Medically Fit For Exams
Medically Fit For Exams



A very common mental health illness, characterised by low mood and loss of pleasure


Risk factors

  • Female
  • Family history
  • Previous depressive episodes
  • Other mental health illness
  • Chronic illness
  • Stressful life events
  • Lack of social support
  • Low SES
  • Substance abuse


Differential diagnoses

  • Bipolar disorder/cyclothymia
  • Dysthymia
  • SAD
  • Postnatal depression
  • Dementia (AD/Parkinson’s)
  • Anxiety disorder
  • Medication side effect
  • Hypothyroidism
  • Anorexia nervosa



  • More common in females
  • Affects up to 1/3 at some point in their life
  • Prevalence of 5-10% in primary care settings
  • Worldwide, more common in Western countries
  • Leading cause of disability and death in 18-44 age category



  • Unknown, several genes implicated, eg 5HTLLR
  • May be a result of abnormal serotonin function/levels
  • May be a direct response to life events


Clinical features

  • Persistent low mood/sadness (>2 weeks)
  • Anhedonia (loss of pleasure)
  • Fatigue/lethargy
  • Low self-confidence
  • Guilt/self-blame
  • Suicidality/suicidal thoughts
  • Reduced libido
  • Change in appetite
  • Change in sleep habits, especially early morning waking
  • Change in weight (in line with appetite changes normally)
  • Cognitive impairment (memory, concentration, decision making)
  • Delusions/hallucination (psychotic depression)
  • Physical symptoms (more common in elderly)
    • Pain
    • Constipation



  • Abnormal serotonergic function
    • Is not the simple low serotonin à depression model that was originally postulated (monoamine hypothesis)
    • Serotonin is likely to have a neuromodulatory effect that is much more complex than this
      • Supported by effects of 5HTLLR polymorphism paradoxical effects: having at least one S-allele increases risk of depression, although this acts to increase serotonin availability. Also, S-allele only conveys increased risk if also have stressful (early) life events – if supportive early environment, S-allele PROTECTS against depression)
      • Paradoxical effects of tetracyclic drugs – agonists of reuptake molecules
  • Abnormal HPA activity (increased cortisol levels)



  • Clinical diagnosis
  • Rule out other causes



  • Antidepression medication
    • Monoamine oxidase inhibitors (MOAIs) – inhibit MOA, which breaks down serotonin and NE in the synapses. MOA-A and MOA-B. Inhibiting MOA-B can lead to hypertensive crisis if tyramine rich foods (cheese, caviar) are eaten. Are many side effects, as is not specific. Very rarely used
    • Tricyclic anti-depressants (TCAs) – inhibit serotonin and NE reuptake in synapses. Are not specific, and lead to many side effects, eg dry mouth, blurred vision, urinary retention, constipation, drowsiness, sedation, postural hypotension. Are dangerous in overdose, so not given to suicidal
      • Eg amitriptyline
    • Selective serotonin reuptake inhibitors (SSRIs) – Selectively inhibit serotonin reuptake, so fewer side effects that TCAs. Side effects still include sexual dysfunction, diarrhoea, insomnia, nausea, drug interactions (inhibition of CYP450). For use in moderate depression, not in bipolar
      • Eg fluoxetine, sertraline, citalopram
    • Serotonin + noradrenaline reuptake inhibitors (SNRIs) – Inhibit NE and 5-HT reuptake, so increase concentration in synapse. Side effects = dizziness, sedation, sexual dysfunction. Used in moderate to severe depression
      • Eg venlafaxine, duloxetine
    • Tetracyclic anti-depressants – reuptake AGONISTS, mechanism of action seems paradoxical, effects on downstream emotion processing and serotonin regulation
  • Cognitive/behavioural therapy
    • Is similarly effective to medical treatment
    • Involves goal setting, reward systems, cognitive-reattribution, attention and cognition training
    • Is most effective when paired with medical treatment
  • Electro-convulsive therapy – electric current passed through brain. Is the most effective form of treatment, but only used in severe and/or treatment resistant depression



  • Treatment not always effective
  • Recurrence is very common
  • Increased suicide risk
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