The third Monday in January is often referred to as Blue Monday– otherwise known as the most depressing day of the year. Coined by psychologist Cliff Arnall in 2004, the date was calculated by factoring in the combination of bleak weather, post-Christmas blues, financial struggles and low motivation. This year it falls on 17 January.

But for many, feeling low during the winter months isn’t limited to just one day. Instead, it’s a symptom of seasonal affective disorder (Sad) – sometimes known as “winter blues” or “winter depression” – which is experienced throughout the season. 

It is a type of depression that comes and goes in a seasonal pattern, with symptoms including everything from low mood and irritability to feeling lethargic. While it is not fully understood what causes the condition, it's thought that the shorter, darker days during autumn and winter can have a negative impact on your temperament.

According to the NHS, the lack of sunlight experienced during this period can stop a part of the brain called the hypothalamus working properly, which may increase the production of melatonin – a hormone that makes you feel sleepy – decrease the production of serotonin – a hormone that affects your mood, appetite and sleep – and affect your body’s internal clock (circadian rhythm).

Dr Luke Powles, associate clinical director at Bupa Health Clinics, says that it’s important for everyone to look after their mental health, particularly now people are working from home. “It's increasingly common for people to feel cooped up,” he said. "While the commute might’ve been frustrating, it was still a time to get outside. It’s the same with lunch breaks: lots of people are now eating at home, rather than popping outside as they would’ve done when in the office.”

Stephen Buckley, head of information at mental health charity Mind, agrees, adding that anyone working from home and experiencing Sad should “take time to get outside as much as possible.” He suggests “going for walks when you can, spending time in parks or gardens, or simply sitting near a window”.

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It’s crucial then that on Blue Monday, or during the winter months more generally, we consider the best ways to overcome these symptoms. And thankfully there are a number of things that you can try. From starting light therapy to taking up meditation, our expert-approved round-up includes everything you need to add a little bit of brightness to your day.

While coffee might be your drink of choice on a dark morning to give you energy, caffeine has been found to suppress levels of serotonin, a chemical in the brain that is thought to regulate mood, sleep and memory.

Given the reduced exposure to light during winter months, it's likely that levels of serotonin will already be low, so we recommend swapping your morning cup of java for tea, since it'll have less caffeine, but can still help give you a boost. Plus, black, green and oolong tea all contain an amino acid called theanine, which works to improve focus and attention.

In our review of the best plastic-free teas, this Brew Tea Co proper tea earl grey (£7.95 for 40, Amazon.co.uk) came out on top, with our tester praising it for being "refreshing” and “full of flavour and depth”. Even better, the brand is “as transparent and sustainable as they come”, as it uses “whole leaves (not dust, it insists) and is a member of the Ethical Tea Partnership which supports small estate growers”.

Alternatively, Clipper's everyday tea (£3.80 for 100, Ocado.com) wins for its affordable price and great taste. “It’s become one of our go-to every day teas, just like it says in the name, and is by far the most affordable on the list,” our tester said.

While there’s mixed evidence regarding the overall effectiveness of light therapy, Dr Luke Powles suggests investing in a Sad lamp as a way to manage symptoms.

These gadgets work to mimic natural light and are thought to boost levels of serotonin and melanin, delivering short-term positive effects. Plus, they are a "helpful way to banish the winter blues until the days start getting longer again", says Powles. It is recommended that you use a Sad lamp for a duration of 20 to 40 minutes a day.

Read more: 8 best Sad lamps to get you through the dark winter months

To qualify as a Sad lamp, its brightness needs to measure at least 2,500 lux – the brighter the light, the greater the effectiveness.

Using an alarm clock that has a built-in light is also great way to start the day, helping you to wake up feeling refreshed. Dr Jaya Gowrisunkur from the Priory Wellbeing Centre in Harley Street suggested a Lumie alarm clock. The Lumie bodyclock shine 300 (£108.99, Amazon.co.uk) took the top spot in our guide to the best light-up alarm clock thanks to its great functions and design.

Gowrisunkur noted the importance of a regular wake-up time for managing symptoms, meaning this alarm clock could help you get into a good, healthy routine.

The real beauty of the bodyclock, though, is that the sunset feature can also be used at the end of the day to help you wind down, and it can play sounds to help you fall asleep. This is considered a fantastic complement, rather than an alternative, to a lightbox when treating Sad.

Dr Powles suggests that brightening the environment you work from home in can work to alleviate symptoms. too. Consider this Beurer TL 45 perfect day daylight (£79.99, Johnlewis.com), which was the best buy in our review of the best Sad lamps.

It has three settings – relax, active and therapy, with the latter mimicking midday light, when in this mode, the lamp should be placed about 20cm from you for best results. “We can attest this feels very brilliant and definitely made us feel, well, sunnier after using it,” praised our writer.

"Research shows that physical activity can be as effective as antidepressants in treating mild to moderate depression," says Buckley and, while it can prove beneficial to some, it’s important to acknowledge that exercise isn’t always an option or the right solution for everyone.

However, it can be a good place to start and Dr Gowrisunkur suggests getting out into natural surroundings like the local park can be beneficial. This can be in the form of a long walk, run or simply spending time in the garden if you have one. If going for a light evening jog in the great outdoors appeals to you but you're new to running and not sure where to begin, check out our guide on how to get started, which provides expert advice on everything you need to ace it.

