSM-IV system requires at least five out of nine for a diagnosis of major depression (referred to in this guideline as 'depression'). Symptoms should be present for at least 2 weeks and each symptom should be present at sufficient severity for most of every day. Both diagnostic systems require at least one (DSM-IV) or two (ICD‑10) key symptoms (low mood [in both ICD-10 and DSM-IV], loss of interest and pleasure [in both ICD-10 and DSM-IV] or loss of energy [in ICD-10 only]) to be present.
Increasingly, it is recognised that depressive symptoms below the DSM‑IV and ICD‑10 threshold criteria can be distressing and disabling if persistent. Therefore this updated guideline covers 'subthreshold depressive symptoms', which fall below the criteria for major depression, and are defined as at least one key symptom of depression but with insufficient other symptoms and/or functional impairment to meet the criteria for full diagnosis. Symptoms are considered persistent if they continue despite active monitoring and/or low-intensity intervention, or have been present for a considerable time, typically several months. For a diagnosis of dysthymia, symptoms should be present for at least 2 years. Both DSM-IV and ICD-10 have the category of dysthymia, which consists of depressive symptoms that are subthreshold for major depression but that persist (by definition for more than 2 years). There appears to be no empirical evidence that dysthymia is distinct from subthreshold depressive symptoms apart from duration of symptoms, and the term 'persistent subthreshold depressive symptoms' is preferred in this guideline.
It should be noted that classificatory systems are agreed conventions that seek to define different severities of depression in order to guide diagnosis and treatment, and their value is determined by how useful they are in practice. After careful review of the diagnostic criteria and the evidence, the Guideline Development Group decided to adopt DSM-IV criteria for this update rather than ICD-10, which was used in the previous guideline (NICE clinical guideline 23). This is because DSM-IV is used in nearly all the evidence reviewed and it provides definitions for atypical symptoms and seasonal depression. Its definition of severity also makes it less likely that a diagnosis of depression will be based solely on symptom counting. In practical terms, clinicians are not expected to switch to DSM-IV but should be aware that the threshold for mild depression is higher than ICD-10 (five symptoms instead of four) and that degree of functional impairment should be routinely assessed before making a diagnosis. Using DSM-IV enables the guideline to target better the use of specific interventions, such as antidepressants, for more severe degrees of depression.
A wide range of biological, psychological and social factors, which are not captured well by current diagnostic systems, have a significant impact on the course of depression and the response to treatment. Therefore it is also important to consider both personal past history and family history of depression when undertaking a diagnostic assessment (see appendix for further details).
Depression often has a remitting and relapsing course, and symptoms may persist between episodes. Where possible, the key goal of an intervention should be complete relief of symptoms (remission), which is associated with better functioning and a lower likelihood of relapse.
The guideline assumes that prescribers will use a drug's summary of product characteristics (SPC) and the 'British national formulary' (BNF) to inform their decisions made with individual patients.
This guideline recommends some drugs for indications for which they do not have a UK marketing authorisation at the date of publication, if they are already in use in the NHS for that indication, and there is good evidence to support that use. Off-label use is indicated in the recommendations.
Section 1.10.4 of this guideline updates recommendations made in NICE technology appraisal guidance on the use of electroconvulsive therapy for the treatment of depression only. The guidance in the NICE technology appraisal remains unchanged for the use of ECT in the treatment of catatonia, prolonged or severe manic episodes and schizophrenia.
Recommendation 184.108.40.206 of this guideline updates recommendations in NICE technology appraisal guidance on computerised cognitive behaviour therapy for depression and anxiety for the treatment of depression only.