- Human and animal studies have revealed CBD’s antidepressant and anxiolytic (anxiety-reducing) properties that may help improve various conditions related to mental health, including major depressive disorder(1).
- The 2018 study published in the journal Frontiers in Immunology concluded that CBD may also treat other psychiatric conditions. These conditions include anxiety disorders, epilepsy, schizophrenia, Parkinson’s disease, and sleep disorders(2).
- Studies have shown that CBD may help manage depression as the compound activates 5-HT1A receptor(3) and facilitates the formation of new neurons in the hippocampus(4).
- Still, further study is needed to conclude that CBD alone can help treat psychiatric disorders like depression.
Can CBD Help with Depression?
CBD is known to help treat various ailments, including psychiatric conditions.
Several studies have shown that CBD may help relieve the clinical signs of depression. Researchers have noted that CBD may also help alleviate anxiety, a depression symptom.
In a 2011 study, patients with a social anxiety disorder (SAD) were subjected to a simulation public speaking test and given 600 milligrams (mg) of CBD.
Results showed that patients who were pretreated with CBD experienced significant improvement in their symptoms than those who took a placebo(5).
Additionally, patients who took CBD reported reduced anxiety, cognitive impairment, and discomfort when giving their speech.
Another study has noted that CBD may help alleviate the symptoms of neuropsychiatric disorders, like epilepsy and schizophrenia.
According to the researchers, CBD has the potential to calm the central nervous system(6). The same findings were reported by a 2015 study(7).
The 2015 study observed CBD’s therapeutic effects on generalized anxiety disorder (GAD), social anxiety disorder (SAD), panic disorder (PD), obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD).
A study published in the journal CNS & Neurological Disorders Drug Targets outlined the benefits of CBD(8). The research highlighted CBD not only as an anxiolytic treatment but also as an antidepressant that treats the symptoms of depression.
Moreover, CBD’s stress- and anxiety-reducing properties may be responsible for its potential to help with high blood pressure.
The study suggested that CBD may alleviate depression, epilepsy, schizophrenia, substance abuse and dependence, social phobia, bipolar disorder, PTSD, Parkinson’s disease, and sleep disorders(9).
A journal outlined the case of a 16-year old male with multiple substance use disorders. He also had severe depression, social phobia, and narcissistic personality disorder(10).
The adolescent’s treatment with antidepressants has proven unsuccessful, so he sought help from a public clinic in 2018.
In the study, the researchers administered CBD capsules in various dosages for eight weeks. The patient’s simple phobias and symptoms of depression, anxiety, paranoia, and dissociation improved.
Without withdrawal symptoms, the patient also quit taking illegal drugs like cannabis, cocaine, and ecstasy.
It is the first report on CBD’s positive results on patients with multiple substance use disorders.
A study published in the Journal of Cannabis Research was conducted to review the therapeutic benefits of CBD and CBD-containing compounds, like nabiximols, in treating various psychiatric disorders and cannabis dependence(11).
Nabiximols is an extract from Cannabis sativa that has been purified into a 1:1 ratio of CBD and tetrahydrocannabinol (THC). Sativex is a brand of nabiximols.
In the research, CBD was given to the test subjects in various ways, including oral ingestion, inhalation spray, and sublingual administration (under the tongue).
The study revealed that compared to oral administration, inhaling CBD had higher bioavailability (11% to 43%). Bioavailability is the fraction of the drug that reaches the blood.
CBD and nabiximols were most effective in treating cannabis use-related disorders. The two compounds also proved promising in treating other psychiatric disorders because of their antipsychotic properties.
Results suggest that the anxiolytic and neuroprotective effects of cannabidiol and nabiximols contributed to the treatment.
In schizophrenia and psychosis cases, higher doses of CBD (above 1200 mg daily) showed potential therapeutic benefits, especially in patients with Parkinson’s disease.
The study also supported the use of CBD in treating anxiety disorders, like post-traumatic stress disorders and social performance-related anxiety.
Patients with autism spectrum disorder who received CBD also exhibited reduced hyperactivity, self-injurious behaviors, insomnia, and anxiety.
In the study, however, CBD was ineffective in treating bipolar disorder.
