Affective disorders include depression, bipolar disorder, dysthymia and cyclothymia.
Depression may be unipolar, bipolar, or secondary to physical illness, medication, alcohol/drugs, or psychosocial stress.
Often relapsing-remitting; previous depression increases future relapse and suicide risk.

🩺 Depression: Key Features

Core: low mood, anhedonia, low energy.
Associated: poor sleep, appetite/weight change, poor concentration, guilt/worthlessness, psychomotor change, reduced libido, suicidal thoughts.
DSM-5: ≥5 symptoms for ≥2 weeks, including low mood or anhedonia, with functional impairment.

🔍 Assessment

Assess mood, function, self-neglect, psychosis, substance use and physical illness.
Always ask about suicide/self-harm: thoughts, plans, intent, means, previous attempts and protective factors.
Screen for bipolarity: elevated mood, reduced sleep, increased energy, pressured speech, grandiosity, overspending or risk-taking.
Consider tests where relevant: FBC, U&E, LFT, TFT, B12/folate, glucose/HbA1c, medication review.

🌤️ Bipolar Clues

Past episodes of mania/hypomania suggest bipolar disorder.
Avoid antidepressant monotherapy if bipolar disorder is suspected.

🛠️ Management

Risk first: crisis team, urgent psychiatry or admission if high suicide risk, psychosis, severe self-neglect or risk to others.
Psychological: guided self-help, CBT, behavioural activation, interpersonal therapy.
Medication: SSRIs are common first-line antidepressants; review response and side effects.
ECT: consider for severe, psychotic, resistant or life-threatening depression.

Antidepressants can precipitate mania or hypomania, especially in undiagnosed bipolar disorder. Before starting an antidepressant, screen for previous mania/hypomania: reduced need for sleep, increased energy, grandiosity, pressured speech, overspending, disinhibition or risk-taking.

💊 Drug Notes

SSRIs: generally first line and safer in overdose.
SNRIs: option after SSRI failure; monitor side effects/BP.
TCAs: effective but anticholinergic and dangerous in overdose.
St John’s wort: avoid or use caution due to interactions.

💊 Common Medications: Doses & Prescribing Points

Drug / class	Typical adult dose	Key prescribing points
Sertraline SSRI	Start 50 mg OD. Usual range 50-200 mg OD.	Good first-line SSRI. Often preferred in cardiac disease. GI upset, sexual dysfunction, hyponatraemia, bleeding risk with NSAIDs/anticoagulants.
Citalopram SSRI	Start 20 mg OD. Max usually 40 mg OD. Max 20 mg OD in older adults or hepatic impairment.	QT prolongation risk. Avoid with other QT-prolonging drugs where possible. Consider ECG if cardiac risk.
Fluoxetine SSRI	Start 20 mg OD Usual range 20-60 mg OD.	Long half-life; useful if adherence variable, but interactions persist after stopping. Can be activating and worsen insomnia/anxiety early.
Mirtazapine NaSSA	Start 15 mg nocte. Usual range 15-45 mg nocte.	Useful if insomnia, poor appetite or weight loss. Can cause sedation, increased appetite and weight gain.
Venlafaxine MR SNRI	Start 75 mg OD Usual range 75-225 mg OD; higher doses usually specialist-led.	Monitor BP. More discontinuation symptoms if stopped abruptly. Avoid/caution in uncontrolled hypertension or significant arrhythmia risk.
Duloxetine SNRI	Usually 60 mg OD. Range 60-120 mg/day.	Useful if depression with neuropathic pain. Avoid in severe renal impairment or significant liver disease. Monitor BP and LFT risk factors.
Amitriptyline TCA	Depression doses are higher than pain doses; specialist/experienced prescribing often needed. Typical antidepressant range 75-150 mg/day.	Anticholinergic burden, sedation, postural hypotension, QT/QRS effects. Dangerous in overdose; avoid where suicide risk is significant.
Vortioxetine	Start 10 mg OD. Range 5-20 mg OD. Consider 5 mg OD in older adults.	Option after inadequate response/intolerance to other antidepressants. Nausea common. Fewer sexual side effects than some SSRIs in some patients.
Lithium Mood stabiliser	Dose is adjusted to plasma level, not fixed. Common start: 400 mg nocte, then titrate.	Specialist initiation. Check U&E/eGFR, TFT, calcium, weight/BMI ± ECG. Monitor lithium level 12 hours post-dose. Narrow therapeutic index; toxicity risk with dehydration, NSAIDs, ACE inhibitors, ARBs and diuretics.
Lamotrigine Mood stabiliser	Usually start 25 mg OD for 2 weeks, then slow titration.	Used particularly in bipolar depression/relapse prevention. Titrate slowly due to rash and rare Stevens-Johnson syndrome. Interacts with valproate and enzyme inducers.
Quetiapine Atypical antipsychotic	Bipolar depression: titrate to around 300 mg nocte depending on preparation and tolerance.	Useful in bipolar depression. Sedation, postural hypotension, weight gain, metabolic syndrome and QT risk. Monitor weight, BP, glucose/HbA1c and lipids.
Valproate Mood stabiliser	Dose varies; commonly specialist-led and titrated to response/levels.	Used in bipolar disorder but major teratogenic risk. Avoid in pregnancy and use only under strict pregnancy prevention rules where relevant. Monitor LFT, FBC, weight and metabolic effects.

⚠️ Prescribing safety: always check the current BNF, local formulary, renal/hepatic function, interactions, pregnancy status, overdose risk, and bipolar history before prescribing. Warn patients that antidepressants may take 2-4 weeks to start helping and should not be stopped abruptly.

🧠 Teaching Point

Depression is more than sadness: look for anhedonia, biological symptoms, impaired function and suicide risk. Always decide whether it is unipolar depression, bipolar disorder, or secondary to physical illness, medication or substances.

📚 References

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Low Mood and Affective Disorders - Depression

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