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Vitamin D deficiency is very common in people with mental health and neurological disorders.

Vitamin D is a vital nutrient and hormone best known for its role in bone development.

But did you know that a lack of vitamin D may also play a role in the development of various mental health disorders, such as obsessive-compulsive disorder (OCD) and depression?

Vitamin D insufficiency and deficiency are quite common in the general population. For instance, as many as 40% of adults are vitamin D insufficient and around 6% are deficient.

And while the fortification of milk with vitamin D in the 1930s improved the situation — and even helped eradicate rickets — deficiency in this important nutrient is still a public health issue.

In particular, low levels of Vitamin D appear in several mental health disorders, including:

  • obsessive-compulsive disorder (OCD)
  • Attention deficit hyperactivity disorder (ADHD)
  • schizophrenia
  • autism
  • depression and anxiety

Obsessive-compulsive disorder (OCD) is a psychiatric disorder in which a person gets caught in an often debilitating cycle of obsessions and compulsions.

Research suggests that a high number of people with OCD have vitamin D deficiency.

A 2017 study found that children and teens with OCD tend to have significantly lower levels of vitamins D and B12 and higher levels of the amino acid homocysteine (an indicator of vitamin deficiency).

These low levels also coincided with symptom severity.

In a 2016 study, researchers compared the vitamin D levels of children with PANDAS-related OCD to those without the condition.

PANDAS is short for Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections. Children may be diagnosed with PANDAS when OCD symptoms suddenly occur after a strep infection.

The study findings show that vitamin D deficiency was much more frequent in the OCD group than in the control group (48.5% vs. 20%).

In addition, children with OCD and low levels of vitamin D also had higher rates of co-occurring ADHD than those without the deficiency (87.5% vs. 52.6%).

As mentioned above, vitamin D deficiency may be linked to attention deficit hyperactivity disorder (ADHD). However, research is mixed.

Some evidence suggests that children with ADHD have significantly lower vitamin D levels than those without ADHD, while another study didn’t find a significant difference between the two groups.

Still, researchers say that treating vitamin D deficiency in this population is important.

It’s long been observed that a higher number of people with schizophrenia are born in winter and spring. This led to the hypothesis that low levels of vitamin D may play a role in its development.

A 2018 study supports this idea, as vitamin D deficiency in infants was linked to an increased risk for schizophrenia in later life.

In addition, vitamin D deficiency is quite high in people with schizophrenia. It’s estimated that 65–70% of those with schizophrenia have low vitamin D levels, and more than half of this population has osteoporosis.

At the same time, people with schizophrenia often have poorer diets and health in general, are less active, and often have other medical conditions — all factors which can affect vitamin D levels.

It’s somewhat unclear whether vitamin D supplementation works in adults with schizophrenia.

Some recent evidence suggests that 12 months of supplementation was linked to fewer symptoms of depression and anxiety in people with schizophrenia. But other research showed no noticeable effects, so the findings are mixed.

A growing body of research suggests that vitamin D deficiency during pregnancy and early childhood is linked to some cases of autism, a neurological and developmental disorder.

Children who have autism — or are likely to develop it — have lower levels of vitamin D at 3 months in utero, at birth, and at age 8 compared to their siblings without autism.

A small 2017 study found that vitamin D supplementation during pregnancy, infancy, and early childhood significantly reduced the expected incidence of autism in children of mothers who already had one child with the disorder. The risk ultimately dropped from 20% to 5%.

Vitamin D supplementation may help in childhood too. Two trials found that high doses of vitamin D improved the core symptoms of autism in about 75% of children with the condition.

There are many individual antidotes of vitamin D helping with symptoms of depression and anxiety. Research also confirms a link in some cases, but the exact mechanism remains unclear.

A 2020 study revealed that vitamin D may play a role in restoring balance between the neurotransmitters GABA (calming) and glutamate (excitatory).

A 2020 review of 61 research papers showed an association between vitamin D and major depression disorder, but whether the deficiency caused the depression or vice versa seems to require further research.

Another 2020 study looked at the effects of giving vitamin D supplements to depressed participants over a 6-month period. The findings show that vitamin D supplements improved anxiety symptoms — but not depressive symptoms — in participants with previously low vitamin D levels.

Vitamin D deficiency is surprisingly common. Research from 2021 suggests that 1 billion people around the world have a deficiency.

Symptoms of low vitamin D may be hard to spot and are often similar to symptoms of other deficiencies or disorders. As mentioned above, low levels of D may also play a role in mental health disorders and other diseases. A 2020 review suggests a deficiency may lead to symptoms of depression.

In children, vitamin D deficiency may have the following symptoms:

People with prolonged and severe vitamin D deficiency may develop a condition called secondary hyperparathyroidism. This causes all of the parathyroid glands to become enlarged and hyperactive.

Symptoms may include:

  • bone pain
  • joint pain
  • muscle pain
  • fatigue
  • muscle twitching
  • weakness

Bone fractures and osteoporosis may also result from chronic vitamin D deficiency.

Between 50–90% of vitamin D is absorbed through the skin via sunlight exposure. To prevent deficiency, researchers suggest 20 minutes of daily sunshine with over 40% of the skin exposed.

Of course, the further away you are from the equator, the harder this becomes.

Diet can provide vitamin D as well. Foods with vitamin D include:

  • Fatty fish: salmon, tuna, swordfish, sardines cod liver oil
  • Vitamin D-fortified dairy or nut milk products
  • Vitamin-D fortified orange juice
  • Egg yolk
  • Beef liver
  • Vitamin D-fortified cereals

Taking regular vitamin D supplements is a good idea for many people.

It’s especially beneficial for those who are older, have darker skin, live in colder climates, or stay mostly indoors, as vitamin D levels are often lower in these groups.

In general, taking regular vitamin D supplements may help reduce cancer cell growth, infection severity, and inflammation (implicated in many mental health disorders). The vitamin is also critical for building strong bones.

For people with mental health disorders, taking vitamin D may help alleviate certain symptoms. It’s likely worth getting your vitamin D levels checked and speaking with your doctor to determine whether vitamin D supplements is a good choice for you.

Vitamin D is a necessary nutrient for promoting brain and bone health. You can get the necessary dose of vitamin D through sunlight, certain foods, or supplements. Although there are many ways to get vitamin D, nearly half of Americans receive an insufficient dosage of vitamin D and billions of people around the world are considered deficient in vitamin D.

Research has revealed that people with mental health disorders are more likely to have vitamin D deficiency or insufficiency. The direct correlation between vitamin D and certain mental health disorders varies.

Some research has found:

  • vitamin D deficiency to be more prevalent in people with certain mental health disorders
  • vitamin D deficiency to play a role in triggering certain mental health disorders
  • vitamin D to help alleviate certain mental health disorder symptoms

Despite there being mixed findings between the relationship between vitamin D and some of the most common mental health and neurological disorders, including OCD, ADHD, schizophrenia, autism, depression, and anxiety, experts agree vitamin D is an essential nutrient that many people are not receiving enough of.

Consider getting your vitamin D checked and speaking with your doctor about ways to get your vitamin D intake to a healthy level. This may be particularly important if you are living with a mental health disorder or have a history of mental illness in your family.