Do you live in North America? Then there’s a pretty good chance you’re low on vitamin D.

1. You’re more likely to be depressed.

People with low levels of vitamin D in their blood were more than twice as likely to be diagnosed with depression than those with higher levels, according to a study in the British Journal of Psychiatry that included more than 31,000 participants. The hippocampus and other areas of the brain involved in regulating your mood contain vitamin D receptors, so low levels may affect the ability of these regions to function normally, researchers suggest.

2. You’re less likely to survive cancer.
Cancer patients who have higher levels of vitamin D when they’re diagnosed tend to live longer and remain in remission longer than patients who are deficient, according to a study published in the Journal of Clinical Endocrinology & Metabolism. Researchers found that every 10-point increase in vitamin D levels was associated with a 4% increase in survival among people with cancer. The strongest link between vitamin Dand survival rates were found in patients with lymphoma, colorectal cancer, and breast cancer. In fact, breast cancer patients with healthy vitamin D levels are twice as likely to survive the disease as patients with lower levels, reports the journal Anticancer Research.

3. You’re more likely to develop aggressive prostate cancer.
The risk of aggressive prostate cancer was 4 to 5 times greater in men with low vitamin D levels, according to a study in the journal ClinicalCancer Research. The reason isn’t yet understood, though researchers say that screening for vitamin D deficiency and treating it may become an essential part of cancer care.

4. You have an increased risk of dementia and Alzheimer’s disease.

Adults who were moderately deficient in vitamin D had a 53% increased risk of developing dementia, and those who were severely deficient had a 125% increased risk of the disease compared to individuals with healthy levels, reports a study in the journal Neurology. A deficiency in the nutrient was also associated with up to a 122% increased risk ofAlzheimer’s disease. More research is needed to better understand the connection, but researchers suggest that you face a double whammy as you age: Not only are you more at risk of developing cognitive problems, your skin becomes less efficient at converting sunlight into vitamin D, putting you at an increased risk of deficiency.

5. You may be more likely to have psoriatic arthritis.
About 30% of patients who have psoriasis also have a condition called psoriatic arthritis, in which the immune system attacks the joints causingpain and inflammation. And a recent study found that up to 62% of people with psoriatic arthritis have insufficient levels of vitamin D, reports the journal Arthritis Care & Research. Previous research shows that low levels of D may make inflammatory conditions such as psoriatic arthritis worse, possibly by increasing white blood cell levels.