A lack of vitamin D – common in the UK during the autumn and winter months – has been associated with increased symptoms of depression, according to a new study.
Earlier this year everyone in Britain was recommended to take supplements of the vitamin during the darker months. While it is found in a few foods like oily fish, most people get vitamin D from a natural effect on the body caused by sunlight. Low levels are associated with bone conditions such as rickets and osteoporosis, but it can also affect muscle tissue and has been found to be associated with normal levels of dopamine, a chemical linked to mood, in the brain.
In the new study, which was revealed at the International Early Psychosis Association in Milan, scientists tested vitamin D levels among 225 patients being treated for psychotic disorders and another 159 well people.
They found a significant association between low levels of vitamin D and “higher levels of negative symptoms and of depression” among people with psychosis. They also found a significant link to reduced verbal fluency and cognitive impairments.
In a paper in the journal Schizophrenia Research, the researchers, from Norway, suggested vitamin D could be used to help treat patients. “In a clinical setting, this could support vitamin D as adjuvant therapy in treating co-morbid depressions in psychotic disorders,” they wrote.
“The associations between low vitamin D levels and increased negative and depressive symptoms, and decreased [mental] processing speed and verbal fluency are good arguments for planning large scale randomised controlled studies in target populations, in order to reach conclusions about vitamin D's potential beneficial effect in psychotic disorders.”
They are currently running further studies into the effect of vitamin D on the brain using MRI scanners.
In addition to resulting in low levels of vitamin D, a lack of sunlight has also been linked to depression generally.
Seasonal affective disorder, or SAD, is a seasonal form of depression that tends to affect people when the days are shorter. According to the NHS, symptoms include a persistent low mood, feeling lethargic and sleepy, and craving carbohydrates.
Dr Peter Selby, of Manchester University, who has studied vitamin D, said it was plausible that low levels might have a depressive effect. “We know vitamin D levels are important for things like muscle function as well as bone function,” he said. “And muscle function isn’t a million miles removed from nerve function.
“A lot of people with low vitamin D levels … they’ve not quite as much get up and go, they’ve got a few more aches and pains, that sort of thing.”
But he agreed with the researchers that more work needed to be done to establish exactly the vitamin’s effect. “If you are depressive, you are less likely to get out and about, you’re less likely to see the sun [and therefore have less vitamin D],” he said.
“It’s difficult to tell which is the chicken and which is the egg here.”
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