Last edited 08/2018 and last reviewed 06/2022

Depression is a mood disorder in which the predominant feelings are of sadness.

Depression describes an individual episode of mood disorder.

A depressive episode may be part of a lifetime pattern of mood disorder. The common lifetime diagnoses which include depressive episodes are:

  • recurrent depressive disorder
  • bipolar affective disorder
  • persistent affective disorders

NICE note that 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
      • 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, loss of interest and pleasure or loss of energy ) 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
    • the most recent NICE 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 .)
  • case identification and recognition
    • NICE advice that clinicians should be alert to possible depression (particularly in people with a past history of depression or a chronic physical health problem with associated functional impairment) and consider asking people who may have depression two questions, specifically:
      • during the last month, have you often been bothered by feeling down, depressed or hopeless?
      • during the last month, have you often been bothered by having little interest or pleasure in doing things?
    • if the person answers 'yes' to either question
      • a practitioner who is competent in mental health assessment should:
        • review the person's mental state and associated functional, interpersonal and social difficulties
        • consider using a validated measure for symptoms, functions and/or disability
      • a practitioner who is not competent in mental health assessment should:
        • refer the person to an appropriate professional - if this is not the person's GP, inform the GP

    • when assessing a person with suspected depression, consider using a validated measure (for example, for symptoms, functions and/or disability) to inform and evaluate treatment

    • for people with significant language or communication difficulties, for example people with sensory impairments or a learning disability, consider using the Distress Thermometer and/or asking a family member or carer about the person's symptoms to identify possible depression. If a significant level of distress is identified, investigate further