Researchers studied over 1,000 college students in Turkey and found that those with low vitamin D levels reported more depression, anxiety, stress, and sleep problems. The study measured vitamin D in students’ blood and compared it to their mental health and sleep quality. Students with low vitamin D had significantly worse scores on depression and anxiety tests, and they also reported more trouble sleeping. Interestingly, even students taking vitamin D supplements still had these problems, likely because their doses were too small to make a real difference. This research suggests that vitamin D might be more important for your mental health and sleep than we previously thought.

The Quick Take

  • What they studied: Whether low levels of vitamin D in the blood are connected to depression, anxiety, stress, sleep problems, and unhealthy eating or exercise habits in young adults
  • Who participated: 1,074 university students in Istanbul, Turkey, with an average age of 20 years old, studied during late winter and early spring when vitamin D levels are typically lowest
  • Key finding: Students with low vitamin D had significantly higher depression, anxiety, and stress scores, plus more sleep problems. Those with low vitamin D were about 2-3 times more likely to have insomnia compared to those with healthy vitamin D levels
  • What it means for you: If you’re a young adult struggling with mood or sleep issues, getting your vitamin D level checked might be worth discussing with your doctor. However, this study shows a connection, not proof that low vitamin D causes these problems—other factors could be involved

The Research Details

This was a cross-sectional study, which means researchers took a snapshot of students at one point in time rather than following them over months or years. They divided 1,074 college students into three groups based on their blood vitamin D levels: deficient (low), insufficient (medium-low), and sufficient (healthy). All students were tested in late winter and early spring, when vitamin D levels are naturally at their lowest because there’s less sunlight. The researchers then gave students questionnaires to measure depression, anxiety, stress, sleep quality, eating habits, and exercise levels. They used statistical analysis to see if students with lower vitamin D had worse scores on these measures.

This approach is important because it allows researchers to see patterns in a large group of people quickly. By studying students during the season when vitamin D is lowest, the researchers could see the strongest possible connection between low vitamin D and mental health problems. The study also looked at whether supplements helped, which is practical information for real people.

Strengths: The study included over 1,000 participants, which is a large sample size that makes the findings more reliable. Researchers measured actual blood vitamin D levels rather than just asking people about their diet. They used validated questionnaires (established tests that are known to be accurate) to measure mental health and sleep. Limitations: This was a snapshot study, so we can’t prove vitamin D deficiency causes these problems—only that they occur together. The study only included college students in one city, so results might not apply to other age groups or countries. The study was done in late winter when vitamin D is naturally low, so results might be different at other times of year.

What the Results Show

Students with low vitamin D reported significantly higher levels of depression, anxiety, and stress compared to those with healthy vitamin D levels. For example, students with deficient vitamin D had depression scores that were noticeably higher than students with sufficient vitamin D. The connection between low vitamin D and these mental health problems was strong and consistent across all three groups (deficient, insufficient, and sufficient). Sleep problems were also significantly worse in students with low vitamin D. Students with deficient vitamin D were about 2-3 times more likely to have insomnia (trouble sleeping) compared to those with sufficient vitamin D. These patterns held true even when researchers looked at different groups separately.

Interestingly, the study found no significant difference in eating habits or exercise levels between groups with different vitamin D levels. This suggests that vitamin D’s connection to mental health and sleep might be separate from its effects on diet and exercise. The researchers also noted that even students taking vitamin D supplements still had high depression, anxiety, and stress scores. However, this was likely because the supplements were too weak—students were taking an average of only 600 IU per day, which is much lower than the doses typically recommended to correct deficiency (1,000-4,000 IU per day).

Previous research has suggested that vitamin D plays a role in brain health and mood regulation, and this study supports those earlier findings. However, most previous studies were smaller or done in different populations. This research is notable because it’s one of the larger studies specifically looking at vitamin D and mental health in young adults. The findings align with growing evidence that vitamin D deficiency may be more common in people with depression and anxiety, though scientists still aren’t sure exactly how vitamin D affects the brain.

The biggest limitation is that this study only shows that low vitamin D and mental health problems occur together—it doesn’t prove that low vitamin D causes depression or anxiety. Other factors (like stress from school, social problems, or genetics) could cause both low vitamin D and mental health issues. The study only included college students in Turkey during winter months, so the findings might not apply to older adults, children, or people in sunnier climates. The vitamin D supplements that students were taking were very low doses, so the study doesn’t tell us whether higher-dose supplements would help. Finally, because this was a one-time snapshot rather than following students over time, we don’t know if improving vitamin D levels would actually improve their mental health.

The Bottom Line

If you’re a college student or young adult experiencing depression, anxiety, sleep problems, or stress, it’s reasonable to ask your doctor to check your vitamin D level (moderate confidence). If your level is low, your doctor might recommend vitamin D supplements—typically 1,000-4,000 IU daily, which is much higher than the doses the students in this study were taking (high confidence that higher doses are more effective than very low doses). However, vitamin D supplements alone probably won’t fix depression or anxiety; they should be part of a broader approach that might include therapy, exercise, and other treatments (high confidence). Don’t assume low vitamin D is the only cause of your mental health problems (high confidence).

College students and young adults (especially those in winter climates or with limited sun exposure) should pay attention to this research, particularly if they’re experiencing mood or sleep problems. People with depression, anxiety, or insomnia might want to get their vitamin D checked. This research is less relevant for people living in sunny climates year-round or those who already have healthy vitamin D levels. People taking high-dose vitamin D supplements (over 1,000 IU daily) may already be addressing this issue. This research should not replace professional mental health treatment—if you’re struggling with depression or anxiety, talk to a doctor or therapist regardless of your vitamin D level.

If you start taking vitamin D supplements, don’t expect immediate improvements in mood or sleep. Vitamin D builds up in your body over weeks and months. Most research suggests it takes 4-8 weeks to see meaningful changes in mood or sleep quality after correcting a vitamin D deficiency. Some people might notice improvements sooner, while others might take longer. If you don’t see improvements after 2-3 months of taking supplements, talk to your doctor—there may be other factors affecting your mental health that need attention.

Want to Apply This Research?

  • Track your daily vitamin D supplement intake (dose and time) alongside a simple mood and sleep rating (1-10 scale) each evening. This creates a personal record to share with your doctor and helps you notice patterns over 8-12 weeks
  • Set a daily reminder to take your vitamin D supplement at the same time each day (ideally with a meal for better absorption). Log it immediately in the app to build the habit and track consistency
  • Use the app to record weekly averages of your mood, anxiety, stress, and sleep quality scores. Compare these to your vitamin D supplement adherence to see if there’s a personal pattern. Share monthly summaries with your healthcare provider to guide treatment decisions

This research shows a connection between low vitamin D and mental health problems in college students, but does not prove that low vitamin D causes depression, anxiety, or sleep problems. Many factors affect mental health and sleep quality. If you’re experiencing depression, anxiety, stress, or sleep problems, please consult with a healthcare provider or mental health professional for proper evaluation and treatment. Do not use this information to self-diagnose or self-treat mental health conditions. Before starting any vitamin D supplements, especially at high doses, talk to your doctor, particularly if you’re taking other medications or have existing health conditions. This study was conducted in one geographic location during winter months and may not apply to all populations or seasons.