Major depressive disorder (MDD) is one of the most common and disabling mental health conditions worldwide, affecting approximately 280 million people. It is characterized by persistent low mood, loss of interest or pleasure in activities (anhedonia), changes in sleep and appetite, fatigue, difficulty concentrating, feelings of worthlessness or guilt, and in severe cases, thoughts of death or suicide. Depression is not a character flaw or a sign of weakness — it is a medical condition involving complex alterations in brain chemistry, neural circuitry, and neuroendocrine function that responds to evidence-based treatment. This guide provides a comprehensive overview of the pharmacological options available for treating depression.

Not all depression requires medication. For mild depression, structured psychological therapies such as cognitive behavioral therapy (CBT) or behavioral activation are often sufficient as initial treatment. However, antidepressant medication is recommended as first-line treatment for moderate-to-severe depression, or for mild depression that has not responded to psychological interventions alone. Medication is also strongly indicated when there is significant functional impairment (inability to work, care for oneself, or maintain relationships), presence of psychotic features, high suicide risk, history of recurrent episodes, or patient preference after informed discussion. The most effective approach for moderate-to-severe depression is typically combination therapy — medication plus structured psychotherapy — which produces better outcomes than either treatment alone.

Selective serotonin reuptake inhibitors (SSRIs) are the most widely prescribed antidepressants and the recommended first-line pharmacological treatment in virtually all current guidelines. They work by selectively blocking the reuptake of serotonin (5-HT) at the presynaptic terminal, increasing serotonin availability in the synaptic cleft. Common SSRIs include: Sertraline (50–200 mg/day) — often considered the overall first choice due to its favorable balance of efficacy, tolerability, and drug interaction profile; particularly suitable for patients with comorbid anxiety. Escitalopram (10–20 mg/day) — the most selective SSRI with excellent tolerability; strong evidence base. Fluoxetine (20–60 mg/day) — long half-life (advantageous for adherence but takes longer to wash out); preferred in adolescents. Citalopram (20–40 mg/day) — dose ceiling of 40 mg due to QTc prolongation risk at higher doses. Paroxetine (20–50 mg/day) — effective but has the highest risk of discontinuation syndrome among SSRIs and notable anticholinergic effects. Fluvoxamine (100–300 mg/day) — often used preferentially for OCD. Common SSRI side effects include nausea, headache, insomnia or drowsiness, sexual dysfunction (decreased libido, anorgasmia, delayed ejaculation — affects 30–70% of patients), weight changes, and increased anxiety in the first 1–2 weeks. Most side effects diminish over 2–4 weeks of treatment.

Serotonin-norepinephrine reuptake inhibitors (SNRIs) block the reuptake of both serotonin and norepinephrine, providing dual monoamine modulation. They may be preferred when SSRIs are insufficient or when depression is accompanied by significant pain symptoms or fatigue. Key SNRIs include: Venlafaxine (75–375 mg/day) — widely used, effective for both depression and generalized anxiety disorder; dose-dependent norepinephrine reuptake inhibition (acts primarily as an SSRI at lower doses, adding norepinephrine effect at ≥150 mg/day); monitor blood pressure as it can cause dose-dependent hypertension. Duloxetine (60–120 mg/day) — approved for depression, generalized anxiety, diabetic neuropathic pain, fibromyalgia, and chronic musculoskeletal pain; a versatile choice for patients with comorbid pain conditions. Desvenlafaxine (50 mg/day) — the active metabolite of venlafaxine with a simpler dosing regimen and fewer drug interactions. SNRI side effects are similar to SSRIs but additionally include elevated blood pressure, increased sweating, and potentially more pronounced discontinuation symptoms.

Tricyclic antidepressants (TCAs) were among the first antidepressants developed and remain effective options, particularly for treatment-resistant depression. They block reuptake of serotonin and norepinephrine (like SNRIs) but also have significant activity at histamine H1, muscarinic, and alpha-1 adrenergic receptors, which accounts for their broader side effect profile. Key TCAs include amitriptyline (75–150 mg/day — also used for neuropathic pain, migraine prevention, and insomnia), nortriptyline (50–150 mg/day — better tolerated, used with therapeutic drug monitoring), clomipramine (75–250 mg/day — most serotonergic TCA, particularly effective for OCD), and imipramine (75–200 mg/day). Side effects include dry mouth, constipation, urinary retention, blurred vision (anticholinergic), sedation, orthostatic hypotension, weight gain, and cardiac conduction abnormalities. TCAs have a narrow therapeutic index — overdose can be fatal, making them less suitable for patients with suicide risk. Monoamine oxidase inhibitors (MAOIs) such as phenelzine and tranylcypromine are highly effective but rarely used due to dietary restrictions (tyramine-containing foods can trigger hypertensive crisis) and extensive drug interactions. They are reserved for treatment-resistant depression.

