What Are SSRIs? How Antidepressants Work, and Can You Float While Taking Them?

Updated: 12 October 2026 · Compiled by Float Vietnam

This article is general information and does not replace advice from your doctor. Never stop, reduce or switch medication on your own; any change should be guided by your doctor.

Quick answer: SSRIs are antidepressants that block the serotonin “recycling pump” on nerve cells, prescribed for depression, anxiety and OCD. In Vietnam, antidepressants are prescription-only. If you are on a stable dose of an SSRI, floating is usually compatible: in the 2018 Laureate Institute study, 40% of participants were taking an SSRI or SNRI, and anxiety fell just as much whether or not they were medicated. Ask your doctor first, especially when starting, changing dose or tapering.

What is an SSRI and how does it work?

Think of serotonin as a message sent across the gap between two nerve cells. After sending it, the cell takes the message back with a pump. SSRIs block that pump, so serotonin stays in the gap longer. That happens within hours, but mood usually improves only after 2–6 weeks; scientists think the benefit comes from slower adaptations in the brain, such as receptor changes and how emotions are processed, rather than simply “topping up” serotonin.

Drug	Original brand	Notes
Fluoxetine	Prozac	The first SSRI in the US; very long half-life
Sertraline	Zoloft	Very widely used
Escitalopram	Lexapro, Cipralex	Scored well on effectiveness and tolerability in the 2018 analysis
Paroxetine	Paxil, Seroxat	Short half-life; stopping symptoms are more common
Citalopram	Celexa, Cipramil	Dose limits in older adults because of effects on heart rhythm
Fluvoxamine	Luvox, Faverin	Often used for OCD; many drug interactions

Other groups: SNRIs (venlafaxine, duloxetine) block the recycling of both serotonin and noradrenaline; tricyclics (such as amitriptyline) are older with more side effects, including dry mouth, dizziness on standing and reduced sweating; MAOIs need some food restrictions and are combined with SSRIs only under specialist care. In Vietnam, antidepressants are prescription-only.

A short history: from a TB drug to the “Prozac era”

Year	Milestone
1951–1957	Iproniazid, a tuberculosis drug, was seen to lift patients’ mood; by 1957 it and imipramine became the first antidepressants (MAOI and tricyclic)
1965	Joseph Schildkraut proposes the catecholamine hypothesis, a forerunner of the monoamine theory
1972–1974	At Eli Lilly, Bryan Molloy, David Wong and Ray Fuller find a compound that selectively blocks serotonin reuptake, later named fluoxetine
29 Dec 1987	The FDA approves Prozac for depression
1993–1994	Peter Kramer’s Listening to Prozac and Elizabeth Wurtzel’s Prozac Nation turn Prozac into a cultural symbol
2004, 2007	The FDA requires a boxed warning on suicidal thoughts in children and teenagers, later extended to ages 18–24
2018	Cipriani et al. analyse data from 116,477 people: all 21 antidepressants beat placebo
2022	A review by Moncrieff et al. finds no consistent evidence that depression is caused by “low serotonin”, sparking a major debate

Do they work? Understanding the serotonin debate

The largest analysis so far (Cipriani 2018, The Lancet, 522 trials) found all 21 antidepressants worked better than placebo over the first 8 weeks in adults with major depression. The average difference from placebo is moderate and clearer in moderate to severe depression; averages also hide people who benefit a lot. UK NICE guidance (2022) says that for less severe depression, medication should not be the automatic first choice, with talking therapy and exercise offered first unless the person prefers medication.

In 2022, a review by Moncrieff and colleagues found no consistent evidence that depression is caused by “low serotonin”. Critics (Jauhar 2023) replied that the serotonin system is still involved, even if the “chemical imbalance” story is too simple. The key point: that review was about what causes depression, not whether the medicines work. Many good medicines work in ways different from their original theory.

Side effects and stopping

• Common: nausea, headache, sleep changes, dizziness, drowsiness, heavy sweating, lower sex drive; many ease after 1–2 weeks.
• Emotional blunting: in one survey close to half of people on antidepressants reported it, although depression itself may play a part.
• Discontinuation symptoms: dizziness, “brain zaps”, irritability and poor sleep. A 2024 analysis of over 21,000 people estimated that about 15% have symptoms caused by stopping itself, and about 3% have severe ones. So never stop suddenly; tapering should be slow and supervised by a doctor.
• Persistent sexual dysfunction after stopping (PSSD): added to European product information in 2019; how often it happens is unknown.
• Under 25s: need close monitoring in the first 1–2 months because of a small rise in suicidal thoughts.

