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✍🏻 Logan Wade | MBiol Pharmacology student & Undergraduate Regulatory Strategist at Pfizer
Be aware that this article contains mentions of self-harm and suicide. People who are sensitive to these topics should read with caution. If you're struggling with your mental health please click this link for resources.
What Is Depression? 🧠
Depression is a mood disorder characterised by low mood and loss of interest or pleasure (anhedonia).
This is sustained over a period of at least two weeks. Each experience with depression is different, but common symptoms include:
Feelings of guilt or worthlessness
Difficulty sleeping, or sleeping too much
Change in appetite
Decreased libido
Self-harm or suicidal thoughts
There are varying degrees of depression - milder forms, and major depressive disorder (MDD). Other distinct forms of depression include:
Seasonal affective disorder (SAD); which occurs at specific times of the year, often in the winter
Prenatal depression; which occurs in pregnant women
Postnatal depression; which occurs in women who have recently given birth
Persistent depressive disorder (PDD); which is classed as chronic as episodes last for a longer period of time
What Can Cause Depression? 🧬
Depression is not directly linked to any genetic or environmental factor. However, both can increase the risk of experiencing depression.
Heritability is how much a disorder can be attributed to genetic factors. Depression is somewhat heritable, meaning if someone has a parent or sibling with depression, they are at an increased risk of the condition.
Environmental factors include diet, physical activity and lifestyle changes (eg. moving to a new place). These stressors increase the risk of depression.
It is thought that depression is caused by a combination of many factors.
The biological basis of depression is still unknown, but there are some theories:
It is thought that decreased levels of serotonin, norepinephrine and dopamine is the basis of low mood. These neurotransmitters are responsible for feelings of pleasure. A deficit in these neurotransmitters could cause depression.
Excess cortisol has also been associated with depression. This is caused by an overactive stress response. This could explain the co-occurrence of depression and anxiety symptoms.
Decreased production of new nerve cells (neurogenesis) has been suggested to cause depression, as well as changes in brain circuitry.
What are the challenges with diagnosing depression? 🩺
There are several challenges associated with diagnosing depression.
Assessment of mental health relies on self-reporting and some patients lack insight into the severity of their illness.
Diagnosing depression often relies on checklists or questionnaires, and it could be argued that this oversimplifies the disorder.
For some people, there is also stigma or shame around self-reporting.
Currently, there are no biomarkers being used to diagnose depression.
What treatments are available for depression? 💊
There are non-pharmacological and pharmacological treatments for depression.
Non-pharmacological treatments
Talking therapies, for example, cognitive behavioural therapy (CBT). These therapies encourage the individual to become more able to manage their problems, and provide methods to dismiss or reframe harmful thoughts.
Lifestyle changes, eg. improving diet or becoming more active.
Pharmacological treatments
Selective serotonin re-uptake inhibitors (SSRIs). These antidepressant drugs increase the neurotransmitter serotonin in the body, which has antidepressant effects. SSRIs are the first line of treatment for depression, but they typically have a therapeutic lag (it takes 2-4 weeks for the drugs to work).
Monoamine oxidase inhibitors (MAOIs) increase the readily releasable pool of serotonin, as well as norepinephrine and dopamine. These were the first antidepressants to be used and were discovered accidentally when they were being used as anti-tuberculosis drugs.
Tricyclic antidepressants (TCAs) increase serotonin and norepinephrine in the synaptic cleft. They have off-target anti-cholinergic side effects, such as dry mouth.
It is important for a physician to consider other medications that the patient is taking, to avoid interactions between drugs. Sometimes, people have what is known as treatment-resistant depression (TRD), which is harder to treat.
One more extreme method is called electroconvulsive therapy, limited to a small number of patients. It involves electrical shocks to the brain while a patient is under anaesthesia, essentially inducing seizures. Though this has been misused in the past, it can now be a very effective treatment for severe cases.
What are the challenges with treating depression? 🏥
There are a number of challenges associated with treating depression.
Trial and error of which antidepressants are needed.
Some people, who suffer from TRD, may be searching a long time to find something that helps them.
A therapeutic lag on SSRIs, and sometimes an increased suicidality is seen in this time.
Drug adherence (taking the drug as required) could be an issue, especially in older patients
Some people will stop treatment due to side effects.
What does the future of antidepressants look like? 🔮
There are several drugs in the development pipeline.
Esketamine, a form of ketamine, has been used in some trials to alleviate depressive symptoms. However, this needs to be taken with caution as using esketamine can exacerbate existing psychosis.
Similarly, psychedelics such as psilocybin have been labelled a “breakthrough therapy” by the FDA.
Written by: Logan Wade (Content Writer)
Edited by: Grace Pountney (Founder and Director)
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