ICD 10 allocates diagnostic symptoms to 2 clusters:
Cluster A ("core symptoms")
Low mood
Loss of enjoyment
Reduced energy
Cluster B (additional symptoms)
Reduced concentration
Reduced self-esteem
Ideas of guilt
Ideas of self harm
Pessimistic thoughts
Disturbed sleep
Disturbed appetite
Mild depression = at least 2 from A and 2 from B
Moderate depression = at least 2 from A and 3 from B
Severe depression = all 3 from A and at least 4 from B