Comorbidity-based medication selection in psychiatry

Depression paired with something

Depression + insomnia

The mainstays: mirtazapine (sedating at low doses, less so at higher doses because of noradrenergic activation), trazodone as adjunctive at 25 to 150 mg at bedtime, doxepin at very low doses (3 to 6 mg is FDA-approved for insomnia and largely histaminergic at those levels). If the depression is the primary target and insomnia is a symptom, mirtazapine can cover both.

Avoid activating SSRIs at bedtime (fluoxetine, bupropion). Bupropion should generally be dosed in the morning; XL formulations tolerate an early afternoon dose but not evening.

Sleep hygiene, CBT-I, and treating any underlying OSA still matter. Medications work better when the sleep environment isn't fighting them.

Depression + sexual dysfunction concern

Bupropion is first-line when there's no significant anxiety component. It's the antidepressant most consistently associated with preserved sexual function. Vortioxetine has better sexual function data than SSRIs. Vilazodone similarly. Mirtazapine is generally well-tolerated on this axis.

Avoid SSRIs and SNRIs when sexual side effects are a leading concern. If an SSRI is otherwise the right choice, escitalopram tends to be more tolerable than paroxetine (which is often the worst offender), and adjunctive bupropion 150 to 300 mg XL can partially rescue sexual side effects.

Depression + weight concern

Bupropion is weight-neutral to weight-losing. Vortioxetine is weight-neutral in trials. Escitalopram is close to weight-neutral, especially in the short term.

Avoid mirtazapine (weight gain is substantial and reliable). Avoid paroxetine and TCAs (weight gain, more so than other SSRIs). SNRIs are variable: duloxetine tends to be neutral to mildly weight-losing early, venlafaxine similar.

If the patient is already overweight and metabolic risk is real: bupropion is the answer for most patients. Combined bupropion-naltrexone (Contrave) is an option when weight loss is a direct goal alongside depression.

Depression + anxiety

SSRIs first-line. Sertraline and escitalopram have the best combined evidence. Escitalopram is often preferred for tolerability. Sertraline has more anxiety-specific data (PTSD, panic, social anxiety indications).

Bupropion monotherapy can worsen anxiety in the first few weeks, so it's a poor choice when anxiety is prominent. If depression is dominant and anxiety is a secondary concern, bupropion can still work with slow titration; if anxiety is the dominant complaint, don't lead with bupropion.

Mirtazapine works well when both depression and anxiety are present, especially with insomnia in the mix. It's less commonly used first-line for anxiety alone.

Buspirone as adjunct for GAD component. Benzodiazepines for short-term bridging while an SSRI takes effect; not for chronic use.

Depression + fatigue

Bupropion. Sertraline at moderate doses (100 to 200 mg). SNRIs (duloxetine, venlafaxine, especially at doses over 150 mg where NE effects kick in). Adjunctive stimulant with caution and only in select cases (evidence is mixed; not first-line).

Avoid sedating options for a fatigued patient (mirtazapine, paroxetine). Also worth checking: sleep, iron, thyroid, B12, and depression severity itself. Antidepressant fatigue can be a discontinuation-worthy side effect, so it's worth distinguishing symptom from side effect.

Depression + chronic pain

Duloxetine is the mainstay. FDA-approved for MDD, GAD, diabetic peripheral neuropathy, fibromyalgia, chronic musculoskeletal pain. Venlafaxine at NE-active doses (over 150 mg) covers depression plus neuropathic pain. Amitriptyline at low doses (10 to 50 mg) for neuropathic pain with some antidepressant effect, though anticholinergic burden limits use in older adults. Milnacipran for fibromyalgia specifically.

Depression + migraine

Venlafaxine (limited migraine prevention evidence, but reasonable). Amitriptyline (established migraine preventive at 10 to 50 mg). Avoid MAOIs (dietary and drug interaction burden makes them impractical for someone on triptans, though pharmacologically the interactions with triptans matter).

Depression + hot flashes / perimenopause

Venlafaxine (75 mg XR, well-studied for hot flashes). Paroxetine (7.5 mg formulation approved for VMS; but avoid in tamoxifen users because paroxetine's 2D6 inhibition can compromise tamoxifen activation). Escitalopram (some data). Gabapentin (300 to 900 mg/day) as adjunct or alternative.

