Isabel Hardman is assistant editor of the Spectator and author of The Natural Health Service: What the Great Outdoors Can Do for Your Mind. She was diagnosed with post-traumatic stress disorder following events she chooses not to disclose, and has intermittent anxiety and depression. She lives between London and Barrow-in-Furness in Cumbria, and is expecting her first child.

How did you first realise that being outdoors helped your mental health?
“I’ve always enjoyed being outdoors – I grew up in the country, and I was nerdily into gardening as a child. When I got sick, my GP insisted that I got out of the house every day. When she found out I used to do a lot of riding, she said: “Well can you book yourself some riding lessons?” She’d be as interested in what I was doing outdoors as she was in how my medication was working.

But it was on my second bout of sickness leave that I really began to focus on what nature could offer. This was during the snap election in 2017, which I was too ill to cover. I made myself go for a walk every day and I started to notice all the wildflowers growing outside our house, and thought: “Why don’t I make a note of everything I see and photograph them?”

I was in Cumbria, which is one of the best places in the country for wild orchids, and I discovered that there was a site not that far from me. I got so immersed in looking for these plants, which are quite hard to find, and the concentration required meant I wasn’t thinking about all the corrosive stuff.

Of everything you tried – running, hiking, wild swimming, forest bathing, and more – what worked best?
Cold-water swimming has made such a difference, not just to my daily mood but my ability to cope with some of the situations that trigger flashbacks and my tendency to get really angry. I’m not naturally an angry person, but I have been very angry at times, and it helps you control your fight-or-flight response, as you are leaping into freezing-cold water.

Once my partner, John [former Labour MP John Woodcock], drove me to Coniston Water after a particularly bad flashback, and he said between me going into the water and getting back out, the difference was “like Izzy is back again”.

Is being outdoors helpful in protecting mental health during the coronavirus pandemic?
It’s going to be really important for people that they have some way of getting out, whether it’s exercising or looking for nature wherever they are. Even in urban areas, it’s there. One of my most exciting botanical finds was in a car park in Glasgow, which was a really rare orchid called a helleborine.

What if you’re quarantined inside?
You can still keep a log of what birds you see out of your window. People always assume that in the middle of a city it’s just pigeons, but you might see sparrowhawks, you might see a peregrine falcon – they nest around tall buildings – and we’ll start to see migratory birds coming back for the spring. You’ll see crows, maybe magpies and jays – they’re very intelligent birds and watching their behaviour is very satisfying. You could also start growing some salads and micro-greens on a windowsill.

Is this your way of managing symptoms, rather than a cure?
Yes, that’s really important. I’ve seen people saying: “Isabel Hardman used to have really bad mental health, but NOW…” Well, I’ve just spent the last two months off sick. It’s about coping strategies, alleviating symptoms, sometimes avoiding a downward spiral. But my illness is still there: it’s inventive, it’s cunning, it’s powerful. It’s really important that we don’t see mental illness as something you have for a bit, and then if you put in enough effort, you conquer it.

What about really severe cases of mental illness?
I didn’t want this to be just another book about how someone went for a walk and didn’t feel quite so depressed; I really wanted to talk about people being sectioned too. When I went to Bethlem [a London psychiatric hospital using gardening as therapy for inpatients] I was really struck by how they had designed their garden so that people didn’t hang themselves in it.

Has pregnancy changed your routine?
I’ve had to adapt – I’d got used to managing un-pregnant me, who could go for a six-mile run! I’ve had to learn new coping mechanisms, and that’s going to be the case once the baby arrives too.

Do you see the stigma surrounding mental health lifting?
I knew people were going to be kind when I said I was unwell, but I think there’s still a lot of stigma for people with severe mental illness – talk to anyone who has OCD or schizophrenia, and they don’t think the stigma is lifting at all. And many people still haven’t really grasped what the symptoms of even really common mental illness are. When I’ve been paranoid or angry it’s: “You’re not really allowed to be ill in that way, you’re allowed to be sad.”

Does focusing on self-help strategies let the government off the hook of funding better mental health treatment?
It’s so easy for politicians to use social prescribing and talk about the importance of outdoor exercise as a way of masking the fact that they’re not investing in beds. But it’s not a case of substituting [treatment] for going for a run, it’s that it’s part of your treatment. I don’t want people to think I’m suggesting this as an alternative, but just as physiotherapy is really important in some physical conditions, these sorts of things are an important part of recovery. We need greater investment across the board for mental health.

• The Natural Health Service: What the Great Outdoors Can Do for Your Mind is published by Atlantic Books (£16.99). To order a copy go to guardianbookshop.com. Free UK p&p over £15