diagnostic criteria

Last edited 08/2018

NICE have now adopted DSM-IV for the diagnosis of depression (1):

DSM-IV versus ICD-10 classification

• DSM-IV is used in nearly all clinical trials 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
  • NICE though favouring DSM-IV note that 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

Assessment of depression is based on the criteria in DSM-IV. Assessment should include the number and severity of symptoms, duration of the current episode, and course of illness. Key symptoms:

• persistent sadness or low mood; and/or
• marked loss of interests or pleasure
• at least one of these, most days, most of the time for at least 2 weeks
  
  
• if any of above present, ask about associated symptoms:
  • disturbed sleep (decreased or increased compared to usual)
  • decreased or increased appetite and/or weight
  • fatigue or loss of energy
  • agitation or slowing of movements
  • poor concentration or indecisiveness
  • feelings of worthlessness or excessive or inappropriate guilt
  • suicidal thoughts or acts
    
    
• the duration and associated disability, past and family history of mood disorders, and availability of social support should also be asked about:
  
  
  • 1. factors that favour general advice and active monitoring:
    • four or fewer of the above symptoms with little associated disability
    • symptoms intermittent, or less than 2 weeks' duration
    • recent onset with identified stressor
    • no past or family history of depression
    • social support available
    • lack of suicidal thoughts
  • 2. factors that favour more active treatment in primary care:
    • five or more symptoms with associated disability
    • persistent or long-standing symptoms
    • personal or family history of depression
    • low social support
    • occasional suicidal thoughts
  • 3. factors that favour referral to mental health professionals:
    • inadequate or incomplete response to two or more interventions
    • recurrent episode within 1 year of last one
    • history suggestive of bipolar disorder
    • the person with depression or relatives request referral
    • more persistent suicidal thoughts
    • self-neglect
  • 4. factors that favour urgent referral to specialist mental health services
    • actively suicidal ideas or plans
    • psychotic symptoms
    • severe agitation accompanying severe symptoms
    • severe self-neglect.

DSM-IV severities of depression

• subthreshold depressive symptoms: fewer than 5 symptoms
• Mild depression: few, if any, symptoms in excess of the 5 required to make the diagnosis, and symptoms result in only minor functional impairment
• Moderate depression: symptoms or functional impairment are between 'mild' and 'severe'
• Severe depression: most symptoms, and the symptoms markedly interfere with functioning. Can occur with or without psychotic symptoms.

A diagnosis of dysthymia - this is a chronic depressive state (two years or more duration) which is not the consequence of a partly resolved major depression and does not meet the diagnostic criteria for major depression (2).

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 the NICE guidance (1).

An alternative method of assessment of depression is via the Beck depression inventory.

Reference:

1. NICE (April 2018). Depression.
2. Anderson IM et al (2000). Evidence-based guidelines for treating depressive disorders with antidepressants: a revision of the 1993 British Association for Psychopharmacology guidelines. J Psychopharmacol, 14, 3-20.