13 / 11 / 2023
In 2017, the Global Burden of Health study calculated that 792 million people, or around one in ten, were living with a mental health condition. Depression and anxiety are by far the most common conditions, affecting approximately 264 million and 284 million people respectively. Given the global scale of these conditions and their impact on life, wellbeing, and the economy, depression and anxiety are major areas of focus for medical research.
Animals are used to study the neurological and psychological basis of depression and anxiety, as well as investigating the effect of genetic and environmental factors, and of the possible – usually pharmacological – treatment options. A quick search of “animal research depression” turns up 100s of recent studies outlining animal experiments and seeking to justify how they can benefit people who suffer from these conditions. For example, randomly picking from the first page of results reveals a paper from Diagnostics Journal in 2021 which states:
“In spite of the fact that none of the models completely resembles human depression, most animal models are relevant since they mimic many of the features observed in the human situation and may serve as a powerful tool for the study of the etiology, pathogenesis and treatment of depression, especially since only few patients respond to acute treatment. Relevance increases by the fact that human depression also has different facets and many possible etiologies and therapies.”
This type of research is based on the biomedical model which says that “mental disorders are brain diseases and emphasizes pharmacological treatment to target presumed biological abnormalities”. This biomedical perspective gained prominence in the 20th century over the previous view which looked primarily at the social determinants of mental health, in particular economic poverty. Over the last few decades, a rift has appeared between the medical psychiatric profession, which still adheres strongly to the biomedical model, and psychologists and other psychotherapists who think that the reductionist approach has gone too far. They, instead, argue patients’ experiences of depression and anxiety cannot be addressed without considering the whole person, including their relationships and social context, experiences (such as trauma or adverse childhood experiences), autonomy, opportunities, economic circumstances, and so on. This approach is called the biopsychosocial model and was originally put forward in the 1970s. It has been applied to many aspects of clinical care across different disease areas. However, primary research and, ironically, mental healthcare where it would seem most intuitive still appear to lag behind.
Humans are unusual in the animal kingdom as we not only have consciousness but can use language to convey our inner experiences. Attempts from people who suffer with depression and anxiety to articulate their reality provide us with a rich source of information about the conditions and, vitally, about what helps. To try to model this in mice, the most often used animal experiment is the ‘forced swim test‘ which has questionable validity, but has contributed to the development of antidepressant medications such as selective serotonin reuptake inhibitors, which, although controversial, do make a difference to many people’s lives. One of the many problems with using animals to solve the problem of depression in people is that we never actually know if the animals are ‘depressed’ as we understand it. We can look at behaviour like exhaustion, lethargy, lack of interest in food, but across humans behavioural responses to depression vary widely. Many aspects that we know exist, such as suicidal thoughts, are simply not possible to understand through animal research.
Only around 30% of patients diagnosed with depression who try medication find relief from their symptoms the first time around. A further 30% might find a medication that works after trial and error, which can take months. But there is an important proportion for whom medication never works, which is called treatment resistant depression, and the reductive biomedical model has failed to find answers.
Which raises the obvious question of are we looking in the right place?
If we listen to sufferers, they are clamouring for more, and more effective, in-person and talking therapies. Mental health research is already chronically underfunded relative to physical health research, and the same is true of funding for services. Medical treatment approaches (the ‘magic pill’) might continue to be an attractive goal for both researchers and clinicians, but in an age of dwindling resources where our need to prioritise is all the more pressing… Is it the right one? It seems a little like looking for the most effective crash diet to tackle obesity when what’s needed for most people is support to make sustainable long-term healthy changes.
We need to invest more in researching and funding person-centred support for depression and anxiety, and tackling the social contributors to mental ill health. The most depressing thing (pun intended) is that those with the money for research and development (pharmaceutical companies) have to develop a marketable product at the end of the day. That is their business model, and it will continue to prioritise work into medications (something for which in other areas we should be grateful). Talking therapies are not a marketable product which can produce a return on investment in the same way, and consequently will never be a viable subject for commercial R&D expenditure. Why can’t we at least attempt to redress the balance by focusing all public research funding into how to build and sustain effective human-relevant psychotherapeutic services? When there is so much we don’t yet understand, and so many people suffering, it’s hard to justify that public funding should be spent on further animal tests to understand the workings of depressive disorders.
We’ve done 50 years of that now; it’s helped some people and made an awful lot of money for others. This Mental Health Awareness Week, let’s move forward by listening to sufferers and properly funding support services and a society that aims to reduce or eliminate the contributors to depression. Is that too much to ask? Sadly, it probably is.
Thank you to Mental Health Foundation for organising this important week and giving us the opportunity to discuss these difficult, important topics. Find out more about Mental Health Awareness week.