Low vitamin D levels have been associated with depression in observational studies. However, large clinical trials, including a major Australian study, have found that vitamin D supplementation does not significantly reduce the risk of depression in the general population.
The relationship may also be bidirectional, as depression can reduce outdoor activity and, consequently, sunlight exposure, potentially lowering vitamin D levels.
If you have been feeling low or a blood test has shown low vitamin D, it’s natural to wonder whether the two are connected. Here is what the research tells us:
- Vitamin D and depression are linked, but low vitamin D hasn’t been proven to cause depression
- Supplements don’t prevent depression, and the evidence for using them to treat it is low-certainty
- Vitamin D is more commonly low in winter, especially in southern Australia
- Medicare covers vitamin D tests only for people in certain risk groups
- If your mood is low for more than 2 weeks, it needs a proper checkup, regardless of your vitamin D level
What Vitamin D Does in the Body and Brain
Vitamin D’s best proven role is supporting your bones and muscles. It helps your body absorb calcium. This keeps bones strong. Your skin makes most of it when sunlight hits you, and you get a small amount from food.
Researchers are also curious about the brain. Scientists have found vitamin D receptors in brain tissue, which is why they have studied whether vitamin D might affect mood. It’s a reasonable question. But receptors in the brain don’t prove that low levels cause low mood, and that is where the evidence gets more complicated.
Does Low Vitamin D Cause Depression?
Low Vitamin D and depression often show up together, but that does not prove one causes the other. Some evidence suggests the link may partly run in the opposite direction. Right now, we can say they are linked. We can’t say low vitamin D causes depression.
Many observational studies have found that people with the lowest vitamin D levels are more likely to have depression. One well-known review in the British Journal of Psychiatry (Anglin and colleagues, 2013) found that people with the lowest levels had somewhat higher odds of depression than those with the highest (an odds ratio of 1.31).
Observational studies can only show that two things go together. They can’t show which one comes first, or whether something else is behind both.
Why the Link Might Run the Other Way
Depression can change daily life in ways that lower Vitamin D. You might go outside less, move less, or eat differently. Less sun means less Vitamin D.
Researchers have also used a method called Mendelian randomisation, which uses natural gene differences to test whether one factor causes another. A UK Biobank study using this method found that depression may lower vitamin D levels, but it couldn’t show that low vitamin D causes depression.
Do Vitamin D Supplements Help Depression? What the Trials Show
In large trials, vitamin D supplements didn’t prevent depression in most people. Smaller studies of people who already have depression suggest a possible small benefit, but the evidence is low-certainty. Supplements aren’t a substitute for depression treatment.
Here is what the main studies found:
Study | Who was studied | What it found |
D-Health (Australia) | More than 21,000 Australians aged 60 to 84 | No overall benefits for depression. A possible benefit in people already taking antidepressants. |
VITAL-DEP (USA) | More than 18,000 adults aged 50 and over | Didn’t prevent depression or change mood scores |
Meta-analysis of 41 trials | People with depression | Small to moderate benefit compared with placebo, but the evidence was low-certainty |
What does this mean for you? Vitamin D isn’t a stand-in for depression treatment. It may matter more if you are truly deficient, which a doctor can check. If your mood has been low for a while, assessment and care for depression should come first.
Vitamin D and Anxiety, Fatigue and Sleep
The evidence here is thinner than it is for depression. Some studies link low vitamin D with anxiety, tiredness, and poor sleep, but the research is mixed and does not show cause and effect. We wouldn’t put much weight on any of it yet.
It is worth knowing that fatigue has many possible causes, including low iron, thyroid problems, poor sleep and depression itself. Tiredness has many possible causes, and low iron can also cause tiredness and low mood, so your GP may check it at the same time.
Who is at Risk of Low Vitamin D in Australia?
Certain factors can increase your risk of vitamin D deficiency, including:
- Living in a southern state, especially in winter
- Spending little time outdoors (for example, office work, illness, or living in aged care)
- Having naturally very dark skin
- Cover your skin for cultural or religious reasons
- Live with obesity
- Have a condition that affects absorption, such as coeliac disease, inflammatory bowel disease, or have had bariatric surgery
- Certain medications
If you are in one of these groups, it does not mean you are deficient. It just means it may be worth having a conversation with your GP.
Vitamin D in Adelaide and Southern Australia in Winter
Winter makes a real difference. The Australian Bureau of Statistics (ABS) National Health Measure Survey 2022-24 found that about 1 in 5 adults (20.6%) were deficient. The rate was 26.!% in winter compared with 15.5% in summer.
Earlier ABS data from 2011-12 showed South Australia, Victoria and Tasmania had the highest winter rates. So if you live in Adelaide or somewhere in the south, you can have a flat winter mood and lower vitamin D at the same time.
The Cancer Council says that in southern states in winter, when the UV Index is below 3, most people need around 2-3 hours of midday sun on their face, arms and hands, spread across the week.
Always use sun protection when the UV index is 3 or above. The free SunSmart app shows the UV index for your area each day.
Is a Vitamin D Test Covered by Medicare?
