- 14-18% lifetime prevalence
- 20% of cases are chronic
- Genetic risk
- Increased risk if first degree relative affected (3x)
- Twin studies- MZ (27%) vs DZ (12%)
- Hereditability of major depression is around 70%
- More common in females than males (2:1) and mean age of onset is 27 years old.
- Onset can be associated with excess adverse life events- mainly exit events (e.g. death/bereavement, separation etc) or negative early experiences e.g. abuse or neglect.
- ICD-10 splits depressive episodes into mild, moderate and severe depression +/- the presence of somatic or psychotic symptoms.
- DSM IV splits depression into just minor and major; ICD-10 splits into mild, moderate and severe.
Symptoms must be clearly abnormal for the individual concerned, it must persist for more than 2 weeks (without previous history of mood disorder), and it should interfere with normal function to a significant degree.
In moderate depression, there should be 2; and in severe depression, all of the following typical symptoms:
- Low mood to a degree that is definitely abnormal for the patient; present for most of the day; largely uninfluenced by circumstance; and present for at least 2 weeks
- Loss of interest or pleasure in activities that are usually enjoyable (anhydonia)
- Decreased energy or increased fatigue
PLUS >=4 (moderate) or >4 (severe) of:
- Loss of confidence/self esteem
- Unreasonable feelings of self-reproach or excessive and unreasonable guilt
- Recurrent thoughts of death/suicide, or any suicidal behaviour
- Complaints or evidence of diminished ability to think or concentrate e.g. indecisiveness
- Changes in psychomotor activity, with agitation or retardation (either objective or subjective)
- Sleep disturbance
- Change in appetite with corresponding change in weight
Although the diagnosis of severe/moderate/mild depression are made on the number of symptoms, there are various other ways of assessing the severity of depression.
- Rating scales e.g. Hamilton rating scale for depression; Montomery-Asberg depression scale; Beck depressive inventory (NB Beck’s cognitive triad- negative view of self, others and the future)
Subtypes of depression
- Somatic syndrome
- Psychotic depression
- Postnatal depression
- Chronic (treatment-refractory) depression
Progression / Timeline
The 5 ‘R’s’ are a good way of thinking about it: