Magnesium, Anxiety and Depression

Magnesium has an important role in testosterone production however, it also may play an important role in mental health and wellbeing. Observational studies in humans suggest a link between depression and low levels of magnesium. Animal studies suggest this link may be causal.

https://www.ncbi.nlm.nih.gov/pubmed/19085527
Correlations between recording dietary intake of magnesium and depression - association remained significant after controlling for a range of factors. Anxiety was more weakly associated, and association failed to reach statistical significance once other factors were controlled for.

https://www.ncbi.nlm.nih.gov/pubmed/22695027
Correlation between low magnesium intake and depression in the elderly

Animal study - Magnesium deficiency increased anxiety in mice and causes problems in HPA axis
https://www.ncbi.nlm.nih.gov/pubmed/21835188