Several studies show an association between schizophrenia and low levels of vitamin D. To date, there are only few studies about the prevalence of vitamin D deficiency in patients with bipolar disorder. We hypothesized that vitamin D deficiency is less common among patients with bipolar disorder than among patients with schizophrenia or schizoaffective disorder. A second hypothesis is that vitamin D deficiency is more prevalent among patients with schizophrenia, schizoaffective disorder, or bipolar disorders than among the general Dutch population.
Most studies have been conducted with hospitalized patients; in this study, we only included outpatients.
All outpatients of a center for bipolar disorders and all outpatients of 3 flexible assertive community treatment teams were asked to participate in this cross-sectional study.
We included 118 patients with bipolar disorder and 202 patients with schizophrenia or schizoaffective disorder. Vitamin D levels were deficient in 30.3% (95% confidence interval, 25.5–35.6) of the cases. The type of psychiatric disorder was not a predictor of vitamin D deficiency. The absolute difference in risk of deficiency between the study population and the Dutch Caucasian population was 23.8% (95% confidence interval, 18.3%-29.3%).
In this study, vitamin D deficiency was 4.7 times more common among outpatients with bipolar disorder, schizophrenia, or schizoaffective disorder than among the Dutch general population.
Given the high prevalence of vitamin D deficiency, we believe that outpatients with bipolar disorder, schizophrenia, or schizoaffective disorder should be considered at risk of having low levels of vitamin D. Annual measurement of vitamin D levels in psychiatric outpatients with these disorders seems to be justified to maintain bone health, muscle strength, and to prevent osteoporosis.
From the *Department of Severe Mental Illnesses, Mental Health Care Organisation Noord-Holland-Noord, Alkmaar; †Department of Severe Mental Illnesses, Mental Health Care Organisation Noord-Holland-Noord, Heerhugowaard; ‡Centre for Bipolar Disorders, Mental Health Care Organisation Noord-Holland-Noord, Alkmaar; and §Department of Research & Monitoring, Mental Health Care Organisation Noord-Holland-Noord, Heerhugowaard, The Netherlands.
Received October 13, 2015; accepted after revision August 12, 2016.
Reprints: Remco Boerman, MANP, CNS, FACT Wijkteam Alkmaar Noord-Oost, Department of Severe Mental Illnesses, Mental Health Service Organisation North-Holland-North, Oude Hoeverweg 10, 1816 BT Alkmaar, The Netherlands (e-mail: firstname.lastname@example.org).