Vitamin D deficiency in treatment-resistant schizophrenia

Vitamin D deficiency is associated with schizophrenia, although cause and effect are undetermined. Various published findings include low serum levels of vitamin D in people with chronic schizophrenia, elevated risk for schizophrenia in people who as neonates had low blood levels, and increased risk and higher symptom burden in early-psychosis cohorts (1). In a recent study from the Netherlands, whose population resides at latitudes similar to that of most Canadians, 28 people with treatment-resistant schizophrenia, 77% men and 61% Caucasian, who resided in a mental-health facility, underwent plasma vitamin D3 (calcidiol) analysis in April and June of the same year (2). A control group of 29 staff at the residence, mostly Caucasian women, also underwent testing. People using vitamin supplements were excluded. The researchers estimated the amount of time each participant spent outdoors daily was 2.3 hours for patients and 0.8 hour for staff.

The mean plasma level of vitamin D3 in April and June was significantly lower in the patients than in the staff, and the increase in plasma concentration during the spring was much less robust in the patients. The prevalence of vitamin D deficiency (as determined by plasma concentration) was 90% in April and 79% in June in the cohort of people with severe schizophrenia; in staff it was 17% in June. Because Caucasians have a greater capacity to synthesize vitamin D when their skin is exposed to sunlight, the investigators did subanalyses and found that non-Caucasian patients had lower mean plasma vitamin D than Caucasian patients, and the non-Caucasian patients’ mean plasma value did not increase during the spring.

The significance of these finding for the mental health of people with schizophrenia is unknown, and the researchers did not describe the medication treatments or the diet of the patients, other than to say it was healthy. Vitamin D is naturally available in eggs, some seafood, and is added to milk in some countries including Canada. The effects of vitamin D deficiency in general are most prominent on bone health. The central nervous system is however rich with vitamin D receptors, and deficiency has been linked to neuropsychiatric illness including depressive disorders and multiple sclerosis. Given that supplementation is recommended for Canadians, especially in the winter when it is impossible for most of us to obtain adequate vitamin D from sunlight, ensuring adequate intake for people with schizophrenia, in particular those in chronic care, is justifiable. The possibility that those with chronic illness cannot synthesize vitamin D with more-than-adequate sunlight exposure suggests that year-round oral supplementation is necessary to prevent or treat deficiency.

References

1. Chiang M, Natarajan R, Fan X. Vitamin D in schizophrenia. Evid Based Mental Health. 2016;19:6-9. Abstract

2. Bogers J, Bostoen T, Broekman TG. Low levels of vitamin D poorly responsive to daylight exposure in patients with therapy-resistant schizophrenia. Nordic J Psychiatry. 2016;70:262-266. Abstract