Medication

This page explains the main types of medication used for OCD and how they can reduce anxiety, based on current understanding.

However, before I start, I wish to put the disclaimer that I am not a medical professional. If you have any questions regarding medication, including whether you should take it or not, please see your doctor.

The medications used for OCD can be grouped by the balance they offer between anxiety reduction and possible side‑effects. This page outlines the main options, how they work, and what you can realistically expect from them.

SSRIs

The most common form of medications for OCD are selective serotonin reuptake inhibitors (SSRIs). These are considered the first‑line medication for OCD because they offer the best balance between anxiety reduction and possible side‑effects.

Well‑known SSRIs include fluoxetine (Prozac), sertraline (Zoloft), citalopram (Celexa), and paroxetine (Paxil).

In simple terms, SSRIs work by affecting serotonin in your brain. Serotonin is one of the chemicals that helps reduce anxiety.

There are two main explanations for how this serotonin effect helps with anxiety:

(1) Chemical Imbalance Theory

This theory claims that anxiety happens because the brain doesn’t have enough serotonin.

According to this view, SSRIs are believed to help by increasing the amount of serotonin available in the brain. The idea is that raising serotonin levels should reduce anxiety, because the anxiety is assumed to come from a deficiency.

There are two issues with this theory.

The first is that SSRIs don’t actually increase the amount of serotonin. SSRIs were created in the 1960s where there were no tools that could measure serotonin levels. Researchers noticed that some patients seemed calmer after taking them, and so assumed that the serotonin levels increased.

The second is that even if SSRIs did increase serotonin levels, this wouldn’t change anything. There are other medications that do increase the production of serotonin in the brain. But even these other medications are wholly ineffective in treating anxiety and depression.

The articles below discuss the problems with the chemical imbalance theory in more detail. Admittedly they concentrate more on depression than anxiety, but according to popular theory, both conditions stem from chemical imbalances, so what applies to depression can also apply to anxiety.

Guardian article
Psychology Today article

Therefore, increasing the amount of serotonin doesn’t reduce anxiety, which is why the chemical imbalance theory is increasingly seen as outdated.

So how do SSRIS reduce anxiety if not by increasing serotonin?

They do this by taking the existing amount of serotonin and keeping it out longer — a process called serotonin reuptake inhibition.

(2) Serotonin Reuptake Inhibition

Keeping serotonin out for longer matters for people with OCD because their brain cells need extra time with the existing serotonin to produce a proper calming effect.

To see how this process works, we need to briefly look at how serotonin moves between different cells in the brain.

There are two types of cells in the brain: one type sends out serotonin, and another type needs to receive it (for anxiety reduction). The sending cell can’t pass serotonin directly to the receiving cell. Instead, there’s a tiny space between them, and the sending cell releases serotonin into that space.

The receiving cell can only take the serotonin while it’s sitting in that space. But serotonin doesn’t stay there for long — if it isn’t picked up quickly, the sending cell pulls it back in.

For people who don’t have OCD, this short window is enough. Their receiving cells take in what they need before the serotonin disappears.

For people with OCD, this short window isn’t enough. Their receiving cells can’t take in the serotonin quickly enough, so they end up getting less than they need.

SSRIs help by keeping the serotonin in that space for longer, giving the receiving cells the extra time they need in people with OCD.

This longer time in the gap leads to reduced anxiety in two ways:

(a) Reduced Overall Tension
(b) Numbness Effect

(a) Reduced Overall Tension

OCD creates a lot of physical tension in the body. The constant intrusive thoughts make the muscles tighten, breathing feel heavier, and the chest feel pressured.

SSRIs help by gradually lowering this underlying physical tension. For most people, the change is noticeable — the body feels less tense, even if the tension isn’t fully gone.

When the body is less tense, intrusive thoughts and sensations feel less threatening because the body isn’t reacting to them as strongly. This effect is especially noticeable with OCD because the anxiety can be so intense.

When SSRIs do help, virtually all patients experience this reduction in physical tension.

(b) Numbness Effect

SSRIs, and some other medications, can create a numb or emotionally blunted feeling. Not everyone experiences this effect, and for many patients it does not appear at all.

This numbness effect doesn’t stop intrusive thoughts from appearing, but it reduces the emotional impact they have, leading to a noticeable drop in anxiety.

But this reduced anxiety comes at a cost — the same numbness that dulls fear and worry can also lessen positive emotions, making everyday experiences such as eating food less enjoyable.

I’ll explain the numbness effect in more detail by looking at how it appears across two Dose Durations — Partial Day Effect and Full Day Effect.

Partial Day Effect

For some patients, the numbing sensation lasts only part of the day. The medication produces a numbing sensation that typically lasts around 8 to 12 hours after each dose. For example, if a patient takes the medication at 9am, the numbing effect may continue until roughly 9pm the same day. After that point, as the sedative impact wears off, the protective effect disappears, and the OCD symptoms return to their usual intensity.

Even though this partial day sedation is often described as a side-effect, for some patients it is actually the mechanism that makes the medication helpful, because during those hours the anxiety response is reduced.

However, the same numbing can also dampen positive emotions, making everyday pleasures like food less enjoyable.