What not to combine with SSRIs

Serotonin syndrome is rare but can be dangerous, with signs such as agitation, heavy sweating, fever, tremor, muscle twitching, a fast heartbeat and diarrhoea. If you notice them, seek emergency care. The risk is higher when SSRIs are combined with St John’s wort, the painkiller tramadol, triptan migraine drugs, ecstasy (MDMA) and some other medicines. Alcohol adds to dizziness and drowsiness and can worsen mood. Always tell your doctor or pharmacist about every medicine and supplement you take. On psilocybin and other psychedelics, see what are psychedelics.

Can you float while taking an SSRI?

No study has been designed specifically to test SSRIs plus floating, but major float studies have included people on stable medication:

• Feinstein 2018 (Laureate Institute, 50 people with anxiety): anyone on medication had to be on a stable dose for at least 6 weeks; 40% were on an SSRI or SNRI. Anxiety fell sharply after one float, equally with or without medication, and there were no serious adverse events.
• Garland 2024 (randomised trial, 75 people with anxiety or depression, 6 floats): stable medication for at least 8 weeks was allowed; no serious adverse events related to floating.
• Jonsson and Kjellgren 2016 (generalised anxiety): participants continued their existing care; about 40% were on anti-anxiety or antidepressant medication.

Float water is about 35°C, close to skin temperature and far gentler than a sauna. A few points are still useful: SSRIs can cause heavy sweating and, rarely, low blood sodium, especially in older women, so drink normally rather than excessively. Lying still in warm water for 60–90 minutes and then standing up quickly can make you light-headed, so sit for a moment first.

Checklist before a float:

• Your dose is stable; if you have just started, changed dose or are tapering, ask your doctor and consider waiting.
• Tell your doctor and the float centre staff that you take medication.
• Take your medicine as prescribed; do not skip or delay a dose for a float.
• Skip the float if you feel dizzy, faint, feverish or confused; you can leave the pool at any time.
• Stand up slowly after the session.
• Drink water normally before and after.
• No alcohol or recreational drugs before a float.
• Be careful about combining sauna and floating on the same day if your medicine makes you sweat heavily or you are older.

Check first if you have uncontrolled epilepsy, open wounds, active psychosis or mania, thoughts of self-harm (seek help first) or are pregnant. See also is float therapy safe.

Alongside care, not instead of it

Several non-drug approaches have good evidence and can sit alongside medication: talking therapies such as CBT; exercise (a 2024 analysis of 218 trials found walking, jogging, yoga and strength training reduced depression); mindfulness-based cognitive therapy (about 31% lower relapse risk over 60 weeks); and regular sleep. Floating is one restful tool among these: early studies show clear short-term drops in anxiety and low mood. None of them is a reason to stop medication on your own. Read more on the Laureate Institute float studies and float therapy for insomnia.

Getting help in Vietnam

• Emergency: 115, or go to the nearest emergency department if someone is in danger.
• Ngày Mai helpline: 096 306 1414, free listening and emotional support for people with depression and their families (Vietnamese and English).
• For medication questions, see a psychiatrist at a psychiatric hospital or the psychiatry department of a major hospital.

Key sources

• Cipriani et al. 2018, Lancet
• Kirsch et al. 2008, PLoS Medicine
• Moncrieff et al. 2023, Molecular Psychiatry
• Jauhar et al. 2023, Molecular Psychiatry
• Henssler et al. 2024, Lancet Psychiatry
• Horowitz & Taylor 2019, Lancet Psychiatry
• Feinstein et al. 2018, PLOS ONE
• Garland et al. 2024, PLOS ONE
• Jonsson & Kjellgren 2016, BMC Complement Altern Med
• Noetel et al. 2024, BMJ
• Kuyken et al. 2016, JAMA Psychiatry

For newer approaches being studied in hard-to-treat depression, read ketamine and psilocybin for depression.

Note: This page is for general information. Float therapy supports wellbeing but does not replace diagnosis or treatment by a doctor. If you have a medical condition, ask your doctor before floating.

Try it at Ōmni Space. Float Vietnam’s float rooms are at 16C Quoc Huong, Thao Dien, Ho Chi Minh City (Saigon), open daily 9:00–21:00. Book a float or read the float therapy FAQ.