What Are Antidepressants?

  • Hima SaxenaMasters in Pharmacy - M.Pharm, Uttarakhand Technical University, India
  • Duyen NguyenMaster in Science - MSci Human Biology, University of Birmingham
  • Ellen Rogers MSc in Advanced Biological Sciences, University of Exeter

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Antidepressants are medications designed and used to alleviate the symptoms of depression, a mental health condition characterised by persistent sadness and loss of interest. Depression not only impacts your emotional well-being but can also hamper your daily functioning, significantly affecting your overall quality of life. With depression affecting millions globally, healthcare professionals are more and more frequently prescribing antidepressants to help these affected individuals.1 

Antidepressants function by regulating the activity of neurotransmitters, particularly serotonin and norepinephrine, within the brain.2 By understanding the mechanisms and various types of antidepressants available, you can gain valuable insights into how they are used effectively. In this article, we will delve into the different types of antidepressants and the criteria you must meet to be prescribed them, as well as their mechanisms of action, potential side effects, and possible withdrawal symptoms.

Conditions treated by antidepressants

Antidepressants can be used for these conditions:

Types of antidepressants

Antidepressants are medications used to treat depression and other depressive disorders.1 They are categorised into several classes based on their mechanism of action.

Selective serotonin reuptake inhibitors (SSRIs)

Serotonin is a chemical with a key role in regulating our moods. As such, low levels of serotonin have been linked to depression. SSRIs block the reuptake of serotonin by neurons, increasing the levels of serotonin and thereby enhancing neurotransmission. This leads to improved mood and reduced depressive symptoms. These are the most commonly prescribed antidepressants as they are associated with fewer side effects than other types of antidepressants. Examples of SSRIs include:3

Serotonin-norepinephrine reuptake inhibitors (SNRIs) 

Norepinephrine is another neurotransmitter involved in mood regulation and stress response. SNRIs block the reuptake of both serotonin and norepinephrine, increasing the levels of both - improving your mood and reducing depressive symptoms. Examples include venlafaxine and duloxetine.1

Tricyclic antidepressants (TCAs)

TCAs inhibit the reuptake of serotonin and norepinephrine and, whilst they are effective, they are rarely prescribed today due to their unpleasant side effects. They are mainly recommended for people with severe depression or other conditions such as obsessive-compulsive disorder (OCD) or bipolar disorder.

Examples of TCAs include:4

Monoamine oxidase inhibitors (MAOIs)

MAOIs increase levels of serotonin, norepinephrine, and dopamine in the brain by inhibiting the activity of an enzyme called monoamine oxidase which breaks down these neurotransmitters. They can cause severe side effects and are prescribed only by specialist doctors. Examples include:5

Atypical antidepressants

Atypical antidepressants have diverse mechanisms:

  • Bupropion acts on norepinephrine and dopamine
  • Mirtazapine affects serotonin and norepinephrine
  • Trazodone primarily works on serotonin receptors 

Side effects of antidepressants

The common side effects of antidepressants include:

Common side effects of SSRIs and SNRIs include:

Common side effects of TCAs can include:

  • Dry mouth
  • Blurred vision
  • Constipation
  • Problems passing urine (urinary retention)
  • Drowsiness
  • Dizziness
  • Weight gain
  • Excessive sweating (especially at night)
  • Fast heartbeat (tachycardia)

Potential complications of antidepressants

The potential complications associated with taking antidepressants include:

Serotonin syndrome

Serotonin syndrome is a life-threatening condition caused by abnormally high levels of serotonin in the body. It results from interactions between medications that affect serotonin levels, especially when taken together or at high dosages.6 

Symptoms of serotonin syndrome can include:

  • Confusion
  • Agitation
  • Muscle twitching
  • Sweating
  • Shivering
  • Diarrhoea

Symptoms of severe serotonin syndrome include:

Hyponatraemia

Hyponatremia is a medical condition characterised by an abnormally low concentration of sodium in the blood. When sodium levels become too low, fluid can accumulate within cells and cause various physiological problems. Elderly people are particularly vulnerable to this condition, as maintaining fluid levels can become challenging for the body as you age.7 

Mild hyponatraemia can cause symptoms such as:

  • Feeling sick
  • Headache
  • Muscle pain
  • Reduced appetite
  • Confusion

More severe hyponatraemia can cause:

  • Feeling listless and tired
  • Disorientation
  • Agitation
  • Psychosis
  • Seizures 

Severe instances of hyponatremia can lead to respiratory failure or induce a coma.