Depression + smoking

Bupropion does double duty. Approved as Zyban for smoking cessation, effective for depression at the same doses (150 to 300 mg XL). Combining with varenicline is reasonable in select cases.

Depression + ADHD

Both conditions matter, and treating one often improves the other. Options:

• Bupropion for both: reasonable evidence for ADHD (particularly in adults), works for depression, weight-neutral, minimal sexual side effects.
• SNRI plus stimulant: duloxetine or venlafaxine for depression, add a stimulant for ADHD. Compatible pharmacologically.
• Atomoxetine plus SSRI: watch 2D6 interactions if the SSRI is fluoxetine or paroxetine (both potent 2D6 inhibitors) because atomoxetine is a 2D6 substrate.
• Guanfacine adjunct: useful for ADHD, doesn't treat depression directly, can help with anxiety features.

Combining a stimulant with an SSRI or SNRI is generally safe. Watch cardiovascular status (blood pressure, pulse). Serotonin syndrome from stimulant plus SSRI is rare at therapeutic doses.

Bipolar disorder

Bipolar + anxiety

Lamotrigine (helpful for bipolar depression, doesn't directly treat anxiety but doesn't worsen it) plus a benzodiazepine bridge for acute anxiety. Quetiapine covers both bipolar mood symptoms and anxiety at moderate doses (150 to 300 mg). Lurasidone (bipolar depression, generally activating).

Avoid antidepressant monotherapy in bipolar patients. If an antidepressant is used, it should be with a mood stabilizer on board, and the choice matters: SSRIs generally, avoid TCAs and SNRIs where possible because of higher switch risk. Bupropion has a comparatively lower switch rate. Some clinicians avoid all antidepressants in bipolar I.

Bipolar + insomnia

Quetiapine low-dose (25 to 100 mg) is commonly used. Olanzapine works but has metabolic cost. Gabapentin 300 to 900 mg at bedtime. Ramelteon for chronic insomnia in patients where benzodiazepines are contraindicated.

Avoid z-drugs and benzodiazepines chronically. Short-term for acute crisis is fine; chronic use produces tolerance, dependence, and (in bipolar patients) potentially destabilizes mood.

Bipolar + ADHD

Stabilize mood first. Once mood is stable on lithium, valproate, lamotrigine, or an atypical, stimulants can be added carefully. Watch for hypomania induction. Some patients tolerate the combination well; some don't. Non-stimulant options (atomoxetine, guanfacine) have less mood-destabilizing potential and are reasonable first-line for ADHD in bipolar.

Psychosis paired

Psychosis + PTSD

Prazosin as adjunct for nightmares (1 to 15 mg at bedtime, titrate slowly). Quetiapine at moderate doses can help with both psychotic symptoms and sleep. Risperidone for both indications. For treatment-resistant PTSD-plus-psychosis, olanzapine or clozapine as considered.

Psychosis + substance use

Long-acting injectable antipsychotics improve adherence in patients with active substance use. Aripiprazole LAIs (Maintena, Aristada) preferred because of lower metabolic burden and less sedation. Contingency management, integrated dual-diagnosis treatment, and community support matter more than medication choice.

Psychosis + treatment-resistance

Clozapine remains the standard for treatment-resistant schizophrenia after two adequate antipsychotic trials. Nothing else has comparable efficacy in this population.

Anxiety spectrum paired

Panic disorder + comorbid substance use

SSRIs first-line (sertraline, escitalopram). Gabapentin adjunct as needed. Avoid benzodiazepines because of misuse and dependence risk in this population. CBT for panic is highly effective and worth prioritizing.

OCD + depression

OCD requires higher SSRI doses than depression. Fluoxetine to 80 mg, sertraline to 200 mg, fluvoxamine 150 to 300 mg, paroxetine 40 to 60 mg. Clomipramine remains highly effective and is reasonable when SSRIs fail. Augmentation with an atypical antipsychotic (aripiprazole, risperidone) has the best evidence for treatment-resistant OCD. CBT with exposure and response prevention is first-line even alongside medication.

GAD + depression

SSRIs (sertraline, escitalopram) or SNRIs (duloxetine, venlafaxine). Both categories cover both indications. Buspirone monotherapy for GAD without depression; adjunctive with an antidepressant if partial response.

