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Why stress? How cortisol can be linked with depression in adolescents

Last year, I wrote a blog on how early life stress can affect how our bodies work and how it can lead to feeling depressed. In particular, I spoke about how being repeatedly exposed to stress can sometimes overcome our coping strategies leading to feeling helpless, and even depressed. This happens when the stress hormone — cortisol, which we produce in response to stress and which helps us cope with it, is no longer efficient at doing its job, meaning its higher levels stay in our bodies. Often, adults with depression have higher levels of cortisol.

I am a Research Psychologist and I am interested in depression in adolescents because that’s when it starts for a lot of young people, and that’s when we should start intervening. Depression in adolescence is a global health concern, being one of the leading causes of death in adolescence, with an estimated up to 11% worldwide prevalence pre-pandemic and 25% prevalence during the pandemic.

Seeing the impact of this condition on young people’s lives, together with my colleagues as part of Identifying Depression Early in Adolescence (IDEA) project, launched by the MQ: Transforming Mental Health Charity, we wanted to understand the risk factors for depression in adolescents and young people worldwide, with the hope of informing more effective intervention strategies. We were particularly driven to do so when we saw that not many studies looked at depression in youth, with the majority focusing on adults.

Now back to cortisol, seeing how it was linked with depression in adults, I delved into the literature to understand whether it was also the case in adolescents and young people, and this is what I would like to talk about in this blog.

Cortisol and depression in adolescence — worldwide perspective

I did a meta-analysis which is an analysis of the pooled results from all the studies available on the topic. I looked for all the scientific studies published worldwide that focused on cortisol as a risk factor for depression in adolescence. It is a powerful tool as it helps us look at patterns in bigger samples, much more than when looking at a single study.

These findings were published this year in Psychoneuroendocrinology so if you are interested to read more about them, you can find them here.

First of all, I found only 26 studies on the topic (compared with hundreds on cortisol in adults)! And, even less, only 3, were done in low-and-middle-income countries (LMICs)!! I mention this because 90% of adolescents worldwide live in LMICs, which means that we barely have any studies done to understand risk factors for depression in most of the adolescents out there! This is a massive research gap and one that needs to be addressed (for all of the researchers interested in the topic, that’s a hint there).

Patterns of cortisol in adolescence — when healthy becomes unhealthy

There are several ways to measure cortisol, which is most often analysed in saliva. We can look at resting cortisol levels right after waking up, in the first hour from awakening (cortisol awakening response), and at different times throughout the day, either individually or altogether to see how it changes throughout the day (diurnal cortisol). We can also look at how we produce cortisol at night from the urine. Then, we can look at cortisol reactivity, i.e., how our body reacts to stress — cortisol stress response. So, what do these measures tell us?

When we are healthy, typically our cortisol would increase when we wake up and our cortisol awakening response will be higher compared to cortisol levels in the rest of the day. This is because we need that “boost” to start the day and as we wind down as the day comes to an end, we are relaxed and ready for bed. When we respond to stress, our cortisol levels rise just enough to cope with the situation, following which they return to baseline. When we experience depression, often what we see is that this pattern is dysregulated, and that self-regulation is disrupted.

Image source: Photo by Erik Karits on Unsplash

And this is what we found in our meta-analysis.

Specifically, adolescents who went on to develop depression showed higher levels of morning cortisol compared to adolescents who did not develop depression at a later stage. What was interesting is that we did not see any difference in morning cortisol levels in adolescents who were already depressed compared with those who were not. This is interesting because it suggests that higher levels of cortisol can be detected before depression develops, almost like a signalling system telling us what might happen next.

In terms of other cortisol measures, we had very few studies to be able to draw strong conclusions. However, it is worth mentioning that few studies reported higher night-time cortisol, cortisol awakening response, and cortisol stress response to be linked with depression. Neither diurnal nor afternoon nor evening cortisol was associated with depression.

As much as what we found gives us a better picture of what might be happening in our bodies before we develop depression, this is only a fraction of the picture, based on a few studies.

As a Research Psychologist, I am curious to understand what sets off the cortisol dysregulation in some but not others and what is the role of the environment in all of this. I guess these are the questions that I will be looking to answer in the future and once I learn more about them, I will most definitely share them with you on this platform!


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