Vitamin D deficiency in adults does not necessarily lead to difficulty sleeping, and there are a variety of reasons for difficulty sleeping.
Vitamin D deficiency in adults is associated with difficulty sleeping, but only indirectly. Vitamin D deficiency can affect melatonin production to a certain extent, thus indirectly affecting sleep, so even if vitamin D deficiency does not necessarily lead to difficulty sleeping.
Difficulty in falling asleep has many causes, the main causes are environmental factors, psychological factors, physiological factors, disease causes, drug factors, lifestyle and so on.
If you have difficulty sleeping, it is recommended that you consult a doctor for standardized diagnosis and treatment, and do not take medication on your own to avoid delaying your condition.