Medicare covers vitamin D testing only if you meet specific eligibility criteria. Low mood or fatigue alone does not meet the criteria for a subsidised test.
Since November 2014, Medicare has covered vitamin D tests (MBS item 66833) for people at particular risk. Examples include signs of osteoporosis, malabsorption, deeply pigmented skin, long-term lack of sun, certain medicines, and kidney disease.
Your GP decides whether you qualify. Your GP decides whether a test is right for you during a review of your symptoms and pathology, based on your risk factors. If you don’t qualify, you may need to pay for the test yourself.
When Do Vitamin D Supplements Make Sense?
Supplements generally make sense when a deficiency is confirmed, you are at clear risk, and your GP recommends them.
Healthdirect says you should check the amount with your doctor, because too much vitamin D can raise blood calcium levels (hypercalcaemia). Some people also shouldn’t take supplements at all, for example because of certain medical conditions or medicines.
A GP or pharmacist can check what’s safe for you.
Please don’t start or change a supplement on the strength of a mood study you have read online. It’s worth a quick conversation first.
Winter Blues, Seasonal Depression or Something Else?
It’s pretty common to feel low during winter. Shorter days, less sun, and less time outside can all take a toll.
Formal seasonal affective disorder (SAD) is different. Healthdirect rates it as very rare in Australia. For seasonal low mood, light therapy and psychological therapy have evidence behind them, not vitamin D. Approaches like cognitive behavioural therapy (CBT) have stronger evidence than Vitamin D.
If your mood does not lift as the days get longer, it’s worth learning the signs that low mood may be depression.
If your low mood lasts, book an appointment with a GP. You do not need to wait for it to get worse.
Low Mood and Vitamin D: When to See a GP or a Psychiatrist
See a GP
If low mood, tiredness, or poor sleep lasts more than 2 weeks, book an appointment with your GP.
Your GP reviews your symptoms, risk factors, and other possible causes
Such as thyroid, iron, and sleep. Your GP may also look at how thyroid hormones influence mood before putting symptoms down to vitamin D
Vitamin D is tested only if you are in a risk group
Your GP can assess your risk factors and determine whether testing is clinically necessary and covered by Medicare.
If symptoms are moderate, severe, or ongoing
Consider psychology or psychiatry support. A specialist adult psychiatry review can assess your mood, sleep, and other health factors together, and talk through treatment options with you.
Whatever your vitamin D result is, you don’t have to figure out what’s behind a low mood on your own.
If you’re struggling or having thoughts of suicide: Lifeline 13 11 14 | Suicide Call Back Service 1300 659 467 | Kids Helpline 1800 55 1800 (ages 5–25) | In an emergency call 000. For general health advice: healthdirect 1800 022 222.
Frequently Asked Questions
Does low vitamin D cause depression?
Low vitamin D is linked with depression in many studies, but that does not mean it causes it. Depression may also lower Vitamin D, because people often spend less time outdoors. Large trials show supplements don’t prevent depression for most people. So, even when it’s not the single driving force, it’s one piece of a bigger picture.
Can vitamin supplements treat depression?
Some trials in people with depression found a small to moderate benefit, but the evidence is low-certainty. Larger trials in the wider population found no preventive benefit. Supplements are not a substitute for depression treatment. They may matter more if you are truly deficient, so it’s best to talk to your GP.
Is a vitamin D test covered by Medicare?
Only if you meet specific criteria. Medicare covers testing (MBS item 66833) for people at particular risk, such as those with signs of osteoporosis, malabsorption, deeply pigmented skin, or kidney disease. Low mood or tiredness alone isn’t listed. Your GP decides, and you may pay yourself if you don’t qualify.
Can low vitamin D cause anxiety?
Some studies link low vitamin D with anxiety, but the evidence is thinner and mixed than it is for depression. Nothing shows that low Vitamin D causes anxiety. Anxiety has many causes, including stress, health conditions and sleep. If worry is taking over your days, a GP can help you work out why.
How much sun do Australians need for Vitamin D in winter?
The Cancer Council says that in southern states in winter, when the UV index is below 3, most people need around 2-3 hours of midday sun on their face, arms, and hands each week. Always use sun protection when the UV index is 3 or above and check the SunSmart app.
Who is most at risk of Vitamin D deficiency?
People living in southern states in winter, those who spend little time outdoors, and people with naturally very dark skin are at a greater risk. So, are people who cover their skin, live with obesity, have conditions affecting absorption, or take certain medicines at greater risk? Your GP can talk through your own risk.
Can you take too much vitamin D?
Yes, too much vitamin D can raise blood calcium levels (hypercalcaemia), which can make you unwell. That is why health experts advise checking the amount with your doctor first. Some people shouldn’t take supplements at all, so check with a GP or a pharmacist before starting one.
Is winter low mood the same as seasonal affective disorder?
Not usually. Feeling lower in winter is common, but HealthDirect describes formal seasonal affective disorder as very rare in Australia. Light therapy and psychological therapy such as CBT have evidence for seasonal depression. If low mood lasts 2 weeks or more, you should see a GP.
