Mood Disorders
This domain tests the diagnosis, classification and staged treatment of unipolar and bipolar mood disorder, including the recognition of bipolarity hidden inside a depressive presentation.
Diagnostic rules
Major depressive disorder requires five of nine symptoms for at least two weeks, with at least one being depressed mood or anhedonia, plus impairment. Always exclude bipolar disorder, substance causes and medical causes (hypothyroidism, anaemia, B12 deficiency, sleep apnoea, steroid use, post-stroke depression).
Specifiers change treatment: melancholic features, psychotic features, atypical features, peripartum onset, seasonal pattern, catatonia, and mixed features.
Bipolar I requires a manic episode of at least one week, or any duration if hospitalisation is needed, with three or four of the classic symptoms (elevated mood, increased activity, pressured speech, flight of ideas, reduced sleep, grandiosity, distractibility, reckless behaviour). Bipolar II requires hypomania of at least four days without marked impairment, plus major depression. Rapid cycling means four or more episodes in a year.
Treatment logic
In bipolar mania, first-line agents are antipsychotics (haloperidol, olanzapine, risperidone, quetiapine) with or without lithium or valproate. In bipolar depression, quetiapine, lamotrigine or lithium are preferred; antidepressant monotherapy risks switch and cycling and is avoided. Maintenance treatment with lithium has the additional advantage of reducing suicide. In unipolar depression, mild illness responds to psychological therapy, moderate to severe illness to an SSRI plus therapy, and psychotic depression needs an antipsychotic, ECT, or both.
Worked example
A 23-year-old presents with a third depressive episode. She has a family history of bipolar disorder, atypical features with hypersomnia and leaden paralysis, and once became elated and sleepless for five days on an SSRI. Reasoning: the prior activation and family history point to bipolar spectrum illness. The safest plan is a mood stabiliser with careful monitoring rather than another antidepressant alone.
Traps that cost marks
Missing bipolarity in early-onset recurrent depression. Labelling normal bereavement as major depression. Forgetting that suicide risk rises early in recovery and in mixed states. Under-dosing or stopping antidepressants before six to twelve months of continuation. Ignoring lithium's anti-suicide effect in maintenance planning.