The authors emphasized the need for further research to determine whether CBD alone can alleviate the disorders mentioned above. Dosing may be the reason that it did not show efficacy in bipolar patients.
Still, the researchers recognize CBD and CBD compounds’ therapeutic potential in relieving symptoms of psychosis and improving cognitive impairment due to various conditions.
Another study, published in the journal Molecular Neurobiology, compared CBD to antidepressants and noted CBD’s fast-acting effects(12). Unlike CBD, depression medications have a “substantial time lag” before taking effect in the body.
How CBD Works to Alleviate Symptoms of Depression
Researchers have found that CBD interacts with 5-HT1A receptors(13). This interaction produces anxiolytic and antidepressant effects in the dorsolateral periaqueductal gray (dlPAG) of the brain.
The dlPAG is the region of the brain that mediates aversive emotional experiences.
A 5-HT1A receptor is a serotonin receptor subtype that can be found in the brain. When this receptor is activated, it helps in the mechanism of action of antidepressant, anxiolytic, and antipsychotic drugs(14).
Postsynaptic 5-HT1A receptors are located in the brain’s areas responsible for controlling mood, cognition, and memory. Therefore, these serotonin receptors can help in the treatment of neuropsychiatric disorders(15).
5-HT1A receptors are essential in curbing depression. For instance, antidepressants increase postsynaptic 5-HT1A signaling(16).
Patients exhibiting suicidal behaviors were also observed to have reduced numbers of the receptor. Researchers have also concluded that the dysfunction of 5-HT1A receptors could result in depressive disorders(17).
A 2010 study conducted in rodents has proven that CBD activates 5-HT1A receptors, producing anxiolytic effects in the test subjects(18).
As a substance with antidepressant-like effects, CBD also aids in increasing the expression of the brain-derived neurotrophic factor (BDNF).
Depressed animals and humans exhibit decreased levels of BDNF(19). BDNF is a protein that is essential in the growth and survival of neurons(20).
A 2018 study outlined how CBD may increase the release of BDNF, which helps in brain neuroplasticity, particularly new synaptic formation and cell proliferation(21). Neuroplasticity is required to achieve antidepressant effects.
As an antidepressant, CBD may also contribute to hippocampal neurogenesis, the production of new neurons in the hippocampus.
Neurogenesis is known to aid in neural regeneration(22). The regeneration process involves forming new neurons to regrow and repair the nervous tissues.
A study conducted in mice has shown that the hippocampus‘ neuron production attenuates depression-related behaviors(23).
Research published in the journal Current Neuropharmacology investigated the link between the endocannabinoid system (ECS), the formation of neurons, and antidepressants(24).
The ECS regulates several functions, like mood, appetite, sleep, memory, fertility, and reproduction. CB1 and CB2 are the two central cannabinoid receptors of ECS.
The researchers observed that when CB1 and CB2 are manipulated, they can contribute to the formation of neurons in the hippocampus.
Three types of cannabinoids interact with the ECS, namely endocannabinoids, phytocannabinoids, and lab-derived cannabinoids.
The body produces endocannabinoids. Meanwhile, phytocannabinoids (CBD and THC) are derived from the cannabis or marijuana plant.
A study in 2018 was conducted on cannabis users. According to the research, prolonged use of cannabis can have detrimental effects on the hippocampus, primarily due to the THC component(25).
The study revealed that CBD has neuroprotective properties that may reverse these effects. It also suggested that CBD may help in hippocampal neurogenesis. Researchers noted that CBD’s pro neurogenic action may have anxiolytic effects.
The 2018 study recommended that CBD may be used in alleviating cannabis dependence and several psychiatric disorders involving hippocampal pathologies. These disorders include schizophrenia, Alzheimer’s, and major depressive disorder.
CBD vs. Antidepressant Medications
Psychiatric disorders, like depression, should not be left untreated as they can worsen. Depression is usually treated by selective serotonin reuptake inhibitors (SSRIs) or antidepressants.
SSRIs are prescription drugs and cannot be bought over the counter. These drugs are also used as anxiety medications.
Examples of these antidepressant medications include citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac), paroxetine (Paxil, Pexeva), and sertraline (Zoloft).
While these medications treat depression, it takes a significant amount of time before the drugs take effect. These antidepressant medications also have adverse side effects.
