TL;DR
- •Mirtazapine (Remeron) and Trazodone are both antidepressants with strong sedating effects — frequently prescribed when depression coexists with insomnia.
- •Trazodone at low doses (25-100mg) is primarily used as a sleep aid; antidepressant doses are higher (150-400mg). Many patients take it for sleep without it acting as an antidepressant.
- •Mirtazapine is dosed as an antidepressant first (15-45mg); the sleep effect is a built-in side benefit. Lower doses are MORE sedating due to histamine receptor saturation.
- •Mirtazapine causes weight gain (often substantial — 5-15 lbs); Trazodone is generally weight-neutral.
- •Trazodone carries a rare but significant risk of priapism (painful prolonged erection) — males should be counseled.
- •For treatment-resistant depression with severe insomnia, ketamine's rapid mechanism can improve both mood and sleep alongside whichever of these is the maintenance medication.
Side by side
Mirtazapine
Mirtazapine (brand: Remeron)
Atypical antidepressant (NaSSA — noradrenergic and specific serotonergic)
What it treats
Major depression, Off-label: insomnia with depression, anxiety, anorexia, augmentation with SSRIs
Mechanism
Blocks alpha-2 adrenergic autoreceptors (increasing norepinephrine and serotonin release) plus blocks 5-HT2A, 5-HT2C, 5-HT3 and H1 histamine receptors. The H1 blockade drives the strong sedation, especially at low doses.
Strengths
- •No sexual dysfunction (does not block serotonin reuptake)
- •Anti-emetic effect helps depressed patients with nausea
- •Promotes appetite and weight gain (asset in underweight/anorexic patients)
- •Strong sleep improvement at antidepressant doses
Limitations
- •Weight gain — often 5-15 lbs (the most common reason for discontinuation)
- •Sedation can be excessive especially in early weeks
- •Rare neutropenia / agranulocytosis (very rare but real)
- •Vivid dreams or nightmares in some patients
Trazodone
Trazodone
Serotonin Antagonist and Reuptake Inhibitor (SARI)
What it treats
Major depression (at 150-400mg doses), Off-label: insomnia at 25-100mg doses
Mechanism
Blocks serotonin reuptake (modest) plus antagonizes 5-HT2A/2C receptors and H1 histamine receptors. Multi-receptor profile produces sedation prominently at lower doses.
Strengths
- •Cheap, widely available, generic for decades
- •Effective non-controlled-substance sleep aid alternative to benzos/Z-drugs
- •Weight-neutral
- •No sexual dysfunction at typical sleep doses
Limitations
- •Priapism risk (rare but medical emergency — males should know symptoms)
- •Orthostatic hypotension (dizziness on standing)
- •Antidepressant doses (300-400mg) are too sedating for most patients to tolerate during the day
- •Mild but real CYP3A4 interactions
Which one for your situation?
If:
Patient needs an antidepressant AND has severe insomnia
Verdict:
Mirtazapine — both effects come from one medication at one dose
If:
Patient just needs help sleeping, doesn't need an antidepressant
Verdict:
Trazodone — 25-100mg as sleep aid; not antidepressant range
If:
Patient is underweight or has poor appetite
Verdict:
Mirtazapine — its weight-gain side effect is a feature, not a bug
If:
Patient is concerned about weight gain
Verdict:
Trazodone — weight-neutral; consider also Wellbutrin or other non-sedating options
If:
Already on an SSRI with partial response and insomnia
Verdict:
Either as augmentation — mirtazapine is more common in clinical practice for this scenario
If:
Treatment-resistant depression after multiple antidepressant trials
Verdict:
Mechanism switch (ketamine) is higher-yield than another sedating antidepressant
Where ketamine fits
For patients with treatment-resistant depression whose insomnia is depression-driven, ketamine's rapid mood response often improves sleep as a secondary benefit. Many patients reduce or discontinue trazodone/mirtazapine after ketamine response without insomnia returning.
Mirtazapine improves sleep within nights but full antidepressant effect takes 4-6 weeks. Trazodone improves sleep within nights but isn't a primary antidepressant at sleep doses. Sublingual ketamine produces mood response within hours of the first session.
5-minute screening · Reviewed by a board-certified physician · FL & NJ
Frequently asked
Why is trazodone the most-prescribed sleep medication?
It's non-controlled (unlike Ambien, benzos), doesn't cause dependence, is generic and cheap, and works for most patients with chronic insomnia where standard sleep medications aren't a good long-term solution. The off-label use for sleep is much more common than its on-label use as an antidepressant.
Will mirtazapine make me gain a lot of weight?
On average yes — 5-15 lbs over 6-12 months is typical. Some patients gain more. This is the #1 reason for discontinuation. If weight gain matters, discuss alternatives upfront (Wellbutrin, SSRIs, or trazodone-for-sleep + non-sedating antidepressant).
Is trazodone safe to take every night?
Yes, it's commonly prescribed for chronic insomnia and considered safer than benzos or Z-drugs for long-term use. The main long-term concerns are mild ones — morning grogginess if dose is too high, occasional dry mouth, and the rare priapism risk in males. Annual review with your prescriber is standard.
Can I take mirtazapine with my SSRI?
Yes — combining a serotonergic antidepressant with mirtazapine is called "California Rocket Fuel" (typically Effexor + mirtazapine but works with SSRIs too). It's a well-recognized augmentation strategy for partial responders or for adding sleep benefit. Your prescriber should review for serotonin syndrome risk.
My SSRI works but I still can't sleep. What's the best add-on?
Common options: trazodone 25-100mg at bedtime (low-cost, weight-neutral), mirtazapine 15mg at bedtime (broader antidepressant effect plus sleep), or melatonin/sleep hygiene first before adding medication. For treatment-resistant depression with persistent insomnia, ketamine often improves both mood and sleep without needing chronic sleep medications.
References
- Cipriani A et al. 2018, Lancet. Network meta-analysis ranking 21 antidepressants — mirtazapine ranked in the top efficacy tier; trazodone less efficacious for primary depression but useful as adjunct. PMID 29477251
- Murrough JW et al. 2013, American Journal of Psychiatry. Ketamine RCT in treatment-resistant depression — sleep symptoms often improve alongside core depression response. PMID 23982301