Diabetes

Taking SSRIs and/or TCAs for prolonged periods has been linked to a higher chance of getting type 2 diabetes. It's not clear if these antidepressants directly cause diabetes. Weight gain from using antidepressants may increase the risk of developing type 2 diabetes in some people.8

Symptoms of antidepressant withdrawal

Coming off of antidepressants may cause withdrawal symptoms, which are broadly referred to as antidepressant withdrawal syndrome. Not everyone will experience these symptoms, and their severity depends on factors like the type and dosage of the medication being stopped, and individual differences. Consult with a healthcare professional for guidance on tapering off antidepressants to minimise withdrawal risks.

The common withdrawal symptoms include:

  • Restlessness
  • Insomnia
  • Unsteadiness
  • Sweating
  • Stomach problems
  • Feeling irritable, anxious or confused

Cautions for antidepressants

While antidepressants can be effective in treating various mental health conditions, there are some cautions and considerations to keep in mind.

SSRIs

SSRIs may not be suitable for you if you have any of these conditions:

SNRIs

SNRIs may not be suitable for you if you have any of these conditions:

TCAs

TCAs may not be suitable for you if you have any of these conditions:

Who should not take antidepressants?

While antidepressants can be effective for many people, others are advised to take extra precautions when taking antidepressants - or to not take them at all. Here are some examples of the populations who may need to be cautious with, or completely avoid, antidepressant use:

Pregnant and breastfeeding women

The safety of antidepressants during pregnancy and breastfeeding is a complicated and evolving area of research. Some antidepressant medication may pose risks to the developing foetus or newborn. However, the decision to use or discontinue antidepressants during pregnancy should be carefully weighed against the potential risks of untreated depression.

Children and adolescents

The use of antidepressants in children and adolescents has been associated with an increased risk of suicidal thoughts and behaviours. The United States Food and Drug Administration (FDA) has issued warnings about the use of SSRIs and SNRIs in young people. However, in some cases, the benefits of antidepressant use may outweigh the risks, and antidepressants may be prescribed under close supervision.

Elderly individuals

Older adults may be more sensitive to the side effects of antidepressants, such as sedation and falls. Certain medications may also interact with other drugs commonly prescribed to the elderly. A healthcare professional will carefully assess the risks and benefits before prescribing antidepressants to older individuals.9

Individuals with bipolar disorder

Antidepressants may trigger manic or hypomanic episodes in individuals with bipolar disorder. Consequently, healthcare professionals may instead choose to prescribe mood stabilisers or other medications to bipolar patients in order to minimise their risk of cycling between depressive and manic states.10

Individuals with seizure disorders

Some antidepressants, such as bupropion, may increase the risk of seizures in individuals with seizure disorders. Individuals with a history of seizures or epilepsy may need to avoid certain antidepressants or be closely monitored.11

Always consult a qualified healthcare professional before starting or discontinuing any antidepressant medication, especially if you fall into any of the groups listed above. They can provide personalised advice based on an individual's health history and specific circumstances.

FAQ’s

What are the side effects of antidepressants?

Side effects of antidepressants may include:

  • Nausea
  • Insomnia
  • Weight changes
  • Sexual dysfunction
  • Drowsiness

Some individuals may also experience increased anxiety or suicidal thoughts. It's essential to consult a healthcare professional for personalised guidance and monitoring during antidepressant treatment to manage potential side effects effectively.

Can antidepressants affect your taste buds?

Antidepressants can potentially affect taste perception as a side effect, leading to changes in the way food tastes. However, individual responses vary, and not everyone experiences this. If taste alterations occur, they are usually temporary and may resolve once the body adjusts to the medication or if the medication is discontinued.

What do antidepressants do to the brain?

Antidepressants act on the brain by regulating chemicals called neurotransmitters, such as serotonin, norepinephrine, and dopamine. Antidepressants increase the availability of these chemicals. As these neurotransmitters are involved in mood regulation, this helps alleviate symptoms of depression and promotes a more balanced emotional state.

