There are many routes to mental well-being. In The Balanced Brain, neuroscientist Camilla Nord offers a fascinating tour of the scientific developments that are revolutionising the way we think about mental health, showing why and how events—and treatments—can affect people in such different ways.
What motivated you to write a book about mental health?
CN: I wrote The Balanced Brain because my research as a neuroscientist over the past decade has radically changed my perspective of what mental health is. ‘Mental health’ as a concept is practically ubiquitous today—something we hear and talk about in our lives almost every day. It’s of vital importance medically, of course, but it also represents a societal shift: a renewed focus on wellbeing, thriving, ‘feeling well’. I’m glad it’s being discussed—but there are some crucial things I think everyone gets wrong about mental health. Mental health feels subjectively abstract, ephemeral. But it is not: it comes from concrete, measurable phenomena generated by our brains and wider nervous systems. For example, our mood is strongly influenced by our brain’s expectations: what our brain predicts about the environment based on what it has experienced before. These expectations are physically instantiated, and have physical effects on regions of the brain involved in processing the world around you. So mental health might seem abstract, but it is tangible—and because it is tangible, scientists now have a better understanding of what it is and how to treat it.
What does that mean for the causes of mental health—is it essentially all your biology?
CN: In a sense yes, but only because social phenomena affect your mental health via your biology. I sometimes use the example of lung cancer: your environment, such as smoking and pollution, clearly plays an important role in lung cancer. But these risks only cause disease via local biological changes- in your lungs, circulatory system, and so on. Similarly, the various life factors that can increase your risk of mental health problems also change your biology: your brain, and your body. Their effect on mental health is entirely mediated through biological processes, and their effect on cognition—perception, emotion, memory, and so on. That means that our concept of mental health needs to include the brain—and, I would argue, the wider body.
The body is something that is rarely discussed in the context of mental health. In what way can the body impact mental health?
CN: In the 21st century science, there has been a resurgence of interest in the relationship between the body and mental health. This comes out of a wider movement examining the influence of internal states in the body on emotion and cognition more generally. For example, some of my lab’s work has shown that the state of the stomach influences the emotion disgust—and other labs’ work has shown that signals from the heart are involved in fear processing, which may play an important role in anxiety and other related disorders.
Does this mean we could be managing or treating our own mental health via the body?
CN: We already are, in many cases. Exercise has a large, consistent effect on mental health—epidemiologically, exercise improves mental health even more than a big economic change, like moving from low- to medium-income. But there is also a suggestion that new treatments could focus on the body, such as anti-inflammatory drugs for some mental health problems, or even the connection between the body and the brain, which is targeted by treatments like electrical stimulation of the vagus nerve. The body-brain connection actually means many things—comes from many sources, including internal organs like the gut but also widespread systems like the immune system—and disruptions can occur at different levels, both at the level of the body itself, or in the brain’s perception of the body, or in the pathways of communication between the two.
Does this mean some aspects of physical and mental health overlap?
CN: One of the best examples of this overlap is pain. Pain feels like it comes from the body—and some of it does, from pain receptors called ‘nociceptors’ that send signals to our brain. But our experience of pain is created by the brain. The brain has the ability to dampen down pain signals—help you ignore painful input, escape a predator even when you’ve been injured. The brain also has the ability to enhance pain signals, and even create them in the absence of nociception entirely. I write in The Balanced Brain about functional neurological symptoms where symptoms like weakness, paralysis, or even blindness, are generated by the brain, but experienced in exactly the same way as physical disabilities. The way we talk about this can be pejorative—‘psychogenic’ symptoms is a more old-fashioned term, and not very helpful scientifically. Really, functional symptoms arise via brain mechanisms, outside of someone’s conscious awareness, and are a relatively common cause of hugely disabling symptoms, that can occur with or without poor mental health. They are what some call ‘the most common disorder people haven’t heard of’.
What do you see as the role of placebo effects in mental health—it seems like an unusual topic for a mental health book?