Read more: 8 best trail running shoes for women to tackle all terrains

Whether you're just starting out or a keen marathon runner, a decent kit that will keep you warm during the winter months and help you go the extra mile is essential.

In our round-up of the best women’s running leggings, Lululemon fast and free high-rise tight 28in (£108, Lululemon.co.uk), with our writer noting that these “sweat-wicking, quick-drying, running-specific leggings are undoubtedly the best on the market”.

“With two side drop-in pockets to fit your phone, plus five waistband pockets, you can stash your tech and mid-run snacks with ease – and they never fall down,” our tester added.

The adidas terrex agravic trail running tights (£70, Adidas.co.uk) were a big hit in our round-up of best men's running tights with our writer noting that they are their “go-to for all-terrain exploring”.

“The tights are made from a stretchy and breathable blend of polyester and elastane,” noted our writer, but the nylon front blocks are what made them a “standout”. “Not only does the hard-wearing fabric keep your thighs warm from any gusts of wind, but they offer added protection from any brambles or overhanging foliage that might be blocking your path,” they added.

If factoring a run into your day isn’t for you, Dr Powles advises you take "regular breaks and try to go outside during these times, whether for a quick stroll around the block or a longer walk". This is because a lunchtime stroll can have the same benefits as two and a half hours of light treatment, even on a cloudy day.

Read more: 10 best hiking shoes for women that make treks a walk in the park

Doing this in the drizzle might not seem appealing, but it's proven to help, so it's prime time to invest in a new waterproof jacket that'll keep you warm.

In our review of the best waterproof jackets for women, the Fjallraven high coast hydratic jacket W (£230, Fjallraven.com) won best buy for looking smart but also being “technical enough to take mountaineering or on a long bike ride”. “It’s extremely light at just 281g and packs down small if you need it to,” our tester said. “It was the most breathable activewear jacket we tested – the two-way zip added even more ventilation.”

Similarly, yoga can certainly help with feeling calmer. If you’re new to it, try following a session with Yoga With Adriene, one of the biggest yoga YouTube channels, and invest in a new mat so you have a reliable foundation. We recommend picking up the Yogi Bare lunar paws (£74.95, Yogi-bare.co.uk), which won best buy in our round-up of the best yoga mats.

“At 4.2mm thick, the mat had that tiny bit more padding, which makes a difference by the end of a longer practice,” our tester said. “We didn’t slip once, it’s decently wide (66cm), and we found the mat equally good for vinyasa and hatha yoga.”

When asked how to keep Sad symptoms at bay, Dr Gowrisunkur advised "investing in things that will improve sleep quality" so that you wake up with more energy. This is particularly important since disturbances of sleep have been found to be a key characteristic of Sad.

When it comes to a new set of pillows – something that Gowrisunkur notes as being important – that provide exceptional support, the Brook and Wilde marlowe pillow (£229, Brookandwilde.com) took the crown in our round-up. Described as “one of the best pillows our reviewer has ever slept on”, it’s ideal for side and front sleepers, and is “generously stuffed with a combination of feathers and down”.

While buying a new mattress might seem extravagant, it could help you get a better night’s sleep and ensure you feel rested for the day ahead. For an instantly comfortable night go for the Eve Sleep premium hybrid (£733, Evesleep.co.uk), which won best buy in our guide to the best mattresses.

Made with a combination of memory foam and springs, our reviewer said the mattress is “next level”, especially for people who sleep at least part of the night on their backs. “It also gets 10 out of 10 from us on breathability, comfort and support, being just slightly firmer than medium,” they added.

Alternatively, there are plenty of more affordable sleep solutions worth trying, including the This Works deep sleep pillow spray (£19.50, Thisworks.com), which featured in our guide to the best sleep aids.

“This Works claims that a study found 89 per cent of users fell asleep faster than normal, and while that’s a big promise, it definitely helped us,” our tester said. “It’s hard not to feel relaxed when inhaling its blend of chamomile, vetivert and lavender, especially when used in combination with breathing or meditative exercises.”

While there are a number of different Sad management techniques – including cognitive behavioural therapy and antidepressants – Dr Gowrisunkur suggests taking up meditation as a first defence.

Research suggests that meditation increases serotonin levels in the brain, which is also the mechanism of action within some of the drugs used to treat Sad. If you've never done it before, practising meditation can be difficult to get into. But, thankfully in recent years, mindfulness has exploded in popularity.

Read more: 8 best sleep apps for tracking patterns, drifting off and waking up gently

In our guide to the best mindfulness apps, the Calm Android and iOS app (Calm, £28.99/year) was heralded as the top choice.

Just as the name suggests, Calm is a portal to peace of mind. With so much variety – from calming bedtime stories to easy-to-follow meditations, and even the option to reflect on your mood each day – the app offers a way for you to unwind and refocus your attention.

Perhaps the best-known meditation app, Headspace, which can be downloaded via Android or iOS (Headpace, £9.99/month), also offers a free 10-part basic course that is perfect for beginners.

The sessions come in three, five or 10-minute chunks that are easy to follow. Andy Puddicombe, the narrator and co-founder, will guide you through breath work and body scanning in a calm and easy-to-understand way. You can then use these exercises within every aspect of your life.

For more information on seasonal affective disorder and the symptoms and treatments available, visit the NHS website.

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Looking for more tips on meditation? Read our guide to everything you need for mindful reflection