Key points
- SSRI stands for selective serotonin reuptake inhibitor, a type of antidepressant also used for some anxiety disorders.
- Labels describe the action on serotonin, but do not explain every step of how anxiety eases.
- Benefits build over weeks, and NIMH says early side effects are usually not severe for most people.
- MedlinePlus says to keep taking these medicines even when you feel well, and not to stop without talking to your doctor.
- A boxed warning covers suicidal thoughts and behavior in children, teens and young adults.
What an SSRI does in the brain
Nerve cells pass signals using chemicals such as serotonin. After a signal is sent, serotonin is taken back up into the nerve cell. An SSRI blocks that reuptake. The sertraline (Zoloft) label says it strengthens serotonin activity in the central nervous system by inhibiting the reuptake of serotonin.
The word "thought" matters here. The escitalopram (Lexapro) label says the way it works against depression is presumed to be linked to this serotonin effect, so even the label describes a likely explanation and not a complete one. The labels do not explain why benefits build over weeks.
Which anxiety conditions SSRIs are labeled for
FDA labels are specific to each medicine. An SSRI approved for one condition is not automatically approved for another.
- Sertraline (Zoloft): the label lists panic disorder and social anxiety disorder, along with major depressive disorder, obsessive-compulsive disorder, posttraumatic stress disorder and premenstrual dysphoric disorder. Generalized anxiety disorder is not on this label.
- Escitalopram (Lexapro): the label lists generalized anxiety disorder in adults and in children 7 and older, and major depressive disorder in adults and children 12 and older.
What the first weeks are generally like
SSRIs are not fast-acting. NIMH says they may take several weeks to start working for generalized anxiety disorder, and MedlinePlus says it may take a few weeks or longer to feel the full benefit of sertraline and several weeks for escitalopram. This gap can feel discouraging, especially when anxiety is what brought you in. It can help to know this waiting period is expected.
Side effects can show up before benefits do. NIMH lists headaches, nausea and difficulty sleeping, and says these are usually not severe for most people, especially when the dose starts low and increases slowly. Your prescriber sets your plan, so please do not change it yourself.
The most common side effects on the labels vary by medicine. For sertraline they include nausea, diarrhea, tremor, indigestion, decreased appetite, heavy sweating, ejaculation problems and decreased sex drive. For escitalopram they include insomnia, nausea, sweating, fatigue, sleepiness, ejaculation problems, decreased sex drive and difficulty reaching orgasm. Sexual side effects can feel awkward to mention, but they are a normal thing to raise.
Worth telling your prescriber about
- Worsening mood, agitation or any thoughts of suicide.
- Every other medicine and supplement you take, especially triptans or St. John's wort, which NIMH says can contribute to serotonin syndrome.
- Whether you are pregnant, planning a pregnancy or breastfeeding.
- Anything that makes it hard to keep taking the medicine as prescribed.
Why SSRIs are not taken as needed
Some anxiety medicines can be used only when symptoms flare. NIMH describes benzodiazepines and beta-blockers as useful as needed for severe short-term anxiety. SSRIs are different. MedlinePlus says to take sertraline and escitalopram at around the same time every day, and to continue even if you feel well.
In other words, an SSRI is a regular daily plan, not something you reach for during a hard moment. The benefit described in these sources builds with steady use over weeks. Skipping doses or taking one only on stressful days is not how the medicines are directed to be used.
Important warnings
Boxed warning: antidepressants, including SSRIs, increased the risk of suicidal thoughts and behavior in children, teens and young adults in short-term studies. People of any age taking them should be watched closely for worsening or for suicidal thoughts, especially in the first few weeks and when the dose changes. If you are in crisis, call or text 988, or call 911. Locascio Wellness does not provide emergency services.
These labels say SSRIs must not be combined with MAOIs, an older type of antidepressant, or used within 14 days of them, because of the risk of serotonin syndrome. NIMH describes this as rare but life-threatening, with symptoms such as agitation, muscle twitches, hallucinations, high temperature and unusual blood pressure changes. The labels also warn about a higher risk of bleeding with aspirin, NSAIDs and blood thinners.
Do not stop an SSRI suddenly. MedlinePlus says sudden stopping can cause withdrawal symptoms such as nausea and sweating, and the labels recommend reducing the dose gradually whenever possible. Your prescriber can plan that with you.
Getting support
You can learn more about individual medicines on our pages for sertraline and escitalopram. See also our overview of online anxiety treatment.
A licensed psychiatrist on our team treats anxiety by secure video for people physically located in Pennsylvania or New York during each visit. Whether an SSRI is an option for you is a decision for you and your prescriber. Ask us whether our psychiatrist can help: contact us about medication care. Our therapists do not prescribe, and they see clients in Pennsylvania, West Virginia, Arizona, Colorado and Florida, not New York.
Common questions
How long does an SSRI take to work for anxiety?
It varies. NIMH says antidepressants usually take 4 to 8 weeks to work, and that they may take several weeks to start helping generalized anxiety. MedlinePlus says it may take several weeks or longer to feel the full benefit. Your prescriber can tell you what to watch for and when you will check in.
Can an SSRI make anxiety feel worse at first?
Tell your prescriber if anxiety, agitation or restlessness shows up or increases after you begin. The labels ask for close monitoring for clinical worsening, and sudden changes in mood or behavior should be reported right away. If you have any thoughts of harming yourself, call or text 988, or call 911.
Are SSRIs addictive?
The sertraline and escitalopram labels do not list them as controlled substances, but that does not mean stopping is simple. MedlinePlus says stopping suddenly can cause withdrawal symptoms, and the labels recommend reducing the dose gradually whenever possible. That is why any change should be planned with your prescriber and not done alone.
Do I also need therapy if I take an SSRI?
NIMH says medications are often used in combination with other treatments, such as psychotherapy, and that treatment plans depend on a person's needs and medical situation. Ask us whether therapy here makes sense for you. Our therapists see clients in five states, not New York, so a reader in New York would look for a therapist elsewhere.
Sources
Published by Locascio Wellness. Published November 5, 2026. Clinically reviewed by Kenneth M. Levy, DO, Psychiatrist (Pennsylvania license OS007464L). This page is general information, not medical advice or a diagnosis.