Cognitive behavioural therapy (CBT) is a type of talking therapy that's used to treat a wide range of mental health problems, from depression and eating disorders to phobias and obsessive-compulsive disorder (OCD). It recommends looking at ourselves in a different way that might prove useful for all of us in everyday life. But what happens to our brains when we have CBT?
CBT is based on the idea that problems aren't caused by situations themselves, but by how we interpret them in our thoughts. These can then affect our feelings and actions.
For example, if someone you know walks by without saying hello, what's your reaction?
You might think that they ignored you because they don't like you, which might make you feel rejected. So you might be tempted to avoid them the next time you meet. This could breed more bad feeling between you both and more "rejections", until eventually you believe that you must be unlikeable. If this happened with enough people, you could start to withdraw socially.
But how well did you interpret the situation in the first place?
CBT aims to break negative vicious cycles by identifying unhelpful ways of reacting that creep into our thinking.
"Emotional reasoning is a very common error in people's thinking," explains Dr Jennifer Wild, Consultant Clinical Psychologist from Kings College London. "That's when you think something must be true because of how you feel."
CBT tries to replace these negative thinking styles with more useful or realistic ones.
This can be a challenge for people with mental health disorders, as their thinking styles can be well-established.
How do we break negative thinking styles?
Some psychological theories suggest that we learn these negative thinking patterns through a process called negative reinforcement.
For example, if you have a fear of spiders, by avoiding them you learn that your anxiety levels can be reduced. So you're rewarded in the short term with less anxiety but this reinforces the fear.
To unlearn these patterns, people with phobias and anxiety disorders often use a CBT technique called graded exposure. By gradually confronting what frightens them and observing that nothing bad actually happens, it's possible to slowly retrain their brains to not fear it.
Primitive survival instincts like fear are processed in a part of the brain called the limbic system. This includes the amygdala, a region that processes emotion, and the hippocampus, a region involved in reliving traumatic memories.
Brain scan studies have shown that overactivity in these two regions returns to normal after a course of CBT in people with phobias.
What's more, studies have found that CBT can also change the prefrontal cortex, the part of the brain responsible for higher-level thinking.
So it seems that CBT might be able to make real, physical changes to both our "emotional brain" (instincts) and our "logical brain" (thoughts).
Intriguingly, similar patterns of brain changes have been seen with CBT and with drug treatments, suggesting that psychotherapies and medications might work on the brain in parallel ways.
Of all the talking therapies, CBT has the most clinical evidence to show that it works.
Studies have shown that it is at least as effective as medication for many types of depression and anxiety disorders.
But unlike many drugs, there are few side effects with CBT. After a relatively short course, people have often described long-lasting benefits.
"In the trials we've run with post-traumatic stress disorder [PTSD] and social anxiety disorder, we've seen that even when people stop the therapy, they continue improving because they have new tools in place and they've made behavioural and thinking style changes," Dr Wild explains.
CBT may not be for everyone, however.
Since the focus is on tackling the here and now, people with more complicated roots to their mental problems which could stem from their childhood, for example, may need another type of longer-term therapy to explore this.
CBT also relies on commitment from the individual, including "homework" between therapy sessions. It can also involve confronting fears and anxieties, and this isn't always easy to do.
Ultimately, as with many types of treatment, some people will benefit from CBT more than others and psychologists and neuroscientists are beginning to unravel the reasons behind this.