Originally published 2018-09-25.
Do traumatic life events cause anxiety and depression? They are one of the strongest known risk factors, but not the only one, and not a guarantee. Large studies show that people who have lived through abuse, violence, sudden loss or other severe stress are much more likely to develop anxiety and depression. Yet many people who experience trauma do not become ill, and many people with depression cannot point to a single traumatic event. Genes, health, money, relationships and, importantly, the way a person processes what happened all play a part.
This article looks at the research behind the "trauma is the biggest cause" headline, what it does and does not prove, how the debate about serotonin has changed, and which popular remedies have good evidence behind them.
What the 2013 Liverpool study found
The headline comes from a study published in PLOS ONE in October 2013 by psychologist Peter Kinderman and colleagues at the University of Liverpool. They analysed online questionnaires completed by close to 33,000 adults in the UK, gathered through a BBC project.
Among all the factors measured, traumatic and stressful life events had the strongest link with symptoms of anxiety and depression. Family history of mental illness, lower income and education, and relationship status also mattered, but less. The most interesting finding concerned what happened in between: the effect of those events was strongly connected to psychological habits, especially rumination (going over problems again and again) and self-blame. Kinderman summed it up by saying that the way a person "thinks about, and deals with, stressful events is as much an indicator of the level of stress and anxiety they feel."
The study had limits. It was a one-off survey, so it showed associations rather than proof of cause. Participants chose to take part online, so they were not a perfect cross-section of the population, and all answers were self-reported. Still, its message fits a large body of other research: stressful experiences raise risk, and how people make sense of them affects how much harm they do.
Why thinking patterns matter, and what helps change them
If rumination and self-blame link trauma to distress, then changing those habits should help, and that is broadly what treatment research shows. Talking therapies such as cognitive behavioural therapy (CBT) teach people to notice spirals of negative thought, question them and respond differently. Trauma-focused therapies help people process memories so that they lose some of their power.
The NHS describes CBT, behavioural activation, interpersonal therapy and counselling as standard options for depression, with guided self-help and exercise among the first steps for milder cases. The practical lesson is hopeful: a person cannot change their past, but there are proven ways to change its grip on the present.
Genes: a risk factor, not destiny
Depression and anxiety do run in families, partly through genes and partly through shared environments. One gene that attracts attention is BDNF, which helps make a protein involved in the growth and survival of brain cells, including in the hippocampus, an area important for memory and emotion. A common variant called Val66Met changes a single building block of that protein.
Animal studies suggest carriers of the Met version may be more sensitive to stress hormones, which could make them more vulnerable after trauma. Human studies, however, have been inconsistent: some link the variant to depression or anxiety, and large analyses have found no clear association with traits such as neuroticism. The fairest summary is that common gene variants each nudge risk slightly, often in combination with life experience, rather than causing illness on their own.
The serotonin "chemical imbalance" debate
For decades, depression was popularly explained as a shortage of serotonin. Most researchers now agree that this simple version does not hold up. In July 2022 an umbrella review in Molecular Psychiatry, led by Joanna Moncrieff at University College London, found "no support for the hypothesis that depression is caused by lowered serotonin activity or concentrations." The same review noted that large studies show stressful life events strongly raise the risk of depression.
Some popular writers have gone further, claiming that antidepressants are a marketing trick or that they lower serotonin and therefore cause depression. Those claims are not supported. The review did not test whether antidepressants work. Antidepressants appear to act through more complex changes in how brain cells function, not by "topping up" a missing chemical. The NHS notes that most people with moderate or severe depression benefit from antidepressants, though not everyone does, and that combining medication with talking therapy usually works better than either alone.
Anyone thinking about stopping an antidepressant should talk to a doctor first. Doses are normally reduced gradually, because stopping suddenly can cause withdrawal symptoms.
Tapping, the gut and other popular remedies
EFT tapping. Emotional Freedom Techniques involve tapping on points of the face and body while focusing on a problem and repeating affirmations. Its proponents describe energy meridians, but there is no scientific evidence that meridians exist, and EFT is widely classed as pseudoscience. Some trials report reduced anxiety, but better-designed studies found it made no difference where people tapped. Researchers attribute the benefits to familiar ingredients the method borrows: facing a painful memory, distraction, slow breathing and positive self-talk.
(The video originally embedded here is no longer available on YouTube.)
The gut-brain connection. It is true that more than 90% of the body's serotonin is found in the gut, and scientists are actively studying how gut microbes interact with the brain. But serotonin made in the gut does not simply travel into the brain, and the human evidence for probiotics as a treatment for depression or anxiety is still small and early. A varied diet with plenty of fibre is good for overall health; it is not a substitute for treatment.
Supplements and sunshine. Low vitamin D and omega-3 intake have been linked with depression in some studies, but the links are inconsistent and supplements have not proven to be reliable treatments. A blood test and a conversation with a doctor are better guides than general advice.
Steps with good evidence behind them
- Move regularly. Physical activity is one of the most consistently supported ways to ease mild to moderate depression and anxiety, and the NHS lists it among the main options for mild depression.
- Protect sleep and routine. Regular sleep, meals and daylight help stabilise mood.
- Stay connected. Isolation feeds rumination; time with supportive people protects against it.
- Notice rumination and self-blame. Writing thoughts down, scheduling "worry time" or practising mindfulness can help break repetitive loops.
- Ask for professional help early. A GP or doctor can discuss talking therapy, medication or both.
A related video from TED, shared on its Facebook page, is embedded below.
Common myths
- "Depression is just a chemical imbalance." It is a complex condition shaped by biology, life events and psychology together.
- "If antidepressants don't fix a serotonin shortage, they don't work." How a treatment works and whether it works are separate questions. Many people are helped by them.
- "Trauma means you will become depressed." Trauma raises risk, but many people recover well, especially with support.
- "It's in your genes, so nothing can be done." Genetic risk is modest and treatable conditions remain treatable.
If you are struggling with low mood or anxiety, talk to a doctor. If you are thinking about harming yourself, contact emergency services or a crisis line in your country straight away.
Sources: Kinderman et al., PLOS ONE, 2013; UCL News, 20 July 2022; NHS: Treatment for depression; Wikipedia: Monoamine hypothesis; Wikipedia: BDNF Val66Met (rs6265); Wikipedia: Emotional Freedom Techniques; Wikipedia: Gut–brain axis; topic first covered in an essay by Joseph Mercola published on Wake Up World.
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