Depression is quite common in the UK. It’s believed to affect as many as one in six adults.

But according to the NHS, it’s not always easy to spot. The health service’s page on the mental health issue reads: “A lot of people don’t realise they’re ill and try to carry on and cope with their symptoms.” As a result, sometimes it takes a loved one’s intervention to help them notice they’re struggling.

The fact it can fly under the radar can cause issues. Consultant psychologist and neuropsychologist Dr Monica Berntsen said “the risk is that [the depression] tends to deepen” without diagnosis.

“It affects relationships, work and physical health, and people lose years believing this is simply how life feels,” she added.

And Dr Tom MacLaren, a consultant psychiatrist at Re:Cognition Health, shared: “I see people who are still going to work and performing well, looking after their families, maintaining relationships and keeping up with their everyday responsibilities, yet internally they are struggling.

“We sometimes refer to this as ‘high-functioning depression’, although it isn’t a formal clinical diagnosis.”

So, we thought we’d speak to experts about the more subtle signs you may have depression.

Dr Berntsen told us that depression doesn’t always feel like sadness – it can feel like “flatness” where things you used to enjoy “start to feel like admin”. This is sometimes called “anhedonia”.

And Dr MacLaren added that it’s a red flag if the things you once loved, like seeing friends or doing a hobby, no longer bring you joy.

If you find yourself “quietly withdrawing from friends while telling yourself you’re ‘just busy’”, Dr Berntsen said it might be worth considering your broader mood.

“Many capable people keep everything running on sheer effort, so the outside looks fine while the inside is exhausted. The brain isn’t broken; it has gone into energy-saving mode,” she said.

Just because you can get the essentials done doesn’t mean you’re mentally healthy – especially if key parts of a healthy lifestyle, like socialising, go out of the window.

Dr McLaren agreed, sharing that people with high-functioning depression may begin “making excuses to avoid seeing friends or family, or finding social interaction increasingly draining”.

Again, this is further proof that depression doesn’t always present solely as sadness. “Some people become more impatient, frustrated or short-tempered, particularly with those closest to them,” revealed Dr McLaren.

For her part, Dr Berntsen cautioned that “irritability and a short fuse” can sometimes be a sign.

You might chalk difficulties with focus down to a long work day. However, both experts told us that depression can make it hard to stay on task, too.

This can manifest as “brain fog and trouble making decisions”, said Dr Berntsen.

You might find yourself “struggling to make decisions, remember things, or focus on tasks that would normally feel straightforward,” Dr McLaren agreed.

“Sleeping badly or much more than usual” often accompanies depression, Dr Berntsen reminded us, while Dr McLaren noted people with depression can also sometimes sleep “too little”.

Research has shown that depression is linked to a more negative self-image.

“Feeling that you are never doing enough, constantly questioning yourself, or experiencing a persistent sense of guilt or inadequacy” could also reveal depression, stated Dr McLaren.

One common side-effect of depression is that it can make seemingly small tasks feel much more onerous and tiring than they ought to be.

You might feel that “everything takes more effort than it should”, said Dr Berntsen.

You might also “continue to do everything you need to do, but feel emotionally disconnected or as though you are simply getting through the day”, said Dr McLaren.

If you’ve felt like this most days for two weeks or more, speak to your GP.

“Tell one person you trust. Small steps help too: a basic routine, a little movement, and seeing people even when you don’t feel like it,” offered Dr Berntsen.

Dr McLaren added: “My biggest message is that you don’t have to be falling apart for your mental health to deserve attention. Just because you are managing to get through the day, going to work and looking after everyone else doesn’t mean you aren’t struggling.”

Lastly, the psychiatrist and psychologist said if you are experiencing thoughts of suicide or feel unable to keep yourself safe, you should seek urgent help through NHS 111, or ring your local crisis team or 999 in an immediate emergency.

• Mind, open Monday to Friday, 9am-6pm on 0300 123 3393.
• Samaritans offers a listening service which is open 24 hours a day, on 116 123 (UK and ROI – this number is FREE to call and will not appear on your phone bill).
• CALM (the Campaign Against Living Miserably) offer a helpline open 5pm-midnight, 365 days a year, on 0800 58 58 58, and a webchat service.
• The Mix is a free support service for people under 25. Call 0808 808 4994 or email help@themix.org.uk
• Rethink Mental Illness offers practical help through its advice line which can be reached on 0808 801 0525 (Monday to Friday 10am-4pm). More info can be found on rethink.org.