CN: I write about the placebo effect in such detail in The Balanced Brain because it’s such a clear way that expectations can change your biology. Placebos are not biologically inert at the level of your brain. If you take a medication expecting changes to pain, depression, or any other symptom, a wide network of changes in the brain occur, amazingly similar to the very changes caused by real pain medications (or depression medications, if that is your expectation). And the opposite occurs too—the nocebo effect, where you might experience side effects from a treatment wholly from your expectations.
Some mental health treatments, like antidepressants, have been accused of largely being placebos. Are they?
CN: Sadly there has been a plethora of disinformation about antidepressants recently. In part it comes from the reality that antidepressants do not work for everyone, and have genuine adverse effects for some people. Mixed with this is the fact that antidepressants do not necessarily correct an underlying serotonin deficit—a public misunderstanding I explain in The Balanced Brain, when I talk about how antidepressants really work on the brain. Nevertheless—yes, the placebo effect influences every effective medical treatment, including antidepressants. But antidepressants also work above and beyond comparable placebos, in many very large, robust trials. Maybe more difficult is the role of placebo effects in treatments like psychological therapy and psychedelics. For these treatments, it is essentially impossible to run the sort of experiment you need to disentangle placebo and ‘real’ treatment effects—a double-blind randomised controlled trial—because in psychological therapy, the therapist always knows what therapy they are delivering, and in psychedelics, patients are almost always able to tell when they are in an ‘active’ condition. In both, the placebo effect may partly contribute to how effective a treatment seems. I even wonder if cognitive therapies themselves work a bit like the placebo effect: directly targeting beliefs and expectations about the world.
Is there a role for treatments that now seem quite outdated like ECT—electroconvulsive therapy—in mental health?
CN: ECT is a type of brain stimulation which can effectively treat patients with very severe depression who do not respond to typical treatments. But today it is by no means the only brain stimulation used for mental health problems. In North America, transcranial magnetic stimulation therapy for depression, a mild, noninvasive way to change brain activity in the prefrontal cortex, is becoming more and more common, and is at least as effective as antidepressants—maybe even more so. In more severe cases, there may also be a role for surgical deep brain stimulation, or DBS. All of these techniques are useful in that they widen the number of treatments for mental health problems, and might provide solutions for people who do not respond to common treatments. Many also have a key advantage in that they can target specific brain processes directly, meaning they could be optimised for specific patients based on their brains.
Why is the US seeing rising rates of mental health conditions, particularly in young people?
CN: Nobody knows—even if they tell you they do. I think we have to be very careful about correlation and causation in this area: many people point to things that correlate—like increased use of social media—when there is shakier evidence for a causal role. One factor that certainly plays into it is increased access to diagnoses. A young person with depression fifty years ago may not have identified their symptoms and gone to their doctor for help. This is clearly a good thing, people are getting the help they need. There might also be changing labels: what we define as a disorder has changed across time, and some disorders have now broadened in their scope, or been labelled for the first time more recently. And I am also interested in theories that our changing culture of mental health, knowing that diagnoses and symptoms exist, and seeing our peers be diagnosed with them, might change our interpretations of our own symptoms, perhaps making us focus on them more—particularly at ages where social influence is extremely important, such as adolescence.
And for people with mental health conditions—where will the next solutions come from?
CN: We have a broad arsenal of mental health treatments that work. The problem is that we don’t always know what will work for whom. So one of the most important things that needs to happen is the ability to match people with the treatments that might work for them. My view is that the way to do this is to understand the causes—in the brain and the body—of someone’s poor mental health. These are often quite personal, which is to say, individual: one person with depression may not have the same underlying biological causes as another. But they give us something concrete that can be targeted, either with traditional treatments like therapy or antidepressants, or more novel approaches like psychedelics or brain stimulation. And I think this individualised, targeted approach is the way that we can begin to grapple with the complexity of mental health, and provide better solutions for people struggling with mental illness.
Camilla Nord is director of the Mental Health Neuroscience Lab at the University of Cambridge, where she is an assistant professor of cognitive neuroscience. The Balanced Brain: The Science of Mental Health is her first book. She lives in Cambridge, England with her wife, Rebecca, and daughter, Ottoline.