Talking Changes Minds: the Effect of CBT on Depression

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Researchers recently examined the effects of cognitive behavioural therapy (CBT) on brain functioning in depressed patients and found that the psychotherapeutic approach made actual changes in the brain [1]. The study was published in the journal Social Cognitive and Affective Neuroscience.

CBT is often referred to as a “talking therapy”, designed to reduce distress through changing thoughts and behaviours that are linked to difficult feelings [2]. It seems that those changes to thoughts and behaviours also effect a change in brain activation.

Depression is enormously common. A multinational study revealed a “lifetime prevalence” (the number of people who, up until the study was conducted, had ever had depression) of 14.6% across the “high income” countries included in the study, that is Belgium, France, Germany, Israel, Italy, Japan, Netherlands, New Zealand, Spain and the United States [3]. Depression is not only damaging at a social level with time lost from work, potential impacts on ability to care for children, cost of treatment and social care, but also potentially enormously destructive to an individual and family’s life. Finding good treatments for depression is essential. As is understanding how depression and the treatments work in order to make treatment as efficacious as possible. CBT has good evidence to support its use in treating depression and is at least as good as other non-drug treatments for depression [4]. Indeed, in the UK, CBT is the main recommended treatment for depression as outlined by the National Institute for Clinical Excellence [5].

The causes of depression are complex and likely to include genetic, neurological, environmental and developmental learning and influences, impact of relationships and family as well as thoughts and behaviours. Researchers have found changes in the brain’s activity in relation to the “self-referential bias”.

These biases increase low mood and create a vicious circle. Self-referential bias is when these thoughts are around oneself. Self-referential bias is associated to greater activity in the medial prefrontal cortex (in the middle, towards the front, linked to memory processing), ventral anterior cingulate cortex (bottom part of the anterior cingulate cortex, linked to rational cognition) and amygdala (area associated with emotions). So, if higher activation in these areas is associated with low mood, what happens when you treat the low mood?

Researchers treated 23 depressed patients with group CBT [1]. The patients experienced decreased symptoms of depression. Great news — but what about the brain? The study used functional magnetic resonance imaging (fMRI). Compared to non-depressed, healthy controls, the people with depression had the predicted greater activation in brain areas at baseline when completing a task to judge if words related to them. After treatment, activation of the medial prefrontal cortex and ventral anterior cingulate cortex was increased for positive words but decreased for negative words. Not only was the initial over-activity for negative words removed, there seemed to be a “bias” in brain activity for positive words.

These results demonstrate how CBT is related to changes in brain functioning. Furthermore, the CBT affected the cortical regions, but not the amygdala. This provides evidence that at a neurological level, CBT is altering the more complex thought processes (in the cortex) rather than the emotional processing area itself (the amygdala). Put coarsely, CBT then is affecting emotions via thinking and memory. The study has some limitations: it would be interesting to compare those who had CBT with those who had another type of therapy that is thought to change depression using different mechanisms; the depressed participants were taking medication and although they attempted to control for this, we may be seeing the longer-term impact of the medication; and it is not clear for how long these changes in brain remain and how, as time passes, the brain changes are linked to symptom reduction.

This study makes three important points for us to keep in mind. First, where depression is associated to people engaging in self-referential biases, CBT may be effective and change brain pathways. However, not everyone with depression has this bias as their main or only experience. Second, the changes in brain activation seem to suggest the idea that CBT works by changing thoughts is supported owing to where brain activation changes. Overall this and all studies of this type bring to mind the difficulty of this type of research: the brain is both the creator of our experiences and the subject of the results of our experiences. We must try to cut the Gordian knot to understand whether changes in brain activity cause reduced distress or are the result of reduced distress.

References

1. Yoshimura et al. Cognitive behavioral therapy for depression changes medial prefrontal and ventral anterior cingulate cortex activity associated with self-referential processing. Soc Cogn Affect Neurosci. 2013 Feb 11. [Epub ahead of print]
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2. Brewin CR. Theoretical foundations of cognitive-behavior therapy for anxiety and depression. Annu Rev Psychol. 1996;47:33-57.
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3. Bromet et al. Cross-national epidemiology of DSM-IV major depressive episode. BMC Med. 2011 Jul 26;9:90. doi: 10.1186/1741-7015-9-90.
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4. Wampold et al. A meta-(re)analysis of the effects of cognitive therapy versus ‘other therapies’ for depression. J Affect Disord. 2002 Apr;68(2-3):159-65.
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5. National Institute for Health and Clinical Excellence. (2007). Depression in adults: The treatment and management of depression in adults (CG90). London: National Institute for Health and Clinical Excellence.