Several antidepressants do not fit neatly into the above categories. Bupropion (150–450 mg/day) — a norepinephrine-dopamine reuptake inhibitor (NDRI) that is unique among antidepressants in having no sexual side effects and often promoting weight loss rather than gain. It is particularly useful for patients with prominent fatigue, poor concentration, or those who have experienced sexual dysfunction with other antidepressants. Contraindicated in patients with seizure disorders or eating disorders. Also approved for smoking cessation. Mirtazapine (15–45 mg/day) — a noradrenergic and specific serotonergic antidepressant (NaSSA) that blocks alpha-2 adrenergic autoreceptors and specific serotonin receptors (5-HT2 and 5-HT3). Its potent antihistamine effect causes sedation and appetite stimulation, making it particularly useful for patients with insomnia and poor appetite/weight loss. Paradoxically, sedation may be greater at lower doses (15 mg) than higher doses. Trazodone (150–300 mg for depression, 25–100 mg for insomnia) — a serotonin antagonist and reuptake inhibitor (SARI) more commonly used at low doses as a sleep aid than at antidepressant doses. Vortioxetine (10–20 mg/day) — a multimodal serotonergic antidepressant with evidence for cognitive benefits in depression. Agomelatine (25–50 mg/day) — a melatonin MT1/MT2 receptor agonist and 5-HT2C antagonist that improves sleep architecture without causing daytime sedation; requires liver function monitoring.

Selecting an antidepressant involves matching the drug's profile to the patient's specific symptoms, comorbidities, and priorities. For depression with prominent insomnia — mirtazapine, trazodone, or amitriptyline. For depression with fatigue and low motivation — bupropion, venlafaxine, or duloxetine. For depression with comorbid anxiety — sertraline, escitalopram, or venlafaxine. For depression with chronic pain — duloxetine, venlafaxine, or amitriptyline. For depression with concern about sexual dysfunction — bupropion, mirtazapine, or vortioxetine. For depression with concern about weight gain — bupropion or fluoxetine. Previous personal or family response to a specific antidepressant is one of the strongest predictors of efficacy. All antidepressants take 2–4 weeks to begin showing therapeutic effects and 6–8 weeks for full response. It is critical not to discontinue prematurely. If no response after 4–6 weeks at adequate dose, options include dose optimization, augmentation, or switching to a different agent.

Proactive side effect management improves adherence and outcomes. Sexual dysfunction — the most common reason for non-adherence; options include switching to bupropion or mirtazapine, adding bupropion as augmentation, dose reduction, or scheduled drug holidays (for short half-life agents only, under medical supervision). GI effects (nausea) — take with food, start at low dose, usually resolves within 1–2 weeks. Weight gain — most common with mirtazapine, paroxetine, and TCAs; lifestyle measures, or consider switching to a weight-neutral agent. Insomnia/activation — take medication in the morning, ensure sleep hygiene; short-term use of low-dose trazodone may help. Serotonin syndrome — a rare but potentially life-threatening condition caused by excessive serotonergic activity, typically from combining multiple serotonergic agents. Symptoms include agitation, hyperthermia, myoclonus, hyperreflexia, and autonomic instability. Requires immediate medical attention.

Abruptly stopping or rapidly tapering antidepressants — particularly paroxetine, venlafaxine, desvenlafaxine, and duloxetine — can cause discontinuation syndrome. Symptoms include dizziness, nausea, headache, irritability, insomnia, "brain zaps" (electric shock-like sensations), flu-like symptoms, and sensory disturbances. Symptoms typically begin within 1–3 days of stopping and can last 1–3 weeks (sometimes longer with venlafaxine and paroxetine). Prevention involves gradual tapering over at least 4 weeks, with slower tapers for longer treatment durations. For patients on paroxetine or venlafaxine who struggle with tapering, a strategy of switching to fluoxetine (which has a very long half-life and rarely causes discontinuation symptoms) before final discontinuation can be helpful. It is important to distinguish discontinuation syndrome from relapse — discontinuation symptoms typically appear rapidly and improve with reinstatement, while relapse develops gradually over weeks.

Approximately 30% of patients with MDD do not achieve adequate response after two or more adequate antidepressant trials, a condition termed treatment-resistant depression (TRD). Management strategies include: Augmentation — adding lithium (well-established augmentation agent), an atypical antipsychotic (aripiprazole, quetiapine, olanzapine), or triiodothyronine (T3, 25–50 mcg/day). Switching to a different class of antidepressant. Esketamine (intranasal, brand name Spravato) — approved for TRD in combination with an oral antidepressant; administered in a clinical setting under supervision due to dissociative effects and risk of sedation. Electroconvulsive therapy (ECT) — remains the most effective treatment for severe, treatment-resistant depression, with response rates of 50–70%; modern ECT under anesthesia is safe and well-tolerated. Transcranial magnetic stimulation (TMS) — a non-invasive neuromodulation technique approved for TRD. Psychedelic-assisted therapy with psilocybin is in advanced clinical trials and showing promising results.

Key medications discussed in this guide include sertraline, escitalopram, fluoxetine, citalopram, paroxetine, venlafaxine, duloxetine, bupropion, mirtazapine, amitriptyline, nortriptyline, trazodone, vortioxetine, and agomelatine. For more information, explore related conditions on PillsCard: anxiety disorders, insomnia, chronic pain, and migraine.