Both ICD10 and DSM5 distinguish between single and recurrent depressive episodes and between mild, moderate and severe depression.

DSM 5 says the person must have experienced at least five symptoms, one of which must be depressed mood and loss of interest interests or pleasure while ICD10 says the person may have four symptoms, so long as they have experienced at least two of the following: depressed mood, loss of interest/enjoyment and/or increased fatigability.

Both systems require symptoms to be present for at least two weeks and the DSM suggests that a person’s subjective distress and social/occupational functioning must also be considered.