What causes depression?

When does depression start to manifest itself? Gordon Harold is professor of the psychology of education and mental health at the University of Cambridge.

Gordon - Let me start by highlighting that depression is now recognized as the leading cause of disability globally. By 2030, it's expected that depression will be the leading cause of time lost illness, illness in the workplace, causing an estimated 16 trillion per year annually. And that estimate is pre pandemic. Interestingly, and following on from the discussion thus far, depression is often presented or understood as an adult specific disorder. And yet we know that 75% of serious psychiatric illness in adulthood, including depression, is in place before the age of 18 years. Therefore, understanding the early origins of depression is really, really important if we are going to more effectively support and treat this really debilitating condition across all ages.

Chris - So, if this is something which is manifest early, that would argue that the seeds are sown early. So is this a natural thing, something we are born with a tendency to develop? Is it a nurture thing, the environment we're growing up in, sows those seeds. Or is it both?

Gordon - It's a classic question Chris, and I think evidence is really quite clear in that there's no single cause of depression. Rather, there are multiple risk factors that if you like, converge or come together, that put an individual at significant risk for depression, onset and development. What we do know is that factors that put an individual at risk - family history, genetic factors, nature as you mentioned, stressful life events or experiences, environmental factors, personality factors, for example, low self-esteem or self-image can also be partly influenced by genetic factors. Severe or chronic physical illness, substance misuse, drugs, alcohol, different ages and stressful family, peer and other social relationship experiences, domestic neglect or adversity and peer based or social bullying, school or workplace for example.

Chris - That's an interesting one that you just brought up there in the sense that what we've seen in the modern era is the rise of the internet and in particular mobile devices, social media. And people are always there. There's no disconnect between that source of information and a person because they've always got a phone in their hand, especially younger people. Is that a catalyst for this happening more and more?

戈登——好吧,这当然是一个新的因素,一个新的dimension to the life that we now live from birth through to later stages in life. And we are only really beginning to examine and try to understand the role of the digital world as it's called, in relation to our day-to-day life and the impact that the digital world has on our mental ill health. We know for example, that adolescence is a really, really risky period for the onset of mental health problems, particularly depression. We know adolescents are in a period where there's stimulus seeking or risk taking behaviours. And increasingly the social media world is seen as an opportunity for the adolescent brain to pursue what it's designed to pursue from an evolutionary standpoint. The link between the digital world and social media is complex. Some evidence suggests that actual social media engagement and its impacts on mental ill health really varies by age and stage of life. And that actually where we see an increase in social media use or digital world engagement from an average, an average level of use, there does appear to be a link to poorer mental health related outcomes.

Chris - Do we need better regulation of it then, or do we need to know who the people are who are vulnerable to that so that we can put some safeguards in place so that those people don't fall into the trap of the social media negativity black hole that can happen? How do you advise we go forward then if we've identified this as a risk factor?

Gordon - I think it's really important to differentiate two elements of that question, Chris. One, differentiating mental health from mental ill health. They're not synonymous terms. Mental health is doing well, mental ill health is not doing well. And in terms of social media and digital world, it's separating out positives from negatives. So for example, social media allows much greater access to family and friends. That's potential positive as you mentioned in your previous question. A risk of course is that we can never switch off. We know from example, school-based engagement, bullying impacts outside of school context can continue through social media engagement and workplace engagement. At what point can you switch off from work? We really are only beginning to frame questions, but I think it's really important to differentiate both the positives and the negatives in trying to understand how social media, digital world can help versus hurt who's at risk, when and how and what we can do to improve outcomes for all ages and stages of life.

Chris - What should we, and that's the royal 'we', policymakers, be doing to put in place some kind of safeguard because one cannot ignore, as you started by saying extremely frankly and very poignantly, the enormous numbers of people now affected by depression across the world, not just in the UK. And there must be something that's driving that. What do we need to do to make sure that we turn the tide on this

Gordon - Improved understanding and education, Chris. I mean, to use a social media term, the key influencers in children's lives, parents, carers, teachers, social work, social care specialists, GPs and all those that work with young people who are at risk to understand what factors affect mental ill health and what can be done to improve outcomes. And also to recognize that depression specifically is a life course disorder. It starts early, can develop and progress to serious disorders, serious debilitating effects. Understanding what factors affect depression, being able to speak freely and openly and seek support and get the right type of support. Improving that interface will significantly impact the rising rate of depression in the UK and globally.