Mirtazapine For Anxiety: All You Need To Know

Generalized anxiety disorder (GAD) is a common condition that affects 3.1% of the US population¹. Up to one in five adults² (20%) suffer from an anxiety disorder. 

Women are more likely³ than men to be affected by anxiety. One study⁴ found that the chances of developing any type of anxiety disorder over a lifetime are 30.5% for women and 19.2% for men. 

A report by the World Health Organization (WHO)⁵ in 2017 found that anxiety was the sixth most common disorder causing significant disability in people’s lives in highly developed countries. 

If you struggle with anxiety, you may be prescribed mirtazapine (brand name Remeron) to help control your symptoms. Learn below all you need to know about anxiety, how mirtazapine helps, how long it might take to start working, and what side effects or special precautions you need to be aware of. 

Have you considered clinical trials for Anxiety?

We make it easy for you to participate in a clinical trial for Anxiety, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

What is an anxiety disorder?

Experiencing occasional anxiety is normal, but when your symptoms start to interfere with your daily functioning, you may have an anxiety disorder. 

Some symptoms that you may experience if you have an anxiety disorder are:

According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V), to be diagnosed formally with an anxiety disorder, you must meet the following criteria:

  • Your symptoms must have been present for at least six months

  • Your symptoms must result in significant distress or impairment in social and/or occupational functioning

  • The symptoms must not be attributable to a physical cause, such as an overactive thyroid 

If you struggle with an anxiety disorder, you may find that you have excessive and persistent worry or fear about everyday situations. You may also have repeated episodes of intense fear and anxiety (panic attacks) that may be so severe it can feel as though you are having a heart attack. 

You may find that you start adapting your lifestyle to avoid situations or activities that trigger anxiety.

Symptoms of an anxiety disorder often start in childhood or adolescence⁶ and continue into adulthood. 

Different types of anxiety disorders

Not all anxiety is the same. Anxiety can be differentiated into various specific disorders. 

Take a look at the classification below to help you identify which type of anxiety disorder you most likely suffer from. This is important because some treatments work better for specific types of anxiety

Generalized anxiety disorder

  • Persistent, excessive worry about routine events or situations

  • Disproportionate worry that is difficult to control

  • Your anxiety impacts your ability to function


  • Fear of being in places or situations that may cause you to feel trapped, helpless, or embarrassed 

  • Avoidance of situations or places that cause you to feel trapped, helpless, or embarrassed

  • In severe cases, you may feel too afraid even to leave home

Panic disorder

  • Repeated episodes of intense fear, worry, or terror that reach a peak within a few minutes

  • Associated with physical symptoms, such as shaking, shortness of breath, sweating, nausea, and heart palpitations

  • Physical symptoms can be so severe that you believe you are having a heart attack or are about to die

  • You may develop a fear of having future panic attacks

Anxiety disorder caused by a medical condition

This type of anxiety can be triggered by an underlying medical condition, such as an overactive thyroid. Usually, you would have symptoms of anxiety as well as of the underlying medical condition.

Social anxiety disorder

  • High levels of anxiety or fear related to being in social situations

  • Feeling abnormally self-conscious in the company of others

  • May lead to avoidance of social situations

  • Disproportionate fear or concern about being judged negatively by others

Specific phobias

  • Major anxiety on being exposed to a certain trigger or situation

  • Avoidance of your specific trigger

  • You may experience panic attacks in response to your trigger

Childhood anxiety disorders

These include childhood anxiety disorders such as separation anxiety and selective mutism.

  • Present in childhood

  • May sometimes continue into adulthood

  • Interfere with school and/or social functioning

Substance-induced anxiety disorders

These are intense feelings of anxiety or panic related to taking or misusing certain drugs or medications.

Causes of anxiety disorders

The exact cause of anxiety is not fully known. It is likely that anxiety disorders are caused by a combination of factors, including both your genes and your environment.

Genetics are known to play a role in the development of anxiety disorders. You are more likely to develop an anxiety disorder if you have a blood relative who suffers from it.

There is evidence to suggest that an imbalance in the neurotransmitters² in your brain may play a role in the development of anxiety disorders. People with low serotonin activity and elevated noradrenergic system activity may be more prone to developing anxiety.  

The following factors have been identified as putting you at greater risk of developing an anxiety disorder:

  • Trauma

  • Stress as a result of ill health

  • Excessive or persistent life stressors

  • Some personality types may be more prone to developing anxiety disorders

  • Drug or alcohol use or misuse

  • Other mental health disorders, such as depression or substance abuse

Treatment of anxiety

The mainstay of treatment for anxiety disorders is medication in conjunction with psychotherapy, such as cognitive behavior therapy. Lifestyle modifications, including exercise and mindfulness practice, can also be effective as part of your treatment regimen.

Mirtazapine may be one of the medications prescribed to treat your anxiety. If you have been prescribed mirtazapine, you may want to find out more about how it helps treat anxiety, how long it takes to work, how you should take it, and what you need to be aware of when taking it. 

What is mirtazapine?