People with depression often go to psychotherapy (talk therapy) and support groups. They employ self-help and self-management approaches to treat their major depressive disorder.
Meanwhile, some people take natural supplements, like St. John’s wort. This herb reduces levels of cortisol, a stress-related hormone. St. John’s wort also increases neurotransmitters’ norepinephrine, dopamine, and serotonin levels(26).
According to Harvard Medical School, however, using St. John’s wort is not as effective as prescription medications like antidepressants. The herb also causes similar side effects(27).
When taken alongside antidepressants, St. John’s wort may cause serotonin syndrome. This potentially fatal disorder happens when excess serotonin builds up in the body.
Exercise is useful in alleviating several medical conditions, including depression. This activity gives the body feel-good chemicals called endorphins and aids in nerve cell growth in the hippocampus(28).
According to a study, exercise increases BDNF levels in the brain, thereby contributing to the improvement of depression(29).
CBD may also be used in wellness practices, such as aromatherapy and massage. The infusion of CBD hemp extract and essential oils is found to have therapeutic benefits.
According to a study, using essential oils in massages helps reduce anxiety and depression symptoms, relieve pain and stress, and improve sleep(30).
How to Use CBD Oil for Depression
One may take CBD oil using various methods, depending on which form would best suit the patient’s lifestyle.
CBD comes in different formulations, such as oils, tinctures (drops), gummies, capsules sprays, soft gels, or capsules.
These products can be taken sublingually (under the tongue), swallowed, added to food or beverages, vaped, or applied to the skin.
Tinctures may be taken sublingually using the dropper. Let the oil sit for 60 seconds to a minute and a half before swallowing.
CBD tinctures allow patients to adjust the dosage of the product quickly.
Meanwhile, CBD gummies and capsules provide a fixed dose of CBD. One can quickly ingest these CBD products and conveniently bring them anywhere.
With the ingestion method, CBD passes through the digestive tract, and the liver metabolizes its compounds before it reaches the bloodstream.
CBD oils can also be used during massages. Some CBD products are infused with essential oils that could be therapeutic, especially to patients who need to be relieved of stress.
CBD is also available in topical forms like creams and lotions. Topical CBD products are usually used for pain and inflammation management but seldom for treating depression.
Topical CBD has limited absorption. It is best to purchase products that indicate the use of nanotechnology, encapsulation, or CBD micellization because the CBD can be transmitted through dermal layers instead of only staying on the skin.
Some people also prefer taking their CBD in vape form. It is a popular method because users ingest the substance instantly, thereby giving the quickest results.
A 2020 study noted that the bioavailability of CBD is higher when it is inhaled (11% to 43%) than when it is orally ingested (11% to 13%)(31).
Though the effects are instantaneous because CBD enters the bloodstream via the lungs and not the digestive system, vaping can lead to throat irritation or coughing(32).
Before deciding to inhale CBD via vape pens, it is recommended to proceed with caution. Studies have shown that lung injuries and diseases are associated with vaping(33).
There are three types of CBD oils patients with depression can choose from, full-spectrum CBD oil, broad-spectrum, and isolates.
Full-spectrum CBD oil utilizes all the components of a cannabis plant, including trace amounts of THC, terpenes, flavonoids, fatty acids, and essential oils.
However, THC may cause psychoactive effects in people and can be detected via drug tests.
For those who want to avoid these risks, using broad-spectrum CBD may prove useful. Broad-spectrum CBD oils contain all the components of full-spectrum oils without the THC.
Those who want to use CBD in its purest form or are allergic to other hemp plant components may purchase CBD isolates. They are pure CBD, as they only have isolated cannabidiol.
Buying CBD Legally
Although CBD is readily accessible in most parts of the United States, state laws may vary. Under the Farm Bill of 2018, hemp-derived CBD products with less than 0.3% THC are federally legal(34).
CBD products are available at local dispensaries and health shops. Some states may require citizens to present a prescription or medical marijuana card before buying CBD-rich oils with more than 0.3% THC(35).
According to the Anxiety and Depression Association of America (ADAA), CBD’s pricing regulations only apply to products approved by the Food and Drug Administration (FDA)(36).
The vast majority of CBD products can also be purchased online. It is recommended to buy directly from the CBD brand’s official website.