Attention-deficit / hyperactivity

ADHD + anxiety

Guanfacine or atomoxetine as first-line non-stimulant options, or add a stimulant to an SSRI once the SSRI is well-tolerated. Some patients tolerate stimulants poorly when anxiety is prominent; others find that treating ADHD reduces anxiety driven by executive dysfunction. Individual response varies. SSRI plus stimulant is a common and well-tolerated combination.

ADHD + tics

Guanfacine or atomoxetine (guanfacine has some tic-suppressing effects). Stimulants can worsen tics but often are tolerated; if tics escalate on a stimulant, try a different stimulant class first (methylphenidate to amphetamine or vice versa) before switching to a non-stimulant.

The comorbidity matrix

Common questions

Best antidepressant for a patient with insomnia and weight concern? This one's a bind because the classic insomnia-friendly options (mirtazapine, TCAs) also drive weight gain. Reasonable approaches: bupropion in the morning plus a non-antidepressant sleep aid (low-dose doxepin 3 to 6 mg, ramelteon, trazodone 25 to 50 mg at bedtime); or vortioxetine plus a sleep aid; or an SSRI like escitalopram with sleep-focused CBT-I. Mirtazapine works spectacularly for sleep but you're accepting weight gain, and that trade-off should be an explicit conversation with the patient.

Bupropion in a patient with anxiety? Not first-line if anxiety is the dominant complaint. Bupropion's noradrenergic and dopaminergic effects can worsen anxiety in the first few weeks, and some patients don't get past that. If depression is the primary target and anxiety is mild, bupropion at 150 mg XL for a couple of weeks before increasing can work. If anxiety is significant, go with an SSRI first and reconsider bupropion later if sexual side effects or fatigue emerge on the SSRI.

Do I really need to avoid antidepressants in bipolar? Not absolutely, but the switch risk is real, and antidepressant monotherapy in bipolar I disorder is generally considered contraindicated. In bipolar II, the picture is less clear. The safer approach: mood stabilizer as the foundation, add antidepressant only if bipolar depression persists despite adequate mood stabilizer and evidence-based bipolar depression treatments (quetiapine, lurasidone, cariprazine, olanzapine-fluoxetine combination, lumateperone). If you use an antidepressant, an SSRI (not TCA, not SNRI) with a mood stabilizer on board, monitor for switch, and be willing to stop it.

SSRI for someone with chronic pain? SSRIs alone are weaker for pain than SNRIs or TCAs because the noradrenergic component matters for descending pain modulation. If the patient has both depression and chronic pain, duloxetine or venlafaxine at NE-active doses (over 150 mg) covers both. If they're on an SSRI already for depression and pain is secondary, options include adding a low-dose TCA (nortriptyline 10 to 25 mg) or switching to an SNRI.

Stimulant for ADHD if the patient has anxiety? Often fine. Anxiety driven by executive dysfunction (constant lateness, missed deadlines, perceived incompetence) frequently improves when ADHD is treated. Anxiety that's more general or panic-driven can be worsened by stimulants. Try methylphenidate class first (usually better tolerated than amphetamine class in anxious patients), start low, titrate slowly. If an SSRI is already on board for anxiety, adding a stimulant is compatible. Non-stimulant options (atomoxetine, guanfacine) are reasonable when stimulants exacerbate anxiety.

Sources

• NICE NG222: Depression in adults: treatment and management.
• American Psychiatric Association. Practice Guideline for the Treatment of Patients with Major Depressive Disorder, 3rd edition.
• CANMAT 2016 Clinical Guidelines for the Management of Adults with Major Depressive Disorder.
• Yatham LN, Kennedy SH, Parikh SV, et al. CANMAT and ISBD 2018 guidelines for the management of patients with bipolar disorder. Bipolar Disord. 2018;20(2):97-170.
• VA/DoD Clinical Practice Guideline for the Management of Posttraumatic Stress Disorder and Acute Stress Disorder. 2023.
• Cochrane reviews on antidepressants, mood stabilizers, and antipsychotics for specific indications.
• Wilens TE, Spencer TJ, Biederman J. A review of the pharmacotherapy of adults with attention-deficit/hyperactivity disorder. J Atten Disord.
• Stahl SM. Essential Psychopharmacology, 5th edition.
• Package inserts for referenced medications.

Reviewed against current guidelines as of June 8, 2026. This is not medical advice.