Mirtazapine⁷ is the active ingredient in a drug called Remeron, and it belongs to a class of medication called tetracyclic antidepressants. Although mirtazapine is an antidepressant, it is also used to treat anxiety, especially for generalized anxiety disorder⁸. 

Neurotransmitters are chemicals in the brain that jump between brain cells (neurons) to relay messages and alter the function of the neurons. The main neurotransmitters associated with anxiety disorders are serotonin and noradrenaline. 

There is some evidence that people with low serotonin activity and elevated noradrenergic system activity may be more prone to developing anxiety. 

How does mirtazapine work?

Mirtazapine acts by blocking the alpha-2 receptor⁹, which results in increased levels of serotonin and noradrenaline in the ends, or synapses, of brain cells. 

Mirtazapine is not usually used as a first-line therapy for anxiety. First-line therapy for anxiety is normally selective serotonin reuptake inhibitors (SSRIs) or serotonin noradrenaline reuptake inhibitors (SNRIs). However, if you have very symptomatic anxiety, your doctor may decide to start you on mirtazapine. 

The reason for this is that, unlike the SSRIs and SNRIs, mirtazapine doesn’t aggravate your anxiety symptoms. Because it has a sedating effect, it can be helpful if your anxiety is so bad you can’t risk having to tolerate an initial exacerbation. 

Mirtazapine may also be the treatment of choice for you if you are struggling with insomnia due to your anxiety. Its sedating effect can help you get a good night’s sleep. 

How do you take mirtazapine?

Mirtazapine is available in two formulations¹⁰, a tablet form and a soluble form (dispersible tablet). The starting dose for mirtazapine is usually 15mg, which may be increased up to 30mg and then 45mg until the dose is enough to control your anxiety.

Mirtazapine should always be taken in the evening before bed because of its sedating effect. 

How long does mirtazapine take to have an effect?

Although mirtazapine is sedating and will help you have a good night’s sleep straight away, you will only feel the full anxiety-reducing and calming effects of the medication after four to six weeks⁷.

Side effects of mirtazapine

As with any medication, there are potential side effects that you may experience when taking mirtazapine. Some of the common side effects¹¹ include:

  • Sleepiness and drowsiness, including residual morning sedation

  • Weight gain

  • Increased appetite

  • Dry mouth

  • Constipation

  • Feeling faint

Many of these side effects will diminish as your body gets used to taking the medication. 

You can have more severe, rare side-effects to mirtazapine¹². These are uncommon, but if you experience them, you should contact your doctor immediately. 

Many of them will diminish as your body becomes accustomed to the medication. To minimize the side effects, your doctor will likely start you on a low dose and titrate up as your body adjusts to the mirtazapine. 

Serotonin syndrome

Serotonin syndrome¹³ is a rare but potentially life-threatening condition characterized by excessive sweating, shivering, incoordination, muscle spasms, and altered levels of consciousness. 

You may be more likely to experience this side effect if you take mirtazapine in conjunction with other medications that cause an increase in serotonin levels, such as medication for Parkinson’s disease, migraine headaches, or herbal antidepressants, such as St. John’s Wort. 

Low white blood cell count

You may not know that your white blood cell count has dropped, but you may experience flu-like symptoms, fevers, chills, sore throat, and sores in your mouth and/or nose.

Low blood salt levels

Mirtazapine may also cause the salt levels in your blood to drop. This can lead to headaches, confusion, decreased level of consciousness, slurred speech, weakness, and feeling unsteady. 

When should you not take mirtazapine?

Mirtazapine may not be suitable for all people. You should not take mirtazapine⁷ if you have any of the following conditions:

  • Have low blood pressure

  • Have glaucoma (raised pressure in your eyes)

  • Have epilepsy or seizures

  • Are pregnant, or are trying to become pregnant

You should also take care if you have diabetes, as mirtazapine can make it more difficult to keep your blood sugar levels stable. 

You should avoid drinking alcohol if you take mirtazapine as it can exacerbate the sedating effects. 

How and when to stop mirtazapine

Although you may start feeling as though your anxiety is improving after four to six weeks of taking mirtazapine, your doctor will most likely recommend that you continue with the medication for at least six to twelve months⁶. This is to minimize the risk of having a relapse. 

When you are ready to stop taking mirtazapine, you should not stop it cold turkey as this can lead to discontinuation of side effects¹². When you are ready to stop taking mirtazapine, discuss the best way to stop with your doctor. 

The lowdown

Mirtazapine works by increasing serotonin and noradrenaline levels in the ends of your neurons. It takes between four and six weeks to take full effect, although it causes sedation immediately. This can be beneficial if you are struggling to sleep due to your anxiety. 

Mirtazapine should be taken at night before bed and should not be taken with alcohol because of its significant sedating effect. 

Unlike the SSRIs and SNRIs, mirtazapine does not initially cause a worsening of anxiety symptoms. Because of this, if your anxiety is very debilitating, your doctor may recommend mirtazapine.

Have you considered clinical trials for Anxiety?

We make it easy for you to participate in a clinical trial for Anxiety, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

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