Consumers should choose CBD products that have undergone lab testing. Third-party lab reports indicate the total amount of cannabinoids and absence of contaminants, including pesticides, bacteria, and heavy metals.
CBD Risks and Safety Considerations
According to the World Health Organization (WHO), CBD “is generally well-tolerated with a good safety profile(37).”
However, the side effects of CBD may include dry mouth, nausea, fatigue, drowsiness, loss of appetite and gastrointestinal problems, diarrhea, changes in alertness and mood, and liver damage(38).
The CYP450 liver enzymes are responsible for breaking down several phytocannabinoids, including CBD(39). Thus, it is not recommended to take CBD alongside medications with a “grapefruit warning(40).”
CBD in high doses may also interact with other medications, such as antidepressants, immune suppressors, and blood thinners, and raise their levels in one’s system(41).
Another significant safety concern is CBD being primarily marketed and sold as a supplement and not a medication. The US FDA currently does not regulate the purity and safety of dietary supplements(42).
The FDA has approved only one CBD product for the treatment of epilepsy, Epidiolex(43). Further investigation and clinical trials are still needed to prove that CBD is a safe and effective treatment for various conditions.
For now, the FDA advises people not to depend solely on CBD as an alternative to conventional healthcare(44).
Understanding Anxiety & Depression
Anxiety and depression are detrimental to those who have them. These disorders significantly affect not only their health and well-being but also their social life and productivity.
These disorders are closely linked, although they are still different from each other. Depression is a more severe condition, while anxiety disorders could also trigger depression.
The US Department of Health & Human Services lists different types of anxiety disorders(45):
- Generalized anxiety disorder (GAD) – GAD is characterized by exaggerated worry, chronic anxiety, and tension.
- Panic disorder (PD) – PD is described by unexpected and repeated episodes of intense fear and panic attacks.
- Post-traumatic stress disorder (PTSD) – PTSD may develop after exposure to a terrifying ordeal or traumatic events.
- Social anxiety disorder (SAD) – SAD is characterized by excessive self-consciousness and overwhelming anxiety in everyday social situations.
- Obsessive-compulsive disorder (OCD) – OCD is characterized by repetitive behaviors or compulsion and recurrent, unwanted thoughts or obsessions.
These anxiety disorders may have different treatments. However, these disorders generally share the same symptoms, like restlessness, a feeling of dread or being “on-edge,” irritability, and difficulty concentrating and sleeping(46).
Although the causes of anxiety vary, it is usually caused by biological factors, like genetics or chronic physical ailments and injuries.
Psychological or social factors may also contribute to anxiety. Some factors include experiences of poverty, childhood trauma, employment status, living or work environments, and family and personal relationships.
Meanwhile, depression could vary in people, from mild to severe. The symptoms are also different, but depressed people generally feel an encompassing sadness or hopelessness(47).
Although depression and anxiety share similar causes, depression is a more complicated condition. Sudden life-changing events can also cause it.
These events may include pregnancies, life-threatening diseases like cancer, heart disease, chronic pain, and diabetes.
Conclusion
In recent years, several studies showed the health benefits of CBD in managing the symptoms of anxiety and depression. However, research on whether CBD alone can suffice in treating the said psychiatric disorders is still lacking.
CBD has anxiolytic, antipsychotic, and antidepressant properties. It activates 5-HT1A receptors, resulting in the reduction of depression.
CBD may increase brain-derived neurotrophic factor, which is low in depressed animals and humans.
Part of CBD’s antidepressant properties is its ability to facilitate the formation of neurons in the hippocampus. These properties of CBD may explain its positive effects on attenuating anxiety, psychotic, and depressive behaviors.
CBD may help improve sleep, reduce stress, enhance cognitive function, and stabilize mood, thereby making it useful in managing symptoms of depression.
Despite these developments, more research still needs to be done. However, it should be recognized that CBD has much potential in treating depression, especially since it has minimal side effects compared to SSRIs.
Before using CBD oil for anxiety and depression, it is best to consult with a medical professional.
- Crippa, José A et al. “Translational Investigation of the Therapeutic Potential of Cannabidiol (CBD): Toward a New Age.” Frontiers in immunology vol. 9 2009. 21 Sep. 2018, doi:10.3389/fimmu.2018.02009
- Ibid.
