Antidepressants for Anxiety

What is anxiety?

To define anxiety it is important to first define ‘fear’.

What is fear? Fear is a strong emotion that occurs when you are faced with a situation that is deemed as ‘dangerous’, and this triggers your fight or flight response.¹

Anxiety produces a feeling of fear, worry and a feeling of being overwhelmed. These feelings are excessive, and involve unrealistic worrying about everyday things in your life.²

Prevalence of anxiety disorders

Anxiety disorders are the most common psychiatric disorder. Generalised anxiety disorder is the most common in high income countries, with an estimation that 7.8% of the US population will have generalised anxiety disorder at some point in their lifetime. In Europe, the statistic is more variable with 1-7% of individuals expected to suffer at some point in their life.

Importance of treatment

Treatment options for anxiety vary from therapy to medication. Therapy can help you to manage your anxiety symptoms, and reduce the intensity of these symptoms. Similarly, medications such as antidepressants can help to lessen your symptoms of anxiety, leaving a sense of calmness.

Understanding antidepressants

Overview of antidepressant medications

Antidepressants are not just limited to treating depression, as the name might suggest, but also generalised anxiety disorder.³

Antidepressant classes for anxiety

Antidepressant classes for anxiety include the following:

• Selective serotonin reuptake inhibitors (SSRIs)
• Serotonin-noradrenaline reuptake inhibitors (SNRIs)
• Atypical antidepressants

The above classes of antidepressants for anxiety will be discussed in more detail below.

SSRIs

The first class of antidepressant drugs is SSRIs. The following SSRIs are used to treat anxiety:

• Paroxetine (Paxil)
• Sertraline (Lustral)
• Escitalopram (Cipralex)

To understand how SSRIs work, it is important to understand what serotonin is. Serotonin is a chemical messenger that aids in carrying signals between different nerve cells in your brain. Serotonin is believed to have a positive influence on your mood. After serotonin has been released by your nerve cells and used to carry a message, it is reabsorbed by your nerve cells. 

However, SSRIs block the serotonin transporter, which reabsorbs serotonin back into your nerve cells, meaning that more serotonin is available. This allows more signals to be passed between your nerve cells. However, it is important to note that it is too simplistic to state that anxiety disorders are a result of low serotonin levels in the brain, but evidence has shown that increased serotonin levels in your brain can help with relieving symptoms of anxiety.⁴ 

SNRIs 

The way in which SNRIs work is similar to that of SSRIs, but they prevent the reabsorption of two chemical messengers in the brain, which are serotonin and noradrenaline. This affects the communication between the nerve cells which control your mood, and this in turn can aid in relieving your symptoms of anxiety.

You may be prescribed one of the following SNRIs for anxiety:

• Venlafaxine
• Duloxetine

Atypical antidepressants

If SSRIs and SNRIs are not an appropriate antidepressant drug for you, you may be prescribed an atypical antidepressant. Atypical antidepressants for treating anxiety include the following:

• Bupropion: this prevents the reabsorption of two chemical messengers, which are used to send signals between nerve cells in your brain. The chemical messengers are noradrenaline and dopamine⁵
• Mirtazapine: this also acts on the chemical messengers in your brain, and increases the levels of both noradrenaline and serotonin in your brain
• Agomelatine: this activates the melatonin receptor, which helps to keep your anxiety at bay⁶

Role of neurotransmitters in anxiety

Serotonin

Anxiety has been linked to less serotonin, and less serotonergic activity in your brain. A study found that low levels of serotonin were associated with anxiety. However, after patients were given an anxiety disorder medication, such as SSRIs, their serotonin levels increased to a normal level, and the individuals experienced no anxiety.⁷

Noradrenaline

Noradrenaline is another neurotransmitter associated with anxiety. However, the exact dynamics of noradrenaline’s role in anxiety disorders remains unclear.⁸

Side effects of antidepressant medications for anxiety

SSRI and SNRIs

You may experience some of the following common side effects if you are prescribed SSRIs or SNRIs as an antidepressant medication:

• Dizziness
• Nausea
• Sexual problems, such as low libido which results in a low sex drive or erectile dysfunction
• Headaches
• Indigestion
• Constipation
• Blurred vision
• Insomnia
• Drowsiness
• Having a dry mouth
• Excessive sweating
• Agitation
• Vomiting

Less common side effects of SSRIs

Less common side effects of SSRIs may also be observed, and these can include the following:

• Confusion
• Movement problems
• Bleeding easily, including vomiting blood
• Bruising easily
• Hallucinations
• Hyponatraemia: where elderly people who take SSRIs experience a fall in their sodium levels. Hyponatraemia can be mild or severe
• Being unable to urinate when you go to the toilet
• Suicidal thoughts, this may also occur if you are taking SNRIs. emergency assistance
• Serotonin syndrome: where the levels of serotonin in your brain are too high. This can cause agitation, shivering, sweating, muscle twitches, an irregular heartbeat, a temperature above 38 C, seizures and a loss of consciousness. Please note that serotonin syndrome may also occur due to SNRI use. 

