Seasonal affective disorder and your eyes

In a nutshell: Light exposure genuinely affects mood, and it happens through your eyes. Light hitting the retina helps set your body clock and influences serotonin and melatonin, two chemicals closely linked to mood and sleep. Less daylight in autumn and winter is one of the main triggers behind seasonal affective disorder (SAD), also known as ‘winter depression’. It’s not the only factor, and it’s not something glasses alone can fix, but understanding the eye-light-mood link can help you make small, sensible changes that support how you feel.

Seasonal affective disorder (SAD) is a type of depression that follows a seasonal pattern, usually starting in autumn and easing off by spring. The NHS estimates that around 2 million people in the UK experience it each year, with some studies putting the figure closer to 1 in 15 people.

Seasonal affective disorder symptoms vary from person to person, but the most common signs include:

• A low mood that lingers for weeks, not days
• Less energy and motivation, even for everyday tasks
• Sleeping more than usual but still feeling tired
• Craving carbohydrates and gaining weight
• Finding it harder to concentrate or feel sociable

SAD isn’t the same as simply feeling a bit flat when the clocks go back. It’s a recognised form of depression, and it’s treatable.

It starts with the retina, the light-sensing layer at the back of the eye. As well as the cells that let you see, the retina has specialised light-sensitive cells that don’t contribute to vision at all. Their job is to tell the brain how bright it is outside.

That signal travels to a part of the brain called the suprachiasmatic nucleus, which works as your internal body clock. It uses light levels to time when the pineal gland releases melatonin, the hormone that makes you feel sleepy. Melatonin rises when light drops and falls when light increases, which is why dark winter mornings can leave you feeling groggy long after you’re supposed to be awake.

Light exposure is also linked to serotonin, a neurotransmitter that affects mood, appetite and sleep. Research suggests serotonin activity tends to be lower when daylight is scarce, which lines up with the low mood and fatigue reported in SAD.

So, in short: it’s not a metaphor when people say winter light ‘affects the mind’. There’s a direct, physical pathway from the eyes to the brain systems that regulate mood and sleep.

Reduced daylight is one of the most established seasonal affective disorder causes, but it’s rarely the only one. Genetics, existing mental health and how sensitive someone’s body clock is to light all play a part. Location matters too; SAD is more common further from the equator, where winter daylight hours are shorter.

Researchers are also still investigating why some people’s eyes and brains respond differently to the same light conditions. It’s an active area of study, not a fully settled one, so treat any single explanation with a little caution.

For many people, yes. Light therapy involves sitting near a specially designed lightbox, typically for 20–30 minutes in the morning, at a brightness far higher than ordinary room lighting. Some clinical reviews report meaningful improvement in the large majority of diagnosed cases when it’s used consistently throughout autumn and winter.

A few practical points if you’re considering it:

• Morning use tends to work better than evening use
• Look for a lightbox designed specifically for SAD, not a standard desk lamp
• Speak to a GP first if you have an eye condition, migraines, or take medication that increases light sensitivity

It’s a support, not a replacement for other treatment your GP recommends

Winter doesn’t just affect your mood; it puts extra demands on your eyes, too. Good winter eye care covers two separate things: getting enough light for your body clock, and protecting your eyes from the season’s drier, harsher conditions.

1. Making the most of daylight

You don’t need special equipment to start. Small, consistent habits make a real difference:

• Get outside earlier in the day. Even overcast daylight is far brighter than indoor lighting.
• Sit near a window when you’re working or eating, rather than in the darkest corner of the room.
• Keep indoor lighting brighter through winter; dim, warm bulbs can work against you at this time of year.
• Take regular breaks from screens, especially during darker afternoons when eye strain and low light combine.

If glare or harsh artificial lighting bothers your eyes indoors, anti-glare lenses or blue light glasses can make screens and office lighting easier on the eyes during the months when everyone spends more time indoors.

If you move between dim indoor rooms and bright outdoor light, light-adaptive lenses adjust automatically, so you’re not squinting outside or straining indoors.

2. Avoid dry eyes in winter

Central heating, cold wind and low humidity all draw moisture from the surface of the eye, which is why dry eyes in winter are so common, even for people who don’t usually notice it. Typical signs are grittiness, redness and eyes that water more rather than less, as they try to compensate.

A few ways to protect your eyes in winter and keep dryness in check:

• Blink deliberately and more often during long screen sessions, and take regular breaks.
• Run a humidifier in rooms with central heating, especially bedrooms.
• Stay hydrated. It sounds simple, but low fluid intake makes dry eyes worse.
• Wear glasses or wraparound styles outdoors to reduce wind exposure during your commute or dog walk.
• Don’t skip UV protection. Low winter sun and glare off wet pavements or snow can be just as harsh on the eyes as summer glare.

If dryness sticks around, an optician can recommend drops or, in some cases, a different lens type or coating that suits your eyes better through winter. It’s also worth booking regular eye tests. It won’t diagnose SAD, but it will rule out other reasons your eyes might feel tired, dry or strained over winter. Also, make sure your prescription is still right for the low-light conditions you’re dealing with.

If low mood, low energy or disrupted sleep is sticking around for weeks, turning up most winters, or making everyday life harder, it’s worth speaking to a GP rather than waiting it out. SAD is a recognised, treatable condition, and a GP can talk through options including talking therapies, light therapy and medication where appropriate.

If you’re struggling right now, Mind and your GP practice are good places to start for support.

FAQs: seasonal affective disorder and eye health

Is seasonal affective disorder (SAD) just ‘winter blues’, or is it more serious?

It’s more than a passing low mood. SAD is a form of depression with a seasonal pattern, and it can be just as disruptive as depression that isn’t seasonal. Some people have mild symptoms, others find it significantly affects work, sleep and relationships.

Can sunglasses or blue light glasses cause or worsen seasonal affective disorder (SAD)?

There’s no evidence that everyday sunglasses or blue light glasses cause SAD. Wearing very dark tints indoors during the darkest months isn’t ideal, since it reduces the light reaching your eyes when you need more of it, not less. Save darker tints for genuinely bright conditions.

Does seasonal affective disorder (SAD) only happen in winter?

Most people experience it in autumn and winter, but a smaller number have a summer pattern instead, with low mood easing as the days shorten.

Do lightboxes need to be prescribed for seasonal affective disorder (SAD)?

No, lightboxes for SAD are available to buy without a prescription in the UK. That said, it’s sensible to check with a GP or optician first if you have an existing eye condition or take light-sensitising medication.

Will taking vitamin D help with seasonal affective disorder (SAD)?

Vitamin D levels often drop over winter, and some people find supplementation helpful for general wellbeing. It’s a different mechanism to the light-therapy pathway, and isn’t a substitute for treatment if you have SAD. Speak to a GP or pharmacist before starting any supplement.

How long does seasonal affective disorder (SAD) usually last?

Symptoms typically build through autumn, peak in December and January, and ease as daylight hours increase in spring. Treatment can shorten how long symptoms feel severe.