- de Mello Schier, Alexandre R et al. “Antidepressant-like and anxiolytic-like effects of cannabidiol: a chemical compound of Cannabis sativa.” CNS & neurological disorders drug targets vol. 13,6 (2014): 953-60. doi:10.2174/1871527313666140612114838
- Beale, Camilla et al. “Prolonged Cannabidiol Treatment Effects on Hippocampal Subfield Volumes in Current Cannabis Users.” Cannabis and cannabinoid research vol. 3,1 94-107. 1 Apr. 2018, doi:10.1089/can.2017.0047
- Bergamaschi, Mateus M et al. “Cannabidiol reduces the anxiety induced by simulated public speaking in treatment-naïve social phobia patients.” Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology vol. 36,6 (2011): 1219-26. doi:10.1038/npp.2011.6
- Shannon, Scott et al. “Cannabidiol in Anxiety and Sleep: A Large Case Series.” The Permanente journal vol. 23 (2019): 18-041. doi:10.7812/TPP/18-041
- Blessing, Esther M et al. “Cannabidiol as a Potential Treatment for Anxiety Disorders.” Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics vol. 12,4 (2015): 825-36. doi:10.1007/s13311-015-0387-1
- de Mello Schier, A. 2014. op. cit.
- Crippa, J. 2018 Sep. 21. op. cit.
- Laczkovics, C., Kothgassner, O.D., Felnhofer, A. et al. Cannabidiol treatment in an adolescent with multiple substance abuse, social anxiety and depression. Neuropsychiatr (2020). https://doi.org/10.1007/s40211-020-00334-0
- Khan, R., Naveed, S., Mian, N. et al. The therapeutic role of Cannabidiol in mental health: a systematic review. J Cannabis Res 2, 2 (2020). https://doi.org/10.1186/s42238-019-0012-y
- Sales, Amanda J et al. “Cannabidiol Induces Rapid and Sustained Antidepressant-Like Effects Through Increased BDNF Signaling and Synaptogenesis in the Prefrontal Cortex.” Molecular neurobiology vol. 56,2 (2019): 1070-1081. doi:10.1007/s12035-018-1143-4
- de Mello Schier, A. 2014. op. cit.
- “5-HT1A Receptors in Psychopharmacology.” Edited by Flavio Guzman, Psychopharmacology Institute, psychopharmacologyinstitute.com/publication/5-ht1a-receptors-in-psychopharmacology-2123.
- Guzman, F. op. cit.
- Ibid.
- Ibid.
- Zanelati, T V et al. “Antidepressant-like effects of cannabidiol in mice: possible involvement of 5-HT1A receptors.” British journal of pharmacology vol. 159,1 (2010): 122-8. doi:10.1111/j.1476-5381.2009.00521.x
- de Mello Schier, A. 2014. op. cit.
- Bathina, Siresha, and Undurti N Das. “Brain-derived neurotrophic factor and its clinical implications.” Archives of medical science : AMS vol. 11,6 (2015): 1164-78. doi:10.5114/aoms.2015.56342
- Sartim, Ariandra G., et al. “Hippocampal Mammalian Target of Rapamycin Is Implicated in Stress-Coping Behavior Induced by Cannabidiol in the Forced Swim Test.” Journal of Psychopharmacology, vol. 32, no. 8, Aug. 2018, pp. 922–931, doi:10.1177/0269881118784877.
- Enciu, A. M., Nicolescu, M. I., Manole, C. G., Mureşanu, D. F., Popescu, L. M., & Popescu, B. O. (2011). Neuroregeneration in neurodegenerative disorders. BMC neurology, 11(1), 75.
- Hill, Alexis S et al. “Increasing Adult Hippocampal Neurogenesis is Sufficient to Reduce Anxiety and Depression-Like Behaviors.” Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology vol. 40,10 (2015): 2368-78. doi:10.1038/npp.2015.85
- Fogaça, Manoela Viar et al. “Cannabinoids, Neurogenesis and Antidepressant Drugs: Is there a Link?.” Current neuropharmacology vol. 11,3 (2013): 263-75. doi:10.2174/1570159X11311030003
- Beale, C. 2018 Apr. 1. op. cit.