Full Day Effect

For other patients, the numbing sensation extends across the entire day. This provides continuous reduction of anxiety, rather than limiting relief to an 8–12 hour window.

Another advantage of the full day effect is that, for some patients, the same dose provides stronger anxiety relief than the partial day effect during the 8–12 hour window.

The trade off is that while this stronger and more persistent numbing provides greater anxiety relief, it also dulls positive experiences more than the partial day effect.

And just like the partial day effect, this continuous numbness is often described as a side-effect, yet for certain patients it is the very reason the medication is effective, because it consistently reduces the anxiety.

To ease the dulling of positive experiences caused by numbness, short term therapy such as CBT can help reduce OCD anxiety within 3 to 12 months. Thus, patients may be able to lower their medication dose, lessening the numbness and regaining enjoyment of everyday activities. In some cases, therapy may reduce the anxiety enough for you to stop your medication altogether, and manage any remaining anxiety using techniques learned in therapy. Always speak to your doctor before reducing or stopping any medication.

My Personal Experience

I took SSRIs, and they did help me. In particular, they made my brain feel numb, which meant each OCD thought registered as less threatening. As a result, the anxiety these thoughts normally triggered was reduced.

This experience reflects what I described earlier as the numbness effect. The medication did not stop the intrusive thoughts themselves — they still appeared in my mind — but the emotional impact was blunted/reduced.

Importantly, this numbness did not mean I lost the ability to think clearly or function in daily life. I could still use my intellect at work and remain fully aware in situations that required attention, such as crossing busy roads.

If your anxiety is severe enough, you should seriously consider taking them. When they work, they can reduce the anxiety significantly.

SSRIs do have drawbacks, in the form of side effects. When people first start taking them, it is possible to get side effects such as diarrhoea, headaches, feeling disorientated, or an increase in anxiety. Not everyone experiences these, and for those who do, they usually go away after around two weeks.

These side-effects occur because the serotonin stays active for longer than the body is used to, which creates a brief chemical shock.

Alongside these short‑term physical effects, some people also notice emotional changes, in particular numbness.

Numbness can appear when starting SSRIs. If this numbness disappears after the first couple of weeks, then it is simply a temporary side-effect. However, if the numbness continues beyond that period, it is not a side-effect — it is the very mechanism by which the medication reduces anxiety. For more detail, refer back to the Numbness Effect section.

Clomipramine

Clomipramine is considered a second‑line medication for OCD.

It reduces OCD symptoms more strongly than SSRIs but it also causes more side-effects, which is why it’s usually tried only after SSRIs haven’t helped enough.

Clomipramine works in three ways:

First, Clomipramine keeps the chemical serotonin active for longer. This serotonin effect is generally stronger than with SSRIs, therefore anxiety is often reduced more than with SSRIs.

Second, Clomipramine also keeps the chemical noradrenaline active for longer. This is another way in which the medication may help reduce anxiety.

Third, Clomipramine can produce a numbing effect in some patients. This can make intrusive thoughts feel less threatening, which may further reduce anxiety.

Other Medications

If you are not prepared to take SSRIs or Clomipramine due to their side-effects, there are two more medications that you can try.

These are Pregabalin and Propranolol. They both tend to have fewer side-effects compared to SSRIs and Clomipramine, though for many people the reduction in OCD anxiety is also less. I took Propranolol first, and the reduction in anxiety was around 2%. I stopped taking that and then tried Pregabalin, and the anxiety was reduced by around 3% to 4%. These medications did not help me significantly enough when I was taking them, so I ended up taking SSRIs. But it could be different for you.

Short-Term Sedative Medications

When OCD first appears, the anxiety can be so overwhelming that doctors sometimes prescribe short-term sedative medications, such as Benzodiazepines. These provide almost immediate relief, and for some people, the medication is so effective that the anxiety from the intrusive thoughts goes completely.

Their calming effect often lasts somewhere in the range of 6 to 10 hours, depending on the specific medication and dose. However, they are strictly a temporary measure — usually prescribed for only a few days or weeks. This is because they can be highly addictive, and the medication often loses its effectiveness after two to four weeks. They serve as an "emergency bridge" to help you stabilize while waiting for long-term medications such as SSRIs to kick in, or for therapy to begin working.

Intrusive Thoughts and Medication

A common concern people have when taking antidepressants is whether they can cause intrusive thoughts.

No. They don’t create intrusive thoughts. OCD intrusive thoughts appear when the body is overwhelmed, mainly by stress or trauma.

Medication doesn’t add any new OCD thoughts. But in the first couple of weeks, antidepressants can briefly increase overall tension in the body, which can make existing OCD thoughts feel more intense. This settles as your body adjusts.

So medication doesn’t increase intrusive thoughts — in fact, for many people it reduces the number of thoughts. It also often makes the thoughts feel less intense. Together, these changes can noticeably lower daily anxiety.

Conclusion

Medication is best seen as a support tool. It can lower overall anxiety enough to make daily life and therapy easier — but it doesn’t address the root cause of OCD. That deeper change comes from addressing the life events that led to OCD in the first place.

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