If you'd like to support us and get something great in return, check out our awesome products:

To be the first to know about our latest videos, subscribe to our YouTube channel 🙌


Depression is a mood (affective) disorder characterised by persistent low mood and loss of interest and enjoyment in everyday activities.

It can be unipolar (first occurrence or recurrent) or bipolar (with reoccurrences of mania and depression).

The onset of individual episodes is often related to stressful events or situations and it usually runs a relapsing and remitting course.

Depression is common, with the prevalence in the United Kingdom estimated to be approximately 4.5%. 

You might also be interested in our medical flashcard collection which contains over 1000 flashcards that cover key medical topics.
 The categorisation of depression
Figure 1. The categorisation of depression


In depression, aetiology is typically multifactorial with a combination of biological, psychological and social factors. These factors can be predisposing, precipitating or perpetuating (Figure 2).

Depression aetiology table
Figure 2. An overview of the aetiology of depression

Protective factors must also be considered including:

  • No family history of depression
  • Current employment
  • Good social support

Biological factors

Biological factors which increase the risk of depression include:

  • Genetics: family history of depression in the nuclear family increases the risk to almost 30-40% and up to 50% in monozygotic twins
  • Personality: dependent, anxious and avoidant traits
  • Physical illness: hypothyroidism or chronic illnesses
  • Biochemical theories/monoamine deficiency: serotonin imbalance causes depressive symptoms
  • Neuroendocrine: hypothalamic-pituitary-adrenal axis
  • Co-morbid substance misuse
  • Medication use: beta-blockers, steroids
  • History of other mental illnesses: anxiety

Psychological factors

Psychological factors which increase the risk of depression include:

  • Negative automated thoughts (e.g. helplessness, hopelessness, worthlessness)
  • Traumatic life events
  • Environmental factors (e.g. support)
  • Lack of education

Social factors

Social factors which increase the risk of depression include:

  • Poor social support
  • Poor economic status or support

Clinical features

 A diagnosis of a depressive episode requires the following:

  • The presence of symptoms for at least 2 weeks (this may be less if depression is severe)
  • The symptoms are not attributable to other organic or substance causes (e.g. normal bereavement)
  • The symptoms impair daily function and cause significant distress

For more information, see the Geeky Medics guide to depression history taking. 

Core symptoms of depression include:

  • Low mood
  • Anhedonia
  • Lack of energy (anergia)

Cognitive symptoms of depression include:

  • Decreased concentration
  • Impaired memory
  • Pessimistic and self-blaming
  • Nihilistic

Risk assessment

It is important to conduct a risk assessment, including: 

  • Risk to self: self-harm, suicide or neglect (commonest in depression)
  • Risk to others: technically low-risk, unless psychotic features such as command hallucinations are present

For more information, see the Geeky Medics guide to suicide risk assessment. 


Depression is graded as mild, moderate or severe.

  • Mild depression requires two core or main plus at least two cognitive symptoms.
  • Moderate depression requires two core or main plus at least three or four cognitive symptoms.
  • Severe depression requires all three core of main plus at least five cognitive symptoms.

The ICD-10 criteria (1994) for unipolar depression are as follows:

  1. Mild depressive episode, with or without somatic symptoms
  2. Moderate depressive episode, with or without somatic symptoms
  3. Severe depressive episode, with or without psychotic symptoms: these may be mood-congruent or incongruent psychotic symptoms

Somatic symptoms

Somatic symptoms of depression may include:

  • Marked loss of appetite or weight loss (some people experience the opposite)
  • Marked loss of libido
  • Sleep disturbances with early morning awakening (usually 2 hours or more before the usual time)
  • Diurnal variation of mood (worse in the mornings)
  • Psychomotor retardation or agitation: objective evidence, remarked on or reported by other people

The table below provides a clearer description of when with or without somatic symptoms is used, as per the ICD-10 classification.

ICD-10 classification of depression severity
Figure 3. ICD-10 classification of depression severity

Symptoms of psychosis

The two main symptoms of psychosis to consider are hallucinations (commonly auditory, less commonly olfactory; visual; tactile) and delusions (e.g. nihilistic or persecutory).

These symptoms of psychosis can be:

  • Mood-congruent (delusions/hallucinations that are consistent with typical depressive themes of, for example guilt)
  • Mood-incongruent (delusions/hallucinations that are not consistent with typical depressive themes; including more first rank symptoms, for example thought insertion).


Management is based on the bio-psycho-social model and is divided into short-term and long-term strategies. 

Management is dependent on symptoms the individual has (e.g. difficulty sleeping).

It is important to educate patients about the disease and provide both written and verbal information to patients. The Royal College of Psychiatrists published a patient information leaflet for depression. 

Depression management
Figure 4. An overview of depression management

Mild depression

Short-term management

First-line management should involve low-intensity psychosocial interventions:

  • Computerised cognitive-behavioural therapy (CCBT)
  • Individualised CBT or individual guided self-help based on CBT principles
  • Structured group physical activity programme

Exceptional cases to consider starting on biological therapy (i.e. antidepressants):

  • Past history of moderate or severe depression
  • Presence of mild depression that has been present for at least 2 years
  • Presence of mild depressive symptoms after other interventions

Long-term management

Long term management of mild depression includes:

  • Risk assessment
  • Ongoing review: response to low-intensity psychosocial intervention, compliance and symptoms
  • Measurement scales to assess response to treatment and quality of life
  • Relapse prevention plan
  • Assess for social support and previous issues flagged up during consultations
  • If they are on antidepressant therapy review compliance, use, side effects and adjust doses if appropriate

Moderate or severe depression

Short-term management

First-line management involves a combination of antidepressant therapy (biological treatment) and high-intensity psychosocial interventions which will depend on if they have/do not have a chronic physical health problem (see below).

If they are presenting with a severe depressive episode with psychotic symptoms, then augmenting treatment with an antipsychotic (aripiprazole, risperidone, quetiapine or olanzapine)

For people without a chronic physical health problem:

  • Individual CBT
  • Interpersonal therapy
  • Behavioural activation
  • Behavioural couples therapy

For people with a chronic physical health problem:

  • Group-based CBT
  • Individual CBT
  • Behavioural couples therapy

Long-term management

Long-term management of moderate or severe depression includes:

  • Risk assessment
  • Review their response to high-intensity psychosocial intervention compliance and symptoms
  • Review their response to antidepressant therapy, compliance, side effects and adjust doses if appropriate.
  • Measurement scales to assess response to treatment and quality of life
  • Relapse prevention plan
  • Assess social support and previous issues flagged up during the consultation


Complications of depression include:4

  • Suicide: the risk of suicide in patients with depression is four times higher than in patients without depression
  • Reduced quality of life: patients may struggle with employment and relationships
  • Antidepressant side effects: may include sexual dysfunction, risk of self-harm, weight gain, hyponatraemia and agitation

Persistent depression develops in approximately one in ten patients with depression. 


Dr Nusrat Khan

Clinical Associate Professor and Consultant Psychiatrist

Newcastle University


Dr Chris Jefferies


  1. Greg Lydall, M.D., Noreen Jakeman, Sheena Webb (2009) ‘Affective Disorders’, in Sarah Stringer, L.C., Susan Davison, Maurice Lipsedge (ed.) Psychiatry P.R.N. Oxford University Press
  2. ICD-10 (1994) ICD-10 Churchill Livingstone
  3. M Justin Coffey, M. (2017) Catatonia: Treatment and prognosis. Available from: [LINK]
  4. National Institute for Health and Care Excellence. Depression in adults: recognition and management. Published in 2009. Available from: [LINK]

Print Friendly, PDF & Email