If you experience any of the above symptoms you should seek advice from a medical professional immediately or call 111. Severe serotonin syndrome and hyponatraemia are very serious and you should call 999 and request an ambulance if these symptoms are observed.

Side effects of atypical antidepressants

Moving on from the side effects of SSRIs and SNRIs, what are the most common side effects from atypical antidepressants?

Beginning with bupropion, the following are some of the common side effects this anxiety medication can cause:

• Hyperventilation
• Having a dry mouth
• Irregular heart beat
• Feeling restless/irritable
• Having trouble sleeping

Less common side effects from taking bupropion include the following:

• Confusion
• Fainting
• Skin rash and itching
• Ringing in your ears
• Seizures
• Feeling exceptionally distrusting towards others
• Trouble concentrating

Mirtazapine can cause the following side effects:

• Feeling tired
• Nausea
• Vomiting
• Constipation
• Having a dry mouth
• Gaining weight
• Increased appetite

Sadly, mirtazapine can result in some serious side effects. If you observe any of the following side effects whilst taking this antidepressant drug contact 111 for advice immediately. The side effects are as follows:

• Feeling constant confusion and constant headaches
• Experiencing frequent muscle cramps
• Severe pain in your back or stomach combined with nausea- this can be an indication of pancreatitis
• The whites of your eyes and/or skin turn yellow, indicating a problem with your liver
• Sore throat and mouth ulcers

Additionally, the atypical antidepressant agomelatine can also cause some side effects, with the common ones being:

• Dizziness
• Drowsiness
• Headache
• Abdominal pain
• Back pain
• Constipation
• Diarrhoea
• Vomiting
• Changes in weight

Uncommon and rare side effects can arise from taking agomelatine include the following:

• Aggression
• Mood changes
• Suicidal behaviors
• Tinnitus
• Blurred vision
• Hyperhidrosis (excessive sweating)
• Angioedema
• Hallucination
• Liver diseases

Efficacy of antidepressants in treating anxiety

Typically, SSRIs are given as the first line treatment for anxiety disorders , with escitalopram and sertraline being the first choice due to them having the highest efficacy (ability to produced the desired result of lessening anxiety symptoms).⁹ 

Other research, published in the British Medical Journal, supports this finding that SSRIs are the most effective drug in treating generalised anxiety disorder.¹⁰ However, how do SSRIs compare with other anxiety treatment options, such as cognitive behavioural therapy?

Cognitive behavioural therapy (CBT)

CBT is an alternative to taking antidepressants. SSRIs have been shown to be more effective in improving the psychological symptoms of anxiety. However, compared to CBT, SSRIs are less effective in improving the physical symptoms of anxiety,¹¹ such as:

• Upset stomach/stomach problems
• Headache
• Tension
• Fatigue

Lifestyle changes: exercise

Other anxiety treatment options include lifestyle changes, which begs the question: are lifestyle changes more effective than antidepressant drugs for treating anxiety?

Studies report that exercising, such as running therapy, is as effective as antidepressant therapy for anxiety.^12,13

Considerations for antidepressant treatment

Individual variability

Individual differences have to be taken into account when discussing your anxiety treatment options with your doctor, as you may not eligible for SSRIs, or you may have to seek advice from a doctor if you have one of the following:

• Diabetes
• Bipolar disorder
• A bleeding disorder
• Serious kidney, heart or liver problems
• If you are pregnant, as there are possible risks to the unborn baby
• If you are breastfeeding you may be prescribed paroxetine or sertraline as these are deemed as safe to use
• You are under the age of 18, as there is evidence of a higher risk of self-harm in under 18s who take SSRIs

Duration of treatment

When starting on an antidepressant drug to relieve the symptoms of anxiety, you should continue treatment for 4 weeks, 6 if you are elderly, before any change in antidepressant due to lack of efficacy.

Monitoring and adjustments

You should be monitored every 1-2 weeks when you first start taking antidepressant drugs. Typically, your doctor will prescribe you the lowest dose of the antidepressant drug that they believe will relieve your anxiety symptoms. However, this may need to be adjusted depending on how you respond to your treatment plan.

Summary

• Anxiety produces an excessive feeling of worry and fear
• As treatment for anxiety antidepressant medications can be taken
• Antidepressant medication classes include selective serotonin reuptake inhibitors (SSRIs), serotonin-noradrenaline reuptake inhibitors (SNRIs), and atypical antidepressants
• All antidepressants carry a risk of side effects
• The most effective class of antidepressant in reducing anxiety related symptoms are SSRIs
• Lifestyle changes, such as exercise and cognitive behavioural therapy have also been shown to reduce anxiety symptoms
• When prescribed an antidepressant your individuality will be considered to see which antidepressant is appropriate for you, and you will be prescribed the lowest dose to have the necessary effect in relieving your symptoms