A question about B12 deficiency and insomnia in older people led to a concise summary of the topic in the The New York Times. 

Insomnia is known to have a strong link to depression, and one case study of a severely depressed elderly patient found that treating her B12 deficiency significantly improved her mood.

The results, published in 2009 in The Primary Care Companion to The Journal of Clinical Psychiatry, led researchers to suggest that people with mental disorders such as treatment-resistant depression be evaluated for a B12 deficiency. They also called for large-scale research on the subject.

One of the first broad studies to consider the effects of vitamin supplements on sleep found that, in general, taking them was actually associated with sleep disorders, but no cause-and-effect chain was shown.

Get the whole story at www.nytimes.com