Anyone interested in taking part in the study can find out more information here:

Researchers looking into the effectiveness of outdoor swimming to help people reduce symptoms of depression, say the trial results are “promising” as they begin the next stage.

The team from the Sussex Partnership NHS Foundation Trust and the University of Portsmouth carried out a feasibility trial last year involving 87 people with mental health difficulties. The first part of this project was to see if people would sign up to take part, and also whether they remain engaged in the study to the end. 

Outdoor swimming has been hailed over the past few years as a way to improve health and wellbeing, but this is the first official clinical trial to explore the benefits of the activity in adults with depression. 

They are now recruiting more participants to take part in a larger randomised control trial (RCT) at 15 sites in England, to determine if those with mild to moderate depression benefit from an outdoor swimming course and explore reasons why any changes occur.

The two-year and a half year study, called OUTSIDE, has been funded by the National Institute for Health and Care Research (NIHR). It will involve 480 adults with symptoms of depression. Some participants will be given an 8-session outdoor swimming course in addition to usual care, and then compared to a control group who are receiving their usual care. 

Researchers will explore whether the sessions lead to greater reductions in the severity of depressive symptoms and anxiety up to 38 weeks after the trial. They also want to see if it leads to greater improvements in mindfulness, and be a safe and cost-effective intervention to run.

Dr Heather Massey, from the University of Portsmouth’s School of Sport, Health and Exercise Science and Extreme Environments Laboratories, is co-leading the study. She has been a keen open water swimmer for years, having completed a number of long-distance relay and solo swims including a solo swim of the English Channel.

She said: “While the trial was only a preparatory study, the results were really promising. We reported reductions in symptoms of depression and anxiety in the outdoor swimming group compared with the control group, and there was a lower number of them seeking depression-specific therapy post-treatment and at follow-up. The use of antidepressants and sleeping tablets, on average, also reduced more. 

“Our next task is to see if a full-scale randomised control trial produces similar results. If we can demonstrate outdoor swimming is a viable and cost-effective treatment for depression, it has the potential to be rolled out across the UK.”

Hannah Denton, Principal Counselling Psychologist at Sussex Partnership NHS Trust, added: “After many years and lots of hard work, it is really exciting that this project is finally happening! It will be interesting to find out more about how outdoor swimming can impact on mental health, and if we find it is beneficial, then hopefully this research will result in more opportunities for people to take part.”

Before the pandemic, the number of adults experiencing moderate to severe depression in the UK was 1 in 10, but this doubled, to nearly 1 in 5 between March and June 2020.

There is emerging evidence to suggest that regular open water bathing could have a positive impact on a person’s mental health. Immersion in cold water is believed to reduce stress levels and generates a greater sense of wellbeing.

Clara Strauss, Deputy Director of Research at Sussex Partnership and Professor of Clinical Psychology in the University of Sussex School of Psychology, said:  “This is the first large trial of its kind that will tell us if outdoor swimming is helpful for people living with depression. If it is, this could increase the range of options available to people as they find their path to recovery.”

Previous research by the University of Portsmouth team and their collaborators found swimming outdoors may be associated with improvements in wellbeing. An observational study in 2020 found improvements in mood in a healthy sample with no declared mental health issues. 

In a separate study in 2022, 53 participants with a range of depression severity levels, participated in an outdoor swimming course (8 sessions) on the North Devon coast. A post-study questionnaire found 81 per cent of participants felt ‘recovered’, and 62 per cent showed ‘reliable improvement’ to their mental wellbeing.

“Outdoor swimming offers the opportunity for exercise in an outdoor or natural environment but with the added component of cold-water immersion – or CWI”, added Dr Massey.

“There are a number of physiological responses that occur when getting into cold water; these include the cold shock response which occurs as you get in. This is known to cause problems for some people with underlying health conditions, particularly some with serious heart conditions. 

“However if the right precautions are taken, we also think it may be linked to reducing the experience of low mood and symptoms of depression.”

Swimming sessions will take place at locations in North Maidenhead, Sunderland, Windermere, Nottingham, Cambridge, Bristol, Bradford, Manchester, Woking, London, Southend-on-Sea, Maidstone, Brighton, and Lymington and Penzance (a full list of locations can be found in the Notes to Editor).

They will include a mix of sea swimming, lakes, and semi-heated outdoor pools. Each course can facilitate up to 10 people, so the team will operate on a first come first serve basis. 

The study will begin in the summer months, when the water is warmer. Participants will be medically screened before being accepted to take part, and a team of medics will be on hand throughout the study to ensure their safety.

Richard Williams, 41, from Worcestershire took part in the first study at the Lenches lakes in Evesham. He said: “I was a little anxious going into the trial, because I’d never done anything like it before.

“I also felt guilty about seeking help at the time, because I felt like I was beginning to finally get my life back on track. I realised when I started the trial, that the others also had imposter syndrome, and felt like they weren’t deserving of help or needed it as much as others. It doesn’t matter who you are, or what you’re dealing with; if you don’t feel yourself, you should ask for support.”

For years Rich went through bouts of depression and anxiety, and turned to alcohol to find a release. In 2022, he attempted to take his own life. 

“I was at a real low point in my life, and felt completely alone”, he explained.

“After hitting rock bottom I decided to reach out to the Samaritans charity and eventually felt ready to go home and work on myself. I began therapy, and that’s how I found out about the cold water immersion study.

“I was a person who could never actually go in the sea, even in the summer. But during the course and the training you learn how to get past that initial shock and enjoy the euphoric feeling of being immersed in cold water. I’ve never been able to meditate properly or relax because there’s so much going around my head, but in the water it’s just peace and you become more with nature.

“It has completely changed my life. I’m swimming twice a week, in a cold tub every day and even signed up to an Ironman! So I’ve gone from a recovering alcoholic and recluse, into firing on all cylinders now, and wanting to help others and spread the word.”

Anyone interested in taking part in the study can find out more information here: