Depression
A persistent disorder of mood, motivation and cognition that is diagnosed clinically and, at moderate-to-severe intensity, responds to antidepressants and structured psychological therapy.
In a nutshell
A sustained failure of the reward-and-arousal circuits, so it is never just sadness: sleep, appetite, psychomotor speed and cognition go with it. Diagnosis is clinical, and the intensity of treatment is set by severity and risk rather than by the label.
Classic presentation
Two or more weeks of persistent low mood and anhedonia with early-morning waking, appetite change, poor concentration and guilt, impairing function, and no history of mania.
Key points
- Low mood and anhedonia are the two core symptoms. The biological symptoms (sleep, appetite, energy, psychomotor change) arise from the same monoamine circuits, which is why they travel together.
- Screen for past mania or hypomania. If present, the diagnosis is bipolar disorder and an antidepressant alone may do harm.
- Exclude organic mimics: hypothyroidism, anaemia, hypercalcaemia and B12 deficiency all reproduce fatigue and low mood.
- Severity and risk drive treatment: a lower-intensity psychological intervention for less severe depression, an antidepressant and/or high-intensity therapy for more severe.
- SSRIs are the usual first-line class. Benefit takes two to four weeks because the therapeutic event is downstream adaptation, not the immediate rise in synaptic monoamine.
- Review early, especially in younger adults: energy and drive can return before mood lifts, transiently raising suicide risk.
First-line investigation
A structured severity questionnaire such as PHQ-9 alongside a risk assessment, with bloods (FBC, TFTs, calcium, glucose, B12 and folate) to exclude organic mimics.
First-line management
Grade severity and assess suicide risk first, then match the intervention: psychological therapy for less severe depression, an antidepressant and/or high-intensity therapy for more severe.
Exam traps
- A patient with past hypomania has bipolar disorder, not unipolar depression, however depressed they are today.
- The delay to benefit is the reason for the early review: activation can precede mood improvement and raise short-term risk.
- Antidepressants are continued beyond remission and withdrawn slowly. Stopping at recovery invites relapse and discontinuation symptoms.
- New severe depression in an older adult should prompt a search for an organic cause.
Educational content pending clinical review. Not medical advice.