Summary

Antidepressants are a class of medications designed to alleviate symptoms of depression and related mood disorders. They work by modulating neurotransmitters, such as serotonin, norepinephrine, and dopamine, in the brain to restore balance. The common types of antidepressants include selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and tricyclic antidepressants (TCAs). These drugs aim to enhance your mood, reduce anxiety, and improve overall wellbeing. 

After being prescribed by healthcare professionals, antidepressants may take weeks to exert their full effect. The side effects of antidepressants and their impact on individuals vary, making it important that you are closely monitored during treatment. Despite their potential side effects, antidepressants are a vital component of mental health care and are often used very effectively alongside therapy and lifestyle interventions.

References

  1. Sheffler ZM, Patel P, Abdijadid S. Antidepressants. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Jan 26]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK538182/.
  2. Andrade C, Rao NSK. How antidepressant drugs act: A primer on neuroplasticity as the eventual mediator of antidepressant efficacy. Indian J. Psychiatry [Internet]. 2010 [cited 2024 Jan 26]; 52(4):378–86. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3025168/.
  3. Chu A, Wadhwa R. Selective Serotonin Reuptake Inhibitors. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Jan 26]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK554406/.
  4. Moraczewski J, Awosika AO, Aedma KK. Tricyclic Antidepressants. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Jan 26]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK557791/.
  5. Entzeroth M, Ratty AK. Monoamine Oxidase Inhibitors—Revisiting a Therapeutic Principle. OJD [Internet]. 2017 [cited 2024 Jan 26]; 06(02):31–68. Available from: http://www.scirp.org/journal/doi.aspx?DOI=10.4236/ojd.2017.62004.
  6. Volpi-Abadie J, Kaye AM, Kaye AD. Serotonin Syndrome. Ochsner Journal [Internet]. 2013 [cited 2024 Jan 26]; 13(4):533–40. Available from: https://www.ochsnerjournal.org/content/13/4/533.
  7. Adrogué HJ, Tucker BM, Madias NE. Diagnosis and Management of Hyponatremia: A Review. JAMA [Internet]. 2022 [cited 2024 Jan 26]; 328(3):280–91. Available from: https://emergencymed.org.il/wp-content/uploads/2022/08/jama_adrogu_2022_rv_220011_1657919726.49616.pdf.
  8. Alruwaili NS, Al-Kuraishy HM, Al-Gareeb AI, Albuhadily AK, Ragab AE, Alenazi AA, et al. Antidepressants and type 2 diabetes: highways to knowns and unknowns. Diabetol. Metab. Syndr. [Internet]. 2023 [cited 2024 Jan 26]; 15(1):179. Available from: https://doi.org/10.1186/s13098-023-01149-z.
  9. Poelgeest EP van, Pronk AC, Rhebergen D, Velde N van der. Depression, antidepressants and fall risk: therapeutic dilemmas—a clinical review. Eur. Geriatr. Med. [Internet]. 2021 [cited 2024 Jan 26]; 12(3):585–96. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8149338/.
  10. Shah N, Grover S, Rao GP. Clinical Practice Guidelines for Management of Bipolar Disorder. Indian J. Psychiatry [Internet]. 2017 [cited 2024 Jan 26]; 59(Suppl 1):S51–66. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5310104/.
  11. Hill T, Coupland C, Morriss R, Arthur A, Moore M, Hippisley-Cox J. Antidepressant use and risk of epilepsy and seizures in people aged 20 to 64 years: cohort study using a primary care database. BMC Psychiatry [Internet]. 2015 [cited 2024 Jan 26]; 15:315. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4683813/.

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Hima Saxena

Masters in Pharmacy - M.Pharm, Uttarakhand Technical University, India

Hima Saxena is a dedicated professional with a Master's degree in Pharmacy, who possesses a profound passion for medical science and its effective communication. Her articles adeptly blend pharmaceutical knowledge with writing skills, ensuring readers gain a comprehensive understanding of crucial medical topics. Her experience in writing and editing further strengthens her commitment to providing informative, precise, and easily accessible information. Hima is eager to leverage her knowledge and communication skills to enhance health awareness and knowledge through her writing.

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