Depression: An Overview
What it is, what causes it, prevention and treatment
Let’s start with the basics, what is depression and what are depressive disorders?
Life can sometimes give us challenges, hiccups, and disappointments. When this happens, it’s usual to feel a bit low or unhappy, but if you start to experience these feelings consistently over weeks or months, it becomes depression (also referred to as clinical depression or depressive disorder).
Depression is associated with many different symptoms including physical symptoms (including effects on weight, sleep, energy, etc.), psychological symptoms (including negative thoughts, difficulty concentrating, or making decisions), and emotional symptoms (including feeling angry or irritable, guilty, or loss of pleasure in hobbies and activities).
Statistics from the UK government show that 16% of adults suffered from depression. The rate is higher in people who have a chronic illness preventing them from working (59%), unpaid carers (37%), and people with disabilities (35%). Moreover, certain demographics experience depression more including, people living in low-income areas (25%), young people (28%) and women (19%) all experienced increased rates of depression.
As well as being a sizeable problem, depression seems to be a growing problem. According to the World Health Organisation (WHO), depression increased by 25% as a result of Covid. Even prior to the pandemic, depression was on the rise, particularly in young people, increasing from 10.1% in 2017 to 17.7% in 2020.
What causes depressive disorders?
Depression is caused by a huge range of factors. Genetics has been implicated as important both in studies across Europe and other global regions. While there is still a lack of consensus around the main genetic (and epigenetic) causes, it’s increasingly clear that genetics plays a role. If someone in your family has depression you are 2-3x more likely to have depression compared to the average (which is around 10% in the US). It’s also not clear yet how genes affect depression, but broadly speaking, it’s thought that genetics affect brain structures (e.g. the amygdala or HPA axis) and neurotransmitters (e.g. serotonin and dopamine) implicated in depression.
As with most mental health disorders, early childhood experiences have been implicated. One study found that over 75% of people struggling with depression had some form of childhood trauma (sexual abuse, significant loss, unsafe environment, etc.). This has been linked to things like negative thinking patterns, issues with self-esteem and agency, and attachment issues which may affect subsequent relationships.
Lifestyle has also been identified as important. One study found that those who tended to exercises less, were more likely to have depression. Sleep disturbances are also often found in people with depression. In one study, 83% of people with depression also had one symptom of a insomnia (compared to 36% of healthy controls). It’s difficult to untangle whether poor sleep causes depression or whether depression causes poor sleep, however it’s increasingly thought that both dynamics are at play, potentially causing negative downward spirals once you get stuck in this dynamic.
Diet has also been implicated. In one study, individuals with healthier diets (e.g. lots of fruits and vegetables, unprocessed food, low red meat consumption) were less likely to develop depression than those with unhealthy diets. Part of this effect is thought to manifest via the gut microbiome. Several bacteria in the gut microbiome have been linked to depression. Therefore, if your gut health deteriorates, this may make you more likely to experience depression and we now understand diet to be a significant factor in keeping a healthy gut microbiome.
Significant stressors in life also increase the likelihood of depression. The recent pandemic provided ample evidence for this on a global scale. Incidences of depression shot up in healthcare workers around the world as they were faced with increasingly dire working conditions and stressors. There is now research beginning to connect the dots between experiencing stress and the neurological and immune system effects which might lead to depression.
All in all, depression is understood to be a complex disorder. There are many factors that can lead to depression and its complexity may also explain why people experience depression differently. Some may suffer from greater emotional symptoms while others experience more physical symptoms.
How do we prevent and treat depressive disorders?
OK, time for some more positive news. What can we do about this growing challenge.
One of the most common forms of depression treatment are talking therapies, particularly cognitive behavioural therapy. This gets patients to challenge certain negative thoughts and behaviours through a range of techniques, giving patients a set of tools to help manage their symptoms. A review of over 400 studies with 50,000 patients found that CBT treatment greatly improves depression symptoms compared to control groups.
Given that lifestyle has been linked to depression causes, it’s no surprise that certain lifestyle changes have also been shown to have positive effects on depression. One review of over 200 high quality research studies found that exercise, from walking, to strength training, lead to a moderate improvement of depressive symptoms. A similar finding exists around diet whereby improving diet has been shown to reduce the symptoms of depression. In this review, dietary interventions for depression were shown to have significant (albeit small) effects on depression symptoms.
Part of the effect of diet on depression might be down to change in the gut microbiome. Supporting this idea is the discovery that probiotics and prebiotics have been shown across several studies to improve depression outcomes.
All in all, there are several ways that people suffering from depression can look to mitigate symptoms. It’s very much a case of trying what might work best for each individual. If you’re interested in microbiome-based solutions to depression, check out our website where we’re building new solutions to help people manage their mood.