- Health Publishing. “What Are the Real Risks of Antidepressants?” Harvard Health, Mar. 2014, www.health.harvard.edu/mind-and-mood/what-are-the-real-risks-of-antidepressants.
- Harvard Health Publishing. “Herbal and Dietary Supplements for Depression.” Harvard Health, Oct. 2008, www.health.harvard.edu/newsletter_article/Herbal_and_dietary_supplements_for_depression.
- Ibid.
- Harvard Health Publishing. “Exercise Is an All-Natural Treatment to Fight Depression.” Harvard Health, July 2013, www.health.harvard.edu/mind-and-mood/exercise-is-an-all-natural-treatment-to-fight-depression.
- Louis, M., & Kowalski, S. D. (2002). Use of aromatherapy with hospice patients to decrease pain, anxiety, and depression and to promote an increased sense of well-being. American Journal of Hospice and Palliative Medicine®, 19(6), 381-386.
- Khan, R. 2020 Jan. 2. op. cit.
- Farsalinos, K. E., Romagna, G., Tsiapras, D., Kyrzopoulos, S., & Voudris, V. (2014). Characteristics, perceived side effects and benefits of electronic cigarette use: a worldwide survey of more than 19,000 consumers. International journal of environmental research and public health, 11(4), 4356-4373.
- Broderick, S. (2020). What Does Vaping Do to Your Lungs? Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/wellness-and-prevention/what-does-vaping-do-to-your-lungs
- Corroon, J., & Kight, R. (2018). Regulatory status of cannabidiol in the United States: a perspective. Cannabis and cannabinoid research, 3(1), 190-194.
- ProCon.org. States with Legal Cannabidiol (CBD). Retrieved from: https://medicalmarijuana.procon.org/states-with-legal-cannabidiol-cbd/
- ADAA.org. (June 2019). Can CBD Help with My Anxiety and Depression?. Retrieved from: https://adaa.org/understanding-anxiety/cbd
- World Health Organization (WHO). (2018). Cannabidiol (CBD) Critical Review Report. https://www.who.int/medicines/access/controlled-substances/CannabidiolCriticalReview.pdf
- Alsherbiny MA, Li CG. Medicinal Cannabis-Potential Drug Interactions. Medicines (Basel). 2018;6(1):3. Published 2018 Dec 23. DOI:10.3390/medicines6010003.
- U.S. Food and Drug Administration. (2017, July 18). Grapefruit Juice and Some Drugs Don’t Mix. Retrieved from https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix.
- Harvard Health Publishing. (2019, Oct). Know the facts about CBD products. Retrieved from https://www.health.harvard.edu/staying-healthy/know-the-facts-about-cbd-products.
- US Drug Enforcement Administration. (December 2015). DEA Eases Requirements For FDA-Approved Clinical Trials On Cannabidiol. Retrieved from: https://www.dea.gov/press-releases/2015/12/23/dea-eases-requirements-fda-approved-clinical-trials-cannabidiol
- FDA.gov. (October 2020). FDA Regulation of Cannabis and Cannabis-Derived Products, Including Cannabidiol (CBD). Retrieved from: https://www.fda.gov/news-events/public-health-focus/fda-regulation-cannabis-and-cannabis-derived-products-including-cannabidiol-cbd
- FDA.gov. (2018, June 25). FDA approves first drug comprised of an active ingredient derived from marijuana to treat rare, severe forms of epilepsy. Retrieved from https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-comprised-active-ingredient-derived-marijuana-treat-rare-severe-forms.
- Regulation of Cannabis and Cannabis-Derived Products, Including Cannabidiol (CBD). op. cit.
- HHS. (2014, Feb 12). What are the five major types of anxiety disorders? Retrieved from: https://www.hhs.gov/answers/mental-health-and-substance-abuse/what-are-the-five-major-types-of-anxiety-disorders/index.html.
- Mental Health Foundation. (12 Jan. 2018). “Anxiety.” Retrieved from: www.mentalhealth.org.uk/a-to-z/a/anxiety.
- Mental Health Foundation. (15 Jan. 2018). “Depression.” Retrieved from: www.mentalhealth.org.uk/